Tuesday, August 24, 2010

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Psychobiology: hormones

In terms of chemical hormones belong to three different categories: •
Peptides and proteins (from a few to hundreds of amino acids)
are hydrophilic and bind to a membrane receptor
oxytocin, ADH, Tropine pituitary, growth hormone, prolactin, insulin, ... • Steroids
(LIPD complex similar to cholesterol)
are hydrophobic, pass through the membrane and combine with a receptor cytoplasmic going to act at the DNA level.
cortisol, aldosterone, androgens, testosterone, ... • Amine
(derived from amino acids with the loss of COOH group)
are hydrophilic and bind to a membrane receptor tyrosine
, ...
Some molecules can play the role of neurotransmitter hormone. For example, norepinephrine is released by some neurons for synaptic communication, but when increta is a hormone from the adrenal glands and interferes with the functioning of muscles, blood vessels, heart, liver cells etc.. Typically, a hydrophilic
hormone has the same function of a synapse indirect, but part of a chain of cellular events increased, so more flexible control.
Most of the time, the secretion of hormones and guided by a negative feedback mechanism . This is a system that tries to maintain a certain variable over time. Many hormones have a common autocrine to the same gland that increti them in order to modulate the release and production. There are also
positive feedback mechanisms, but are rare in biological systems, and occurs when the system emphasizes a change when a variable deviates from a predetermined value (eg the action potential and the mechanism of confinement).

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Psychobiology: elements of Psychobiology

chemical communication within the body regulates many important functions ranging from cell differentiation to the control of behavior ( hormones, prostaglandins , neurotransmitters). The same compound, or other chemical molecules, can be used for communication chemistry between different individuals of the same species or in some cases between different species (pheromones ).

The endocrine system
• chair homeostasis maintaining physiological parameters within set limits.
- Keeps
salt-water balance - Maintains constant blood concentrations
- Check
• Check the energy metabolism functional alterations of the internal
- Reaction to stress
Noradrenaline and adrenaline preparing the 'body to fight-flight.
- Playing In several
periods of the different concentration of androgens in the male finch produces physiological adaptations and behavior. •
has organizational effects on the development
- Development and growth
Bees carry out activities in their hive-dependent hormone concentration YH (youth hormone) which tends to increase with age.
- Sexual Differentiation
Promote the development of secondary sexual characteristics.

In an organism the endocrine system and nervous system working in transmission, but the former has effects that go slower over time, The second speed is limited in time.

Chemical communication is differentiated in relation to the scope of its effect:
-
Synaptic communication is a highly localized synaptic gaps between neurons with neurotransmitters.
- autocrine autocrine
The statement shall provide the neurotransmitter autoreceptors of the pre-synaptic neuron, that is with himself.
- paracrine
A chemical messenger is allowed to spread to other nearby cells and affects the physiology.
> Neuromodulation
Neuromodulatorie synapses are characterized by a wide slot and issue a NT that influence neighboring cells by reducing or enhancing the effect of other NT.
> effects of histamine
Following tissue injury is the release of histamine that has spread locally to:
• Co-ordinate the immune response
• Cause an inflammatory process
• causing hyperalgesia (increased sensitivity to pain)
> paracrine inhibition of insulin and glucagon
; In addition to its antagonistic effects on blood glucose at a systemic level, the two pancreatic hormones, inhibit local mutual secretion.
- Endocrine and neurosecretiva
This type of communication differs from others because the chemical messenger ( hormone) is released into the bloodstream and reaches all body tissues.
cells that produce hormones are almost always grouped in structures called endocrine glands . In the CNS these cells are neurons and spill their contents into the bloodstream. In this case we speak of neurosecrezione .
Although hormones reach all body cells, they respond to the signal only those that have a receptor for quell'ormone. The receptor may be present in the plasma membrane or cytoplasm depending on the chemical nature of the hormone. There are also
exocrine glands (salivary, sweat, etc.) which do not discharge the contents into the bloodstream and are always provided with a duct .
- pheromonal
are chemical molecules that can influence the behavior of conspecifics. Pheromones are often hormones or their metabolites, ie chemical stages of androgens or estrogens. The pheromones
:
• allow the attraction at a distance. Some insects are sensitive to a single molecule of pheromone dispersed in air at a distance of one kilometer.
• Provide information on reproductive status.
• Branding the territory. •
status indicators.
• Tracking. • Inhibition
reproduction.
• Alarm.

- Alloferomonale
Some chemical signals are addressed to individuals of different species. As in
flowers with their perfume invite the insects to spread their gametes.
But they are more cases in which it is imitating the signal of a species by another to cheat.

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endocrinology: fundamentals of psychopharmacology

With drug means any substance that affect the functioning of the SN. In addition to NT, several other psychotropic substances that act on the SN. Among the endogenous substances include the NT, neuromodulators, hormones, II messengers that are created by the body to alter the functioning of the synapse. However, there are exogenous substances that interfere with the functioning of the synapse, including animal and plant poisons and psychoactive substances such as drugs and drugs (drug abuse). The pharmacodynamic

concern the way drugs act on the body. A drug can have two effects on synaptic transmission.
L ' of a NT agonist is a substance that increases the effects.
can act at pre-synaptic synthesis or by increasing the release of NT (poisons) or by increasing the permanence of the NT in the synaptic cleft by inhibiting the reuptake or by inhibiting the enzyme inactivation (drugs).
at post-synaptic site binds to the NT with similar or more intense activity, increases the affinity for NT, enhances the effects of NT.
L ' of NT antagonist reduces or blocks the effect.
The antagonist may act at pre-synaptic inhibition of synthesis by inhibiting the release of NT or NT. A post-synaptic
decreases the affinity of receptor for NT or occupies the active site but not showing effects.
Both agonists antagonists that can bind to the active site of the NT receptor or of the active sites of the receptor sensitive to other endogenous molecules. In many cases it is not yet known endogenous substance that is to interact with these sites. The opiate morphine
was discovered before payment endogenous' s endorphin. More recently have been discovered endogenous substances that bind to the active site of cannabinols , the ' anandamide and 2-AG these endocannabinoids . The
benzodiazepines (anxiolytics) act subclass of GABAA channels selectively.
L ' alcohol increases the action of GABA and inhibits NMDA channels.
L-dopa (parkinson therapy) increases the synthesis of dopamine. The
curare blocks the nicotinic receptors. The
nicotine stimulates nicotinic receptors.
Cocaine and amphetamine block the reuptake of norepinephrine and dopamine. Cocaine in particular the dopamine system and lead to a strong dependency because the dopamine system is linked to pleasure and positive reinforcement. The
cannabinols act on pre-synaptic autoreceptors inhibiting the release of NT. Act on glutammaergico and GABAergic system. The
caffeine increases the release of glutamate. The antidepressants I
generation MAO inhibitors which inactivate the catecholamines in the synaptic cleft. The second generation antidepressants
(Prozac) block the reuptake of serotonin. Some
local anesthetics (eg lidocaine ) act by binding to voltage-gated ion channels of the SNP by limiting the action potential. The pharmacokinetics

is the process by which drugs are absorbed, distributed in the body, metabolized and excreted. 99% of psychoactive substances CNS-active so it must cross the blood-brain barrier and penetrate into the nervous tissue. The exogenous substances are continuously removed by enzyme systems present in blood and especially in the liver and excretion via the urine.
The pharmacokinetics of a substance is highly dependent mode of administration (intravenous, smoked, oral, intranasal, etc.).. Among the factors that determine the speed at which a drug reaches the site of action is the ability to cross the blood-brain barrier and this depends greatly on the lipid solubility of the molecule, because the water-soluble molecules are retained. For example, morphine and heroin within the brain have the same effectiveness of action, however, heroin is much more soluble and has a more rapid and intense.
Regarding the effectiveness of a drug, some drugs are active in small doses, others only at high concentrations. To assess the effectiveness of a drug is administered to different subjects (correcting for body weight) and measuring objectively the effects. This will produce a dose-response curve . This is usually a sigmoid in which there is a minimum to detect the effect, then increases linearly until a dose escalation does not increase the effect.
Most of the drugs has more of an effect. Some are harmful side effects, such as morphine and high doses depresses the respiratory system and causes death by asphyxiation. A good product should have a good therapeutic index, ie the ratio between the dose-response for the desired dose-response for side effects. The distance between the two dose-response is said margin of safety. Technically, the therapeutic index is the ratio of the dose that produces the toxic effect on 50% of the subjects and the dose that produces the desired effect in 50% of subjects. For example, the index is between 2 and 3 for barbiturates and is about 100 for benzodiazepines (valium). This means that is very easy to accidentally make mistakes with fatal consequences dose in the first case in the second.
If a drug is normally administered repeatedly changing its pharmacokinetics.
The most frequent is that of tolerance . With prolonged use its effects are less and less effective and increasing doses. Tolerance is the body's attempt to offset the effects of the drug in order to obtain an optimal level of functioning. In general, the tolerance may depend on many factors, such as the increased capacity of the liver and other mechanisms to metabolize the drug. At the neural level depends on induced changes in the level of synapses. Can be produced channels that have reduced affinity with the drug, may be reduced on the membrane channels, can change the production and inactivation of the second messengers. For all intents and different tolerances occur. For instance, for benzodiazepines, tolerance to the hypnotic effect is very rapid, while the anxiolytic effect tolerance occurs in a minor.
A secondary aspect of the phenomenon of tolerance are the symptoms of withdrawal , ie, effects opposite to those induced by the drug. In fact, the metabolism may have been set for the arrival of a given drug agonist of NT and by the time the pre-synapse always produces less NT.
The effect is the opposite of tolerance awareness, so the drug at doses similar effects increasing. For example, the euphoric effects of cocaine develop tolerance, while the secondary symptoms such as disturbance in the movement undergoes sensitization.
Levin (1979) studied the biological basis of ' placebo effect, ie a dose of a drug is not active but produces measurable effects in the subject.

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Psychobiology: classification of synapses

Electrical Synapses
The plasma membranes are set against each other crack with plasma of 3.5 nm with delays of 0.1 ms.
The action potential is taken directly from the cell pre-synaptic post-synaptic.
He met occasionally in the SN because it is not a typical structure of neurons.
The potential is transmitted through the connexons , much broader than the ion channels, gap junctions in .
not allow the integration of synaptic signals and bi-directional.
are used when needed and speed of transmission when synchronization is required in the activity of most cells.
- excitatory
In the visual system of vertebrates, the retina, in the heart.


Chemical synapses The synaptic cleft distances
neurons from 20 to 50 nm, the delay is 0.5-5ms.
The action potential is converted by the pre-synaptic neuron in neurotransmitter that depolarizes ( PPSE ) or hyperpolarized ( PPSI ) the post-synaptic neuron post-synaptic potential with a PPS. The NT never enters the post-synaptic cell, but only affects the slot.
These differ in the reaction of the post-synaptic neuron.

There is a classification by the morphology of synapses to identify at a glance whether a synapse is excitatory or inhibitory. The
Gray type I (30 nm synaptic cleft, asymmetric membrane specializations, active zones thick and wide, rounded synaptic vesicles, spines often present location and associated dendritic) correspond to excitatory. The Type II
Gray (20nm synaptic cleft, membrane specializations symmetrical active zones and thin not extensive, ovoid synaptic vesicles, spines normally absent and associated somatic location) corresponds to an injunction.

- direct or ionotropic
The NT goes to act on a dependent ion channel transmitter that allows the entry or exit of ions binding to the NT. It is fast enough, however, only one transmission is not sufficient for the development of the action potential.
- Neuro-muscular junction
not worth the classification of Gray because morphologically different from the synapses of the SN.
The post-synaptic membrane ( motor plate) is a muscle fiber in contact with a motor neuron and is much larger than a neural synapses. Membrane specializations are unique in both pre-synaptic neuron (thick filament as the active zone) and in the motor plate (junctional folds). The NT is
acetylcholine and was released only to excite, in amounts 200 times the normal synaptic communication. The channel is called the cholinergic nicotinic receptor.
-
The main excitatory NT glutamate. They are usually associated dendritic and serve hundreds or thousands of PPSE to get a post-synaptic action potential.
- The main inhibitors
NT are glycine and GABA. They are usually associated somatic or axo-axonic the fact that the PPSI is softer than the PPSE and thus the propagation delay is compensated PPSE.
There is a second mechanism called inhibition derivation which acts only when the neuron is excited. In fact, the ECL is close to the Vm, so opening up Cl-channels does not occur until no hyperpolarization Vm changes.
- or indirect or metabotropic G protein-coupled or second messenger
The NT goes to act on a membrane receptor, called membrane receptor associated G protein, which initiates a series of events inside the cell as the last step that have activation of the ion channel. It is much slower but it allows a greater reaction in duration and intensity. The G proteins are membrane proteins that are associated with NT-dependent receptors, which change within and split into three subunits.
Of course there is no single G protein, but of families. The G protein is not specific to neurons, but is typical of communication from other cell types.
The split occurs through the molecule of GTP (guanosintrifosfato) which replaces the GDP in the α subunit. Each subunit assumes
properties and different functions. The α subunit is looking for a target to trigger the reaction. In short
via the α subunit of G protein directly seeks an ion channel. In
Falls II messenger G protein α subunit activates an enzyme that produces a molecule called soluble II messenger that activates a second enzyme which then activates the ion channel. The second messenger functions as a sort of internal NT that can modify cellular metabolism and gene expression of the neuron, so the effect lasts much longer. The messenger molecule
The most common is the ' cAMP (Adenosinmonofosfato cyclic) derived from ATP is modified by the enzyme adenylate cyclase. The cAMP activates protein kinase which transfers a phosphate that ultimately activates the ion channel.

The first characteristic of synapses is the indirect ' amplification effect the NT. In fact, in one molecule of NT open ionotropic channels in metabotropic a molecule of thousands NT opens ion channels to effect the cascade of reactions inside.
The second characteristic of synapses is the indirect ' magnitude of the effect in the cell. The ionotropic effect is not very extensive, in the metabotropic effect extends throughout the neuron.
The third characteristic of synapses is the indirect effect life in the cell. The ionotropic effect is instantaneous, in the metabotropic effect lasts until all the internal reactions are not finished, but it is delayed.

indirect synapses are widely adaptable. In fact, the β subunit may in turn activate other II messenger. Some hormones affect other receptors that give rise to second-messenger cascades that can, for example, inhibit the synthesis of cAMP.
- excitatory
- Inhibitor
- Neuromodulatorie
are usually associated axons.

Integration post-synaptic potential
The electrical activity of neurons depends on the amount of excitatory and inhibitory synaptic signals received, the position where they are located synaptic contacts and constant space and the time constant of the various portions of the neuron. The spatial summation

is almost algebraically, PPS = PPSE - PPSI, to the threshold of action potential. In the spatial summation depends on the geometry of the synapse and space constant.
The efficacy of a synapse decreases with distance, but this varies from cell to cell and in different parts of the same cell. The degree of attenuation signal depends on the space constant, ie the distance at which the value of the PPS is the 37% of its initial value . The constant depends on the section of the dendrite and the resistance of its membrane.

The effect of PPS does not cease immediately after stimulation, in the post-synaptic neuron lasts for a variable period.
The calculation of the duration of the signal depends on the time constant and defines the time after which the PPS decreased by 37% compared to its initial value and varies between 1ms to 20ms.
The temporal summation takes place in dependence on the time constant, the more higher the more it is possible to trigger a potential action.

There are exceptions. Some neurons have a spontaneous firing rate produced by your metabolism. Some dendrites have very large need for riamplificare the PPS, but the transmission is normally elettrotonica.

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Psychobiology: the cycle of neurotransmitter

• Synthesis and storage of NT
The synthesis of low molecular weight is directly in the synapse. Are stored in synaptic vesicles by protein carriers in the tanks.

A summary of the NT with high molecular weight are produced in the soma from the rough endoplasmic reticulum and then elaborated from the apparatus of Golgi. Vesicles, secretory granules containing NT bud and then are transported associated plasma anterograde transport in the synapses. NT
The high molecular weight have been released can not be recovered and must synthesize them again.

Each neuron releases a single type of NT low molecular weight, but it can co-exist a NT peptide. •
Liberation
Once in the synaptic button, the action potential activates the ion channel voltage-gated Ca + + which is in the vicinity of active zones. Football is far more concentrated outside, so it breaks open the cell.
The divalent cation calcium activates the SNAREs mechanism that opens the content of the vesicle flows ( exocytosis) in the synaptic cleft through the fusion pore (0.2ms). The vesicle is embedded with the membrane of the synapse.
Through ' membrane endocytosis in excess is recovered and sent to tanks that create new membranes and fill them with NT. The process takes about a minute.
At the same time the ion approaches the synaptic vesicles that are lagging behind other undock from the cytoskeleton.
In the neuromuscular junction are freed up to 200 vesicles in the CNS at most 2 for each action potential.
For molecules with high molecular weight exocytosis of secretory granules does not occur at active zones and requires very Ca + + and then a more prolonged stimulation that does not allow Ca + + pumps to expel him from the cell. The latency of 50ms and the effect can also be issued on post-synaptic neuron is much more durable. Often the action is of type neuromodulatorio, that influence the effect of the NT low molecular weight. • Removal and recovery

The NT must be continually removed from the synaptic cleft, were it not so the post-synaptic neuron could not perceive differences in the concentration of NT accumulated.
The sinks are three and act simultaneously.
L ' enzyme inactivation is the fastest and ensures that enzymes present in the synaptic cleft modifies the molecular structure of the NT or converted into more molecules. These metabolites are then summarized by the cell to create new NT.
For the catecholamines inactivating enzymes are Monomminossidasi (Mao) for the acetylcholinesterase acetelcolina which is split into acetic acid and choline. The diffusion
causes the NT escapes out of the synaptic cleft and astrocytes capture him and then return it to the neuron. The
reuptake mechanism is a pre-synaptic neuron that recognizes the NT and reabsorbed.

In many pre-synaptic neuron synapses also exist of autoreceptors who usually have inhibitory function, and modulate the release of NT in the new slot.

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Psychobiology: synapses

The synapse is the neuronal structure in which the signals are transferred from one neuron to another. The synapse consists of a pre-synaptic neuron a synaptic cleft and post-synaptic neuron . It can be as a rule, or excitatory or inhibitory , but the same neuron can receive multiple excitatory synaptic contacts is that inhibitors.
Depending on the location of synapses can be distinguished in broadcasting: ace-dendritic, axo-axonic and associated somatic .


The term pre-synaptic
In the pre-synaptic terminal contains: •
mitochondria for ATP production necessary for the synthesis of NT, enzymatic activity, transport and termination within the NT vesicles, for the Na / K and Ca
• synaptic vesicles containing NT low molecular weight.
• Active zones in which the vesicles pour the contents. •
secretory granules, not all the pre-synapse, NT peptide release high molecular weight.

Neurotransmitters
are produced by pre-synaptic neuron and to date have been identified over 70. Some are popular, others are confined to small sections of the SN.
From chemical point of view are:
- A low molecular weight amino

• Although they are ubiquitous throughout the body are not found outside the cell.
- glutamate (Glu)
Only exciter.
- glycine (Gly)
inhibitor alone.
- GABA (gamma-aminobutyric acid)
An amino acid modified inhibitor alone. Its precursor is the gluttamato.
• Amines
- acetylcholine (Ach) NT
typical of excitatory neuro-muscular junction .
is produced from the synapse and consists acetyl CoA (product of cellular respiration) and choline . The enzyme responsible for the reaction is the creation ChAT
Is inactivated by acetylcholinesterase ( AChE) which breaks down into acetic acid and choline, which is summarized by cholinergic synapses.
- Dopamine (DA)
- noradrenaline (NA)
- Adrenaline
- Serotonin (5-HT)
Dopamine, noradrenaline and adrenaline all derive from the same line metabolic and collectively are called catecholamines . The precursor of catecholamines is tyrosine , thyroid hormone, which is converted to L-dopa (missing in Parkinson's disease), the precursor of DA. The DA is the precursor of NO, which is a precursor of adrenaline.
The serotonin precursor tryptophan is . Catecholamines are inactivated the oxidase (MAO).

- High molecular weight
From 5 to a few tens of amino acids.
are released in very limited areas of the SN. • Peptides

- enkephalin (Enk)
- Somatostatin
- Neuropeptide Y
- Substance P
- etc. • Gas

Uncovered recently as NT.
- nitrogen monoxide (NO). NT

Some are exclusively excitatory (eg glutamate). Only other inhibitors (eg GABA and glycine).
Most inhibitors which can be either excitatory, depending on the type of receptor or ion channel used in the post-synaptic transmission.

Structure and ion channel subtypes
All ion channels are composed of several subunits, of which there are structural variants change the permeability, the duration of opening etc.. Of each ion channel exist in reality families of ion channels that differ in some amino acids. The M2 tract is the one that faces the pore of the channel and determines the selectivity.
In the neuromuscular junction is a cholinergic channel composed of five subunits, two of which dell'α. Each subunit is composed of four stretches of α-helix parallel through the membrane. The unit has the α active site for Ach, in this case two. In fact, the channel Ach is an exception because it requires the binding of two molecules of NT. It is not very selective in permeability cation, it passes both Na + and K +.
The ion channel is called muscle nicotinic receptor , but is found throughout the SN. It takes its name of ' agonist that increases the effectiveness dell'acitelcolina on ion channels, namely nicotine. Naturally occurring toxins in plants and animals of the nicotinic receptor antagonist, that inhibit its effectiveness, including the cobra toxin and curare. There is also a
muscarinic receptor agonist which is muscarine, but it is not an ion channel-dependent transmitter, but a G protein coupled receptor that is indirect or metabotropic . of the muscarinic antagonist atropine is, in high doses in the flowers of belladonna.
glutammaergico channel, activated by the excitatory glutamate and therefore, is divided into three subtypes based channels antagonist on AMPA , NMDA and kainate . The NMDA receptor is permeable to all cations (K +, Na + and Ca + +). It is normally blocked by Mg + + (divalent cation magnesium) that is removed when it reaches-35mV, so the transmitter is at the same time-dependent and voltage-dependent. Are always coupled to AMPA receptors and kainate receptors and provide a late component of the PPS that prolongs the effect. The permeability to Ca + + affects rather than to depolarization, the metabolic change of the neuron. In fact, play a major role in the consolidation of memory traces in neural circuits that govern memory.
Channel GABAergic, and then activated by GABA inhibitory, is divided into two subtypes GABAA and GABAB . GABA is an anion channel permeable to Cl-, but has a smaller effect of Cl-PPSE because it goes against the electrical gradient. GABAB receptor is involved in indirect synapses. GABAA alloy with a multitude of molecules agonists ( barbiturates, benzodiazepines , ethanol etc.) Other than the NT. On the other hand, each molecule is not able to open it in itself, but modifies the operation. It is composed of five subunits, but each has tens of variants, so they can get thousands of different GABAA channels.

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Psychobiology: the phases of the action potential

resting potential
the voltage-gated Na + channels and voltage-gated K + channels , concentrated in the axon mound and at the nodes of Ranvier, are closed. • Depolarization

membrane potential (Vm), did not exceed the threshold value . • The rising phase

exceeds the threshold some voltage-gated Na + channels begin to open further depolarizing the Vm. Other voltage-gated Na + channels with different sensitivity into action a chain until it reaches the potential to tip. • Potential
pointed
channels are sensitive to voltage and inactivate with a timer mechanism after about 1ms. Goes into much more than Na + and K + bait in this situation settles down in the Vm +50 mV. At this point, the threshold of action potentials, 1 ms later, the voltage-gated K + channels open. •
downturn
The cell repolarization is very fast because of concentration gradients of K + ions and electrical differences.
• Hyperpolarization
At this stage there are many channels open and K + hyperpolarized the cell and then is restored to-65mV. •
absolute refractory period
Vm returns to the rest but you can not new for less than 1 ms depolarization to a few ms.
This limits the discharge per second to about 500Hz. • Refractory Period on

At this stage some voltage-dependent Na + channels are inactive because they need a stronger than normal stimulus to trigger a new action potential. Determine a relationship between stimulation intensity and frequency of discharge. Some neurons have periods

refractory short, others have frequencies that change over time, others burst of refractory periods and longer.

conduction of action potentials in
axon mound rich in voltage-gated Na + channels, different electrical signals reach the cell and are integrated to give rise to the action potential. The signals can be excitatory or inhibitory . The first trigger the action potential.
Once unleashed begins to spread nell'assone unmyelinated, but not in elettrotonica because the cytoplasm is not a good conductor, opening voltage-dependent channels in step action potential actively. The speed is low.
Nell'assone myelinated, close to the myelin sheath, the signal can travel like a graded potential, which is a passive and almost instantaneous leakage current. The node of Ranvier, rich in voltage-gated Na + channels, riamplifica signal.

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Psychobiology: the neuron

secretory vesicles originate in the rough endoplasmic reticulum and then migrate in the appearance of the Golgi, where they mature and then migrate to their final destination. In the case of synaptic vesicles migrate to the synapse .
protein products are intended for the free ribosomes in the cytoplasm, nucleus, mitochondria and peroxisomes; those produced by ribosomes associated with rough endoplasmic reticulum are membrane proteins or secretory proteins.
The first 10 amino acids act as a signal sequence, which is then removed.
The cytoskeleton (neurofilaments ) gives shape and strength to the cell, maintains the correct position in cytoplasmic bodies, is involved in the movement of the cell plays a key role in cell division ( microfilaments). In the neuron, the cytoskeleton acts as a platform for the transport of material along the axon ( microtubules). The

axonal transport or assoplasmatico can be in three ways: •
anterograde fast (410mm/giorno) to transport organelles or vesicles from the soma to the synapse (kinesin microtubule +)
retrograde fast (200-300mm/giorno) to transport organelles or vesicles from the synapse to soma (dynein microtubule +)
axonal slow - slow component (2.5mm/giorno) - fast component (5mm/giorno) for transporting enzymes and other macromolecules
The cytoskeleton prevents the membrane proteins and membrane changes of attitude change composition of the various points of the membrane of neurons.

ion channels
important ions into the neuron for the operation are the three K + cations (potassium), Na + (sodium), Ca + + (soccer) el'anione Cl-(chlorine).
Ion channels allow ions to enter the cell and are extremely selective. The passive ion channels are open, while ion channels are open to variable access under certain conditions: 1) chemical messengers from outside the cell, and 2) responds to the second messenger produced inside the cell, and 3) according to variation of voltage between the inside and outside the cell, 4) according to the mechanical stress produced by the cytoskeleton connected to the membrane.

methods research used to study ion channels are the amino acid sequence, the map of hydrophobicity , patch-clamp analysis and immunocytochemistry .


The membrane potential
signals transmitted from the SN are made up of rapid changes in membrane potential of nerve cells.
The membrane potentials are of three types: 1) resting potential, 2) graduated potential (local potential), 3) action potential (nerve impulse or spike).
The resting potential of the neuron is-65mV and means that there are more anions inside the cell than outside. Potential graduates are
receptor or pre-synaptic and post-synaptic inhibitory and excitatory. The change in voltage is proportional to the applied current, but reaches back to the value of rest and only gradually. The change was almost simultaneously at various sites, but decreases as we moves away from the point of stimulation.

When the cell becomes less negative depolarizes, and when it becomes more negative hyperpolarized.
The action potential is reached depolarizing the cell above a threshold.


Concentration and equilibrium potential of ion homeostasis
For ions tend to focus on a uniform inside and outside the cell. The K + concentration is 20:1 in the cell phone, Na + is less concentrated in the cell, 1:10. The Cl-is concentrated outside 1:11, while the Ca + + is very rare in the cell 1:10000.
With this premise, the K + will tend to leave out hyperpolarized the cell, while the depolarizing Na + to enter.
Being electrically charged ions must be taken into account the electrical forces involved and the electrical gradient . So you can see the concentration gradient that gives against the electrical gradient. The
equilibrium potential for ion (E) is a quantity that expresses the difference of potential to have a balance between the two gradients for ion. It can be calculated using the ' Nernst equation. The K + has a cell for the EK-80 mV and the Na + +62 mV to an ENA. Why is
Vm-65mV? The cells tend to lose K + to the concentration gradient and that the cell hyperpolarized Vm bringing near EK. The extension of Nerst
equation, the ' Goldman equation, to calculate the Vm taking into account the presence of more ions.

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Psychobiology: anatomy of the central nervous system

The CNS is 1) enclosed by the bones (skull and spine) with the exception of the retina that has the same embryological origin, 2) is not washed by the blood stream, even if covered by blood vessels, the blood-brain barrier prevents the contact of blood with neurons. 3) It is enclosed by three layers of membranes called meninges so as not to impact directly the soft tissue of the CNS against the hardness of bone. Just below the bone is
dura mater that has the consistency of leather, below this the ' arachnoid and pia mater finally , soft and follows the shape of the grooves of the CNS and is fully participating. Between the pia mater el'aracnoide there is a gap that sub-arachnoid space adapting the form of two different brains. Between the dura mater is a el'aracnoideo subdural space.
Under the meninges, if you look at the brain, there is the gray matter (somata) and then the white matter (axons), conversely, in the spinal cord, there is the white matter and gray matter then .
In sub-arachnoid space containing the cerebrospinal fluid or cerebrospinal fluid (CSF) and is similar to blood plasma and the extra-cellular fluid. The LCS also fills the cavities of the CNS Call ventricles and communicates with the sub-arachnoid space. All
LCS is located inside the blood-brain barrier amounts to 125 and is fully reciprocated every 6-7 hours.


The ventricles
The ventricle is composed of two large lateral ventricles that extend the length of the brain. Communicate with the third ventricle (found in medial position), which in turn communicates through ' cerebral aqueduct with the fourth ventricle . This communicates with the spinal canal that runs through the spinal cord.
The CSF is produced by the choroid plexus the height of the ventricles and then reabsorbed by the arachnoid villi sub-arachnoid space that filters the blood. The LCS
replaces the replaces the blood within the blood-brain barrier and plays an important mechanical function, in fact, the brain floats inside the skull nell'LCS. The liquid absorbs the acceleration and reduces the overall weight from 1500g to 100g, so the base of the brain is not liable to be crushed.

The development of SN
the early stages of development, the SN is composed of a tube that grows two-dimensionally. The embryo differentiates three cell layers: ectoderm , mesoderm and endoderm which will bring different structures.
Dall'endoderma develop the internal organs and the alimentary canal; mesoderm from the bones, skeletal muscles, circulatory system and kidneys; dall'ectoderma the nervous system and skin.
Three weeks after conception the ectoderm folds on itself to form the neural groove and then closes to form the neural tube . The remaining portion of the ectoderm on the side of the tube gives rise to neural crest they carry dorsally. From
neural tube is formed by the CNS and the neural crest SNP. In the following weeks are formed from three vesicles that arise from rostral to caudal, the forebrain, the midbrain and hindbrain . The rest of the neural tube give rise to the spinal cord .
From the forebrain vesicle, which differs in telencephalon and diencephalon , will form the rostral olfactory bulbs, cerebral hemispheres the side of the forebrain, optic vesicles and . From the midbrain superior and inferior colliculi , from the hindbrain cerebellum The bridge and bulb. Optic vesicles are different from the optical stem from which derive the optic nerve and optic cup which will form the retina . Subsequently, the midbrain will differ in thalamus, the center of sensory afferents, and hypothalamus.
Up to this point, the embryo, neurons are the same as any other cell type. Soon, however, will differ in the forebrain areas occupied by gray matter and white matter (the cortical white matter the corpus callosum, the internal capsule ).
Very soon you'll see the ventricles, the two sides in the telencephalon, the third in the diencephalon, the cerebral aqueduct in the midbrain and fourth ventricle in the hindbrain.


The spinal cord is contained in the spine and begins and ends with the first cervical to the twelfth thoracic. In addition to the twelfth thoracic spinal cord continues cauda aequina .
the height of each vertebra out a pair of spinal nerves. There are three layers of meninges and the arrangement of white and gray matter is opposite to that of the brain.
The gray matter becomes an H-shaped bundles of axons and the substance white running from caudal to rostral or caudal to rostral. But the internal structure of the spinal cord varies depending on the distance of the brain, showing the height of the swelling of the limbs. There is the presence of specialized nuclei.
sensory fibers emerge dorsally in the dorsal root ganglia and dorsal root contains the soma of sensory neurons, whereas the motor fibers emerge ventrally and are called the ventral roots and somata lie within the gray matter of the spinal cord.
In the "H" of the gray matter can be distinguished dorsal horn, where do the sensory afferents, the ventral horn , home of the somata of motor neurons, and the intermediate zone where they are located for pre-ganglionic neurons of the ANS.
traits that run along the axon in the spinal white matter are called columns (dorsal column, lateral column and ventral column). Those senses are drawn upward, while the descenders are the main drivers. Ventral position in the white matter is commissure that connects the right side with the left.
The spinal nerves are divided into: cervical (8), thoracic (12), lumbar (5), sacral (5) and a coccygeal nerve .

hindbrain and midbrain
The hindbrain, distinct from the fourth ventricle, is divided into:
or bulb or medulla oblongata
is adjacent to the spinal cord and is crossed by the same bundles of axons in the spinal cord.
contains numerous nuclei involved in functions such as control of breathing, heart rate, salivation and vomiting, and cough reflexes.
is also involved in various sensory functions (hearing, touch, taste).
depart from it many of the cranial nerves.
or Cerebellum
accounts for 10% by weight of the brain, but contains 50% of all neurons.
It is involved in fine motor function and learning of new motor skills.
It is divided into two cerebellar hemispheres.
or Bridge
contains bundles of fibers that connect the two cerebellar hemispheres.
contains a structure called the reticular formation responsible for the state of general activation of the SN, such as the sleep-wake cycle.

The midbrain, which is distinct from the aqueduct of the brain, is divided into:
or
roof consists of the inferior colliculus (hearing) and superior colliculus (vision) that are also called the optical roof. The latter is particularly well developed in birds and in lower vertebrates as presiding over the most visual drawing. In humans, the visual processing is mainly performed by the cortex of the occipital lobe.
or
tegmentum contains many important structures such as the substantia nigra involved in motor control, affected by Parkinson's disease.

forebrain
The Diencephalon is located at the third ventricle and is divided into:
or Talamo
is a set of nuclei as an important processing station for all sensory information.
Various nuclei project to areas of the cerebral cortex deputies to the analysis of each sensory modality.
is involved in motor control. Emerge from the thalamus of the internal capsule fibers that link the thalamus and cortex. There is a right and left thalamus (equivalent structure).
or Hypothalamus
is located rostral to the thalamus and presides over the control of the entire organism by regulating homeostasis.
Since it depends on the temperature regulation, hunger, thirst, sleep, sleep, sexual behavior and expression of emotions such as aggression and fear. Check
activation of SNA.
Through the pituitary controls the release of Most of hormones by the various endocrine glands.

bulb, cerebellum, bridge, midbrain, thalamus and hypothalamus are the brain stem .

Telencephalon
is the most rostral portion of the brain and its development is characteristic of mammals, especially primates.
It is distinguishable from the lateral ventricles and is divided into:
or
cerebral hemispheres is the most cumbersome and consists of the brain outside the cerebral cortex , which has a thickness of 2-4 mm and is about 2000cmq (45x45cm), three times the size inside the skull. The convex part are called revolutions and troughs and furrows, the grooves are deeper fissures said.
The hemispheres are divided into lobes . The frontal lobe ventral and is bordered by the parietal lobe which is rostral. This is adjacent to the temporal lobe , caudal, dorsal and occipital lobe . The fissure of Rolando
or central sulcus separates the frontal lobe and parietal lobe. The fissure of Silvio
or lateral sulcus separates the frontal lobe from temporal lobe. The two hemispheres are separated
the fissure interemispheric .
widening the gap can be seen the lateral cortex of the insula between the temporal lobe and frontal lobe.
widening the fissure is observed interemispheric corpus callosum and the cingulate gyrus . The central sulcus separates the
precentral gyrus (frontal lobe) that is called the primary motor cortex and postcentral gyrus (parietal lobe) that primary somatosensory cortex. In the primary motor cortex and primary somatosensory cortex are ordered maps of body surface and motor homunculus homunculus somatosensory .

Brodmann in 1909 created a map cyto-architecture of the cortex, which is based on the characteristics of the tissue. Discriminated 49 different areas, is still valid and called Brodmann areas.
Areas 1,2 and 3 correspond to the primary somatosensory cortex (frontal and parietal lobe). The area 17, striate cortex, for example, is delegated the primary visual area (temporal lobe). The primary area all'uditiva 17 (temporal lobe). The fourth area is the primary motor (frontal lobe).
or Telencephalon baseline or subcortical structures
The basal ganglia are the caudate nucleus The globus pallidus and putamen involved in movement control.
L ' amygdala el' hippocampus are part of the limbic system which is involved in emotion and learning.


The blood circulation in the brain
The brain is crossed by two pairs of large arteries. The two internal carotid arteries supply blood to the rostral part of the brain, while the two vertebral arteries the caudal portion, but at deck join in ' basilar artery then divide again. The carotid arteries divide into anterior cerebral artery , which waters also the insula cortex, and middle cerebral artery . The vertebral arteries in a rteria posterior cerebral artery and superior cerebellar . Ventrally, near the optic chiasm the carotid arteries and vertebral arteries are pooled in the circle of Willis .

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Psychobiology: Psychobiology

References anatomical nervous system
nerve, tract and beam are names for groups of axons. The nerve is a grouping of the SNP, while the stretch of the CNS. A bundle is a grouping of axons that do not have the same origin and destination. In the CNS axonal group that connects the brain and brain stem is said capsule. A group that connects shares is called contralateral commissure . Traits that wind like ribbons in the brain are called lemniscate .
ganglion and generic name is to designate groups of somata. Ganglion (ganglia plur.) is a group of neuronal SNP, while the core of the CNS. There are some nuances with respect to the nucleus. If it is not very large, but separate from the rest is a locus (loci plur.). If a nucleus, however, has a not very precise boundary is called the substantia .
views of an anatomical structure can be side (right or left), dorsal, ventral , rostral or anterior caudal or later. Two structures on the same side are those ipsilateral, and contralateral on opposite sides.
sections of the structures are called median sagittal if it crosses from dorsal to ventral in rostral-caudal direction, while coronal if contralateral. One section is called horizontal if it crosses the property from rostral to caudal.

Anatomy nervous system
Structurally, the SN can be divided into two zones macroanatomiche
- SNC

• Brain • Spinal cord
- SNP
• 12 pairs of cranial nerves that leave the encephalon
• 31 pairs of spinal nerves that leave the spinal cord

SNP somatic sensory information from the sense organs
; Control voluntary muscles (motor system) •
self SNP (SNA)
control of smooth muscle (circulatory, sexual organs, digestive system etc).
- Sympathetic Activity in critical situations
and make resources available to address the emergency.
- Parasympathetic
promotes the welfare-related functions long-term needs such as energy conservation, reproduction, nutrition, immune response, digestion.
- receptors and sense organs


The spinal nerves
All spinal nerves are mixed, they are both motor neurons in the motor fibers (OUT) and sensory neurons in both sensory fibers (IN).
The motor fibers and sensory fibers from the spinal cord out independently and then meet in a single nerve.
The ventral motor fibers leave and take the name of ventral roots and sensory fibers emerge dorsally and take the name of dorsal roots, dorsal root ganglia and contain the somata of neurons, so you are out off the spinal cord .


The cranial nerves can be mixed cranial nerves (facial nerve), only sensory (Optic nerve), or just engines (oculomotor nerve).

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anatomy of the nervous system: the nervous system and cells of the nervous system

The nervous system consists of CNS central nervous system (enclosed in the bones) and the peripheral nervous system SNP. The specialized cells of the SN neurons are (100 billion) and glia or glial cells (1000-2000 billion). Makes up 5-6% of body mass but consumes 20% of energy.
neurons (10-100 μm) are responsible for electrical activity and, with certain exceptions, not mitosis. The glia are
support or electrical isolation to the neuron, are 10 times smaller and divide to life. The child at birth is less than glia to decrease the size of the skull.
Neurons are divided into three constituent parts: the soma (cell metabolism, integration of signals), the dendrites (reception) and 'axon (signal transmission). Dendrites and axons are collectively called neurites .
Dendrites (20-2000 um length), the diameter tends to shrink away from the soma. Sometimes they are provided with specializations called dendritic spines that receive the nerve impulse.
The axon, in humans, has a variable length and may exceed one meter (motoneurons foot), the diameter is between 0.2 and 20 μm and tends to remain constant. Generally part of the axon from the soma is unique, but you can branch out in axons side. The axon starts from the soma in the region called axon mound or cone emergency or cone integration and end buttons in synaptic terminals or . In its length it is covered by the myelin sheath produced by glial cells. Often the axons of many neurons run parallel and form the nerve (SNP) and tract (SNC) to gain more strength.

The classification of neurons
There are different classifications and complementary.
or size.
or function:
- sensory neurons (afferent neurons, sensory systems),
- Interneuron (system integration)
- motor neurons (efferent neuron, effector systems).
The sensory system that receives the stimulus and the effector system that produces the answer varies for different species of organisms, but the system integration is species-specific. To form or
(dendrites)
- Unipolar (sensory neurons without dendrites, eg. Somatosensory cells)
- Biploari (sensory neurons, a dendrite, for example. Cells retinal)
- Multipole (most common form, eg. spinal motor neurons, hippocampal pyramidal cells, Purkinje cells of cerebellum)
or length of the axon:
- The second type of Golgi or pyramidal cells (axon length, projection neurons)
- type II Golgi or stellate cells (short-axon, local circuit neurons) or type of neurotransmitter
:
- cholinergic neurons (acitelcolina)
- dopaminergic neurons (dopamine)
- glutamergici neurons (glutamate)
- GABAergic neurons (GABA )
- etc ...

Glial cells
- fill the space separating one neuron to another and electrically insulate axons
-
nourish neurons - Maintain a stable composition of the extra-cellular space
- led the growth in the re-growth of neuronal cells
- repair tissues and defend by pathogens (replace the immune system)

Classification:
- Microglia
They embryological origin from the mesoderm (especially macrophages).
The main function is to repair damaged tissues and engulf the dead cells.
- Macroglia
They have the same embryological origin of the neurons.
-
Astrocytes are the cells more numerous in the CNS and have a star-shaped
nourish the neuron
The CNS is not in direct contact with the blood stream even if there are large vessels passing through it.
Astrocytes levying substances from the bloodstream and nourish the neuron. Astrocytes and endothelial cells of blood vessels to form the blood-brain barrier , in fact the brain is bathed in the blood but from cerebrospinal fluid or CSF .
• Avoid the entry of virus
• Maintains constant ion concentration
• Avoid contact between molecules in the circulatory system that affect neurons
working as phagocytosis
Astrocytes can move through the pseudopodia and move en masse to the damaged area
- Capture the neurotransmitters and potassium after the exchange synaptic
- Dab the extra-cellular concentration of neurons
Astrocytes are all connected together by joints Communicating (gap junctions or tight junctions) so that their network should send the substances, when they are requested.
- They produce growth factors
are chemical molecules that indicate the direction in which the axons grow during growth or to repair damaged tissues.
-
Oligodendrocytes produce myelin sheaths in the CNS
- Schwann cells
produce myelin sheaths in the PNS

The myelin sheath
The myelin is made from 80% to 20% lipids and proteins and works as an insulator for transmission. In the PNS, the Schwann cell wraps itself around a section of the axon. In the CNS oligodenrocyte form numerous tracts of myelin on different axons. The axon is not completely covered, but there are segments of 1-2 um discovered every stroke of 1mm myelin called nodes Ravier. The
myelination begins at the 5th month of pregnancy and continues after birth than the 2nd year that at birth the newborn's brain takes 400cc in volume 1300cc instead of the average although the number of neurons is the same. After adolescence, the number of neurons begins to decrease and there are gender differences in weight for age, which is greater in the male proportion to the rest of the body.
Schwann cells act as a guide when you cut the axon, but the oligodendrocytes in the CNS axon occupy space stopped. The multiple sclerosis
is an autoimmune disease of the CNS, with incidence in the northern hemisphere, due to attack myelin from some components of the immune system can cross the blood-brain barrier. The myelin sheath produces delays missing very important areas of the brain affected.

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Applied Biology: The Science of

The sexual deformity causes males and females of the same species differ not only for the reproductive system for secondary sexual traits. In addition to physical traits you notice different behaviors. Darwin suggested that natural selection operates alongside the sexual selection.
At first glance the presence of both sexes seem disadvantageous in that: an individual would parthenogenetic offspring with 100% of its genes, and after a few generations would count more descendants.
sexed species in asexual contend that an environmental niche show that sexual reproduction with recombination allows individuals to procreate with greater genetic variation and therefore adaptability.
Reproduction assesuale is suitable for stable environmental conditions.

L ' anisogamia is the difference between male and female gametes sex. In most species the eggs are larger and a few sperm and many children.

Sexual selection favors traits in males that increase their mating success. In
intra-sexual selection favored males will be stronger in competition with other males. In
inter-sexual selection will be favored males that have characteristics favored by females.
The section that highlights the sexual selection is then balanced by natural selection, otherwise one would see a 10m high peacocks with tails or horns from deer with 100kg,

In the female sexual selection favors the selectivity , in fact a male who makes a mistake in the reproduction does not have serious consequences, a female hand, has a risk and a higher cost. The selectivity is expressed by choosing males with superior genotype, with parental skills and resources.

In humans it was found that in different cultures that attract female characteristics are inherent in the male and female physical attractiveness instead is the availability status and economic men (Buss, 1989).

A final aspect of sexual selection and sperm competition, some species have developed techniques to prevent the sperm of other males to fertilize the female arrivals who are courting.

sexual conflicts
Because dell'anisogamia and sexual selection often the interests of the two sexes are different, so that sexual selection will favor sexual traits unfavorable for the other sex. This situation triggers a sexual conflict.
A very common conflict between species is that concerning the parental care, in this case in some species the female must implement strategies to ensure that the male participants rearing of offspring without it having another female.
L ' infanticide in the lion and the mouse is a strategy that implements the new male to ensure that females stop feeding and enter into inspiration for the time domain is limited, and after winning the competition entail a risk to wait. The mouse comes to kill the male offspring born the following week. The
counterstrategies are avoid abandoning the demand for a long and persistent courtship to prevent infanticide lionesses involved in the struggles of male residents. The female mouse embryos reabsorbed into contact with the odor of new male "Bruce effect."

addition to behavioral strategies, we are witness to a chemical warfare. Some secreted substances in the ejaculate work by inhibiting the anti-aphrodisiac female libido, others act as a spermicide after mating.
in the male fruit flies produces a toxin that shortens the life of Acp female.
In our species, some compounds inhibit the immunological function in sperm female apparatus, which reduces the supply of sperm. There are of neuro-modulators, anti-aphrodisiacs.
prostate protein PSA helps move the sperm into the uterus, but also causes prostate cancer. The incidence of this is 60 years.

In some species, males have to endure. In the case of the female mantis, and some spiders, bigger, devouring the male just after fertilization. We are witnessing infidelity in monogamous pair of certain birds, then the token male, the female for days required for egg laying ( mate guarding ) In other bird species only one parent is sufficient that the female attempts to cheat male on the fact that he laid in his nest, but if the male finds the female rimmarrà to care for the eggs, otherwise it belongs to my son.

Occasionally males devote themselves in a sexual obsession ( sexual harassment) that in many cases leads the female to give up to reduce costs.

Altruism and Cooperation
Topics include overall fitness and kin selection, reciprocal altruism and cooperation.

Altruism: an individual behavior that increases the fitness of others at the expense of their own.
Altruism is apparently in contradiction with the theory of natural selection, but is explained if we introduce the concept of total fitness which is the sum of its fitness (direct fitness) and fitness indirect (genes shared by relatives) , Hamilton (1964).

The mechanism that allows the evolution of altruistic behavior is the kin selection (kin selection ), Hamilton has shown that the condition for which an altruistic allele is inherited is explained by the inequality:
C \u0026lt;B * r => Cost \u0026lt;Benefit * The coefficient of kinship

kin recognition is the recognition of individual indiviui related. The easiest answer to the rule "if it is grown in your own nest then it is your brother." Another mechanism underlying the kin recognition is the phenotypic comparison, for example, by comparing their major histocompatibility complex (MHC), which is expressed by the smell, with another individual. Humans are recognized physical traits, eg. DeBruin (2005) in an experiment the participants must choose between 3 faces who was reliable and more attractive in a casual relationship: the faces most similar to the participant were considered reliable and the other attractants.

L ' reciprocal altruism and cooperation to carry out altruistic behavior predict that individuals are not related. In co-operation is a temporary behavior of altruism to get more benefits, mutual nell'altruismo expects the altruistic behavior is reciprocated at a later time.

reciprocal altruism is a risk for because DETECTION can not be returned.
Trivers (1971) points out the rules for success in this case reciprocal altruism:
1) the benefit to the recipient must be greater than those who do
2) the assistants should be social, live long and permanent residence , and then have the opportunity to meet again several times
3) must be able to recognize, therefore, have evolved a cognitive system

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sexual selection: natural selection

At 800 the idea that species evolve over time with new appearances and extinctions was accepted at an academic level. The evidence for evolution were already known to biologists before Darwin. For example, for the comparative biology wing of the bat, the fin whale and the man's arm has the same structure in common (homologous) because they are derived from the limb of the mammalian quadrupeds. Embryology is known that the early stages of embryonic development are almost identical in many different vertebrate species. Paleontology know what species of animals existing in geological time was far from our diverse and in some cases it is possible to reconstruct the transition.
A half of the 800 did not know the mechanism by which this could happen. In 1859 Charles Darwin published Origin of Species and gave answers on the mechanism of natural selection . The idea of \u200b\u200bDarwin
begins by noting the way in which farmers get different breeds through artificial selection. Farmers select individuals with a salient feature, and if this is hereditary is the next generation. From 1831 to 1836 Darwin traveled around the world on HMS Beagle and experience behind the understanding of natural selection was the observation of adaptation and speciation occurred from the Galapagos finches.
A source from another discipline, economics, came from Thomas Malthus by the Essay on Population who had pointed out how the animal and human populations tend to grow if not limited, tending to occupy geometrically all the space available, the availability of limited resources, the competition among individuals, predation and the spread of disease limit the maximum number of individuals.
in natural selection there is the overproduction : Each species produces more individuals than they reach maturity; limits to growth: each population is limited in number due to limitations of space, food resources, causing a proportion most individuals do not reach maturity and reproduction; variability : individuals show differences, some of these hereditary success ripprodduttivo differential : if a feature allows a greater survival you play more, with the passing of generations, is spreading in the population.
The Natural Selection produces adaptation to the environment. A case of adaptation observed in the act is relative to industrial melanism : butterflies with alleles for the color of light and dark wings with allele survived more clear when the birch trees were clear, here in the dark of the trunk because of the English industrial revolution the trend is opposite. Another form is the act antibiotic resistance in bacteria : resistant bacteria have a chance to reproduce.


Micro and macroevolution At the time of Darwin
dell'eridatarietà mechanisms were not known because the theory of natural selection could not be formalized. Between the wars biologists incorporate population genetics was born in Darwin's theory and the synthetic theory of evolution . In the theory of individual variability arises by mutation and evolution is seen mainly as changes in allele frequencies.
Changes in allelic frequencies in generations is defined microevolution, but can not explain the huge differnza between species this requires other mechanisms.

The principle of Hardy-Weinberg describes the relationship between allyl frequencies and the frequencies of different genotypes for a particular gene. Allows geneticists to determine the frequency of each allele frequencies starting from different genotypes or vice versa, starting from the relative frequency of alleles of a gene in the ideal population. In the ideal population distribution of alleles remains constant. Alter the balance of the Hardy-Weinberg involved 1) the natural selection, 2) the mutation , 3) the gene is derived , 4) the non-random mating , 5) the gene flow .

The mutation is based on which natural selection acts and a significant accumulation of changes affect the balance Hardy-Weinberg.
not random couplings are determined by the proximity of kin, and whether the possibility of incest is avoided (as in mammals), we have an inbreeding. In some species there is a prevalence of assorted mating in which individuals choose partners based on their similarity to the phenotype.
Hardy-Weinberg's law is valid if the population is large to enforce the laws of probability, but people with a few specimens you have the gene for which is derived alleles can be eliminated in generations.
The bottleneck effect is when people become too few and we are witnessing the impoverishment of the gene pool. A special case is
the 'founder effect for which individuals from a larger population colonizes an isolated their gene pool is the only one available.
Gene flow occurs when a population welcomes people from migration by increasing the gene pool. In contrast to the drift and nonrandom mating gene flow increases genetic variability.

Natural selection can be of three types: 1) directional , 2) stabilizing , 3) diversifying . In
stabilizing selection will favor a particular value of a character's extreme detriment. In
directional selection favors one extreme disadvantage is the opposite and the intermediate
In diversifying selection will favor the extreme disadvantage and the intermediate (rare).

Natural selection usually tends to reduce the genetic variability by eliminating characters that do not fit the environment, but in other cases, natural selection may favor the same variable if 1) varies in space and time, when there are 2 ) if there is balanced polymorphism and 3) frequency-dependent selection. The

spatial and temporal variations in natural selection is to favor individuals with different phenotypes depending on where you are (presence or absence of predators) or time (or cold months the warmer months). In skinned human species phenotypes are favored in areas with little sun and dark skin in the area with plenty of sun increasing the variability in the total pool of the human species. The

balanced polymorphism is the preference in some circles to heterozygous individuals, who have that dominant and recessive alleles for the same character. For example, sickle cell anemia. The

frequency dependent selection is a mechanism that favors the individual with the rare phenotype. In some species, including humans, females may prefer dissimilar inbred individuals.

Speciation and extinction
Alone specified processes do not explain the enormous variety of species.

For ' extinction is known that changes in physical conditions (eg weather), parasitic infection, predation, competition won by antagonistic species that makes better use of the ecological niche may be a disappearing species.

For speciation is necessary 1) to form a reproductive barrier between populations, 2) there are distinct ecological niches and different selective pressures. The

speciations are 3 types: 1) allopatric , 2) parapatrica , 3) sympatric . In allopatric speciation
the population is divided into populations isolated geographically, over time these differences will accumulate isolated groups can no longer reproduce with the population base. In parapatrica
speciation, even without barriers, extending the territory included several ecological niches causes the population fits into an ecosystem.
In sympatric speciation occurs when a genetic event in a population so that individuals do differ. Some mature individuals of substantial difference in favor of the habitat and reproduction will be favored with like-minded individuals. So barriers are formed and prezigotiche postzigotiche (economically disadvantaged).
prezigotiche Among the barriers can be a temporal isolation or behavioral. Among the barriers
postzigotiche the individual can manifest sterility or is poorly adapted to the habitat.

Sexual preferences based on the histocompatibility genes
The major histocompatibility complex or MHC is composed of many genes and is implicated in the response immunitraria against non-self, eg. causes the rejection of transplants. Many animals, including humans, recognize different MHC on the basis of smell. In our case this process is completely unconscious, but it can be demonstrated experimentally.
In choosing the male for breeding females based their choice on similarity of MHC.
man the time of ovulation in female prefer individuals with different MHC from their offspring to have greater variability in gene expression, on the other days of the cycle prefer people with similar genes.

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applied biology: from Mendel to modern genetics

Gregor Mendel conducted his experiments between 1850 and 1865. It was felt that the characters were transmitted to offspring and which mix in the child. Mendel disproved the second belief but served 40 years before his work was included.
The success of Mendel's research is due to a rigorous experimental design and use of the laws of probability.
The choice of study organism was assigned to the sweet pea : has a numerous progeny, it is easy to manipulate reproduction in that it can be pollinated or self-pollinated; 7 characters had chosen a complete dominance and were eriditati independently of each other. A
character is a feature observable body, once the form in which it occurs.
L ' intersection is severing the anthers to prevent self-pollination, and carrying pollen from one plant to another. Mendel had available lines of well, that self-pollinated gave the same character.
crossing two inbred lines (g enero parental P) with the opposite character traits and get a first filial generation F1 . In this there was a mixture, but a single stroke. He discovers that a trait is dominant and a recessive ( principle of dominance). In self-pollinated F2 generation produced by the stroke recurrence. To explain this
Mendel realized that both sections were left in the offspring, in terms of genotype traits are defined alleles. So if an individual has two alleles for different traits in the phenotype will manifest the dominant one. An individual is said
homozygous, homozygous recessive if the alleles are recessive or dominant and homozygous dominant if it has identical alleles for the character, and heterozygous if different alleles.

The first law Mendel's law of segregation that character said that during gamete formation the two alleles segregate (separate) ending on different gametes.
We now know that there are two alleles of its chromosomes and that the segregrazione of alleles occurs during meiosis.

Mendel used the square Punett to determine the amount of transmitted alleles, but could not understand what were the presence of heterozygotes, because the phenotype was identical. The only way that allowed him to understand was a cross check with the homozygous recessive ( dihybrid cross).

The second law of Mendel is used to refer to the way in which alleles of different traits assort is at crossroads: the
law independent assortment says that the alleles belonging to different genes segregate independently at the time of gamete formation and are inherited independently of each other.
But today we know that is not universally true, in fact when the genes controlling two characters are close in the same gene tend to be associated with offspring. A

allele is a sequence of a gene. Different alleles for a gene exist because are subject to mutations, a rare and random process that changes the genetic material. Geneticists call a wild-type gene if the allele is present in nature in most individuals.
dominance is not always complete because some genes are subject to multiple alleles (more than two alleles).
When a heterozygous subjects manifested an intermediate phenotype with respect to the generation partentale is said that the gene is subject to incomplete dominance. In some cases both alleles are dominant and you have the codomain (such as blood group AB).
Other alleles have multiple phenotypic effects and is called pleiotropic .

How genes interact?
A gene locus is the position of a gene on chromosome and is called polymorphic if it might present a mutant gene.
L ' epistasis is the influence of genes in phenotypic expression. In some phenotypic expression (height, skin color) the character is polygenic , ie more different genes work together to the final result. The genes associated

reside in the same chromosome and tend to be distributed contemporanenamente, with the exception of crossing over, recording the second law of Mendel, since the characters observed were located on different chromosomes. Probabilitàù with which the two genes on the same chromosome recombine is linked to their distance if they are close is low, if they will almost certainly far.

The laws of genetics and post-mendialiana medeliana can be used to predict the transmission of genetic diseases humans. The majority of genetic diseases are caused by a recessive allele. Generally
genetic diseases are due to defective production of an enzyme that cuts the pathway, but in the case of the heterozygous dominant allele can compensate.
A protein enzyme can easily be mutations that affect its overall performance, if the position is wrong or the amino acid has a charge different from the above we can create damage prevented the allosteric binding of the substrate with the active site. Genetic diseases
autosomal recessive: Cystic fibrosis, phenylketonuria, certain forms of diabetes, galactosemia. Generally
disease caused by a dominant allele from the population are removed quickly if the individual is unable to reproduce. Huntington's disease (HD) is a progressive neurodegenerative disease that takes over after 30 years in adulthood and results in dementia, unfortunately the progeny carrying a sick 50% of alleles.
Other genetic diseases are autosomal dominant achondroplasia dwarfism, polydactyly, neurofibtomatosi, galucoma chronic.
sickle cell anemia individuals heterozygous both red blood cells because the allele is codominant.
This mutation has survived because the sickled red blood cells resistant to infection of malaria. The cost is that an individual's offspring out of 4 present the homozygosity for allele and sickle cell anemia soppravviverà. 44/46

human chromosomes are the autosomes, that contain the same sequence of genes, but not exact sequence of DNA that can carry different alleles.
The remaining two are sex chromosomes or eterocromosomi . and are designated with X and Y, in the portion you are not homologous genes that allow sexual differentiation.
humans XX is an individual female (sex omogametico), and XY is a male (sex eterogametico ).
The female gametes are always X and X and Y sperm can be and have a different strength.
Some genes that are in non-homologous portion of the X chromosome, which therefore has no counterpart in Y, given the effects in males who do not have a dominant allele. Color blindness, hemophilia and are predominantly male disease produced dall'eterocromosoma maternal X. Mutations can be

gene or chromosome . The genetic mutation or
point are due to the substitution, deletion, insertion of nucleotide bases in DNA.
gene mutations caused by substitutions produce altered proteins and the consequences are of 3 types:
- silent mutation → relate to third base codon of mRNA that is often irrelevant to the amino acid.
- → a missense mutation of codon base alters the encoded amino acid (the genetic variation on which natural selection works).
- nonsense mutation → codon represents one amino acid instead of the start codon or stop, or vice versa.

In all deletion and insertion of the genetic code is translated and then following completely altered. Could be due to an error in DNA replication or physical agents (X or UV) or chemical mutagens.

mutations in the structure of chromosomes 4:
- → deletion of part of chromosome is lost (syndrome du cri du chat).
- → duplicating the chromosome is duplicated in the regulation of causing damage.
- → reversal after a break in the chromosome is assembled in an inverted position, gives no serious consequences except that we will be crossing over.
- → translocation following a break off a part of the chromosome and is inserted in a different chromosome, rendondo complicated pairing during meiosis.

The mutation of chromosome number (aneuploidy ) if, during meiosis a pair of chromosomes does not separate (nondisjunction) we have a cell with one chromosome less ( monosomy) and one with an extra chromosome ( trisomy ). No monosomy allows the development of the embryo, while trisomy of chromosome 21, it has Down syndrome. Aneuploidy affects 2 / 10 pregnancies. Down syndrome 1 / 700 and the age of the mother is directly proportional to the probability of the birth of a Down child. Aneuploidy
eterocromosomi causes less disturbance to the balance gene: X0 Turner syndrome, metafemmina XXX, XXY Klinefelter syndrome, XYY male normal.

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applied biology: cell cycle

For a cell to divide requires 4 events:
- signal reproductive
internal or external - DNA replication
- segregation → duplicated DNA is divided into daughter cells
- cytokinesis → daughter cells are separated

I prokaryotes divide to division, environmental conditions determine the rate of reproduction and the playing time. In DNA replication, usually contained in a single chromosome in circular form, are important regions gold (the origin of replication) and b (end of replication). The DNA is replicated at the center of the cell and then the gold regions at the poles move with increasing the plasma membrane. The cytokinesis begins with a constriction of the plasma membrane with a ring, is synthesized new cell wall material. The

eukaryotes divide to mitosis or meiosis (only gametes). Eukaryotic cells do not divide continuously or for environmental condition and contain more chromosomes and organelles in the cytoplasm.
The set of events that make up life is said eukaryotic cell cycle. Macrophases are 2: interphase and mitosis (M). The interphase consists of three phases: stability phone (G1), DNA synthesis (S) and period between synthesis and division (G2).
The enzyme that causes the shift in M \u200b\u200bis said cyclin-dependent kinase or Cdk activated by a cyclin. The cell proceeds with duplication once passed the restriction point in G1 R . retinoblastoma protein (RB) inhibits the cycle, but if there shall be phosphorylated S. During the duplication

chromatin condenses to form chromosomes once duplicates are two sister chromatids together in a centromere protein that coesina and coated condense.
Chromatin is the DNA sequence folded into nucleosomes, ie 4 pairs of DNA wrapped around histones and locked from the outside ' histone H1.
During DNA replication the centrosomes (centrioles pairs, starting points of the microtubules) reach the opposite poles of the nucleus.
The 6 phases of mitosis are: prophase in chromatids are still united and formed the kinetochores, the sites where the chromatids are attached to the spindle (web of microtubules). In prometaphase lìinvolucro nuclear dissolves and is attached to the spindle. In the metaphase chromatids are divided into chromosomes and are arranged in equatorial plate the nucleus. In ' anaphase the daughter chromosomes move to opposite poles, and then in the telophase chromatin despiralizza, nuclei are formed and begin cytokinesis.
In cytokinesis the actin and myosin form a contractile ring that separates the cytoplasm, the organelles are separated inside. The

mitosis can be repeated indefinite times, while meiosis results in only 4 daughter cells.
Meiosis is used to produce a gamete that contains a karyotype half (haploid ) compared to the cell zygote . The zygote is the union of two gametes with two different chromosome pairs (diploid ).

During meiosis the nucelo divides twice, but the DNA is duplicated only once. The first meiotic division (meiosis I ) halves the number of chromosomes and the chromosomes migrate to the poles of the cell. In prophase I , the chromosomes (that year, the same genes) are displayed along the major axis. The adjacent chromatids form a chiasm that allows you to exchange genetic material from one chromatid to another ( crossing over). This further increases the genetic variability and allows an individual to be able to transmit genes that may be two different chromosomes.
At the end of meiosis II means 4 daughter cells stateless.

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Biology applied: the cell membrane

The structure of biological membrane is known as fluid mosaic, the walls are made of phospholipid bilayer . The polar heads (phosphate groups) are hydrophilic and streams are at the ends, while the polar tails (fatty acids) hydrophobic are inside.
The fluidity is given by the lipid composition (length of chain fatty acids, saturation, polarity given by the phosphate groups) and the temperature.
A number between 0 and 20% is made up of cholesterol that prevents stiffening of the membrane at low temperatures and become too fluid to high temperatures.

The average density of protein is 1 to 25 phospholipid molecules and are divided into two types:
- the whole protein penetrate through the wall of phospholipid, those that cross completely are called transmembrane proteins.
- the peripheral proteins that are not immersed in the bilayer.
Some proteins are not free to move and are anchored by the cytoskeleton or lipid floating semi-fluid.

Phospholipids are synthesized in the endoplasmic reticulum proteins in smooth and rough endoplasmic reticulum.

Carbohydrates are located at the outer ends of the transmembrane protein and have the function of recognition sites and signaling. and glycolipids are glycoproteins.

membranes allow only be crossed by some substances, selective permeability. There are two ways for the transport of substances passive, requiring no additional energy, and active , requires ATP.
The case for passive diffusion that can be easily or facilitated.
Diffusion is the process by which a solution reaches an equilibrium state where there is a net movement of particles between a high concentration to a low concentration,
The diffusion rate is a function of diameter of the molecules, the temperature of the solution, the electric charge and concentration gradient is the change in concentration between different points. One solution may be isotonic , hypotonic or hypertonic of the comparison of solute relative to another.
more a molecule is soluble, therefore hydrophobic, so it penetrates more easily through the membrane.

If the substance is not soluble it passes through the membrane by the concentration gradient through specific proteins (facilitated diffusion). There
channel proteins, such as ion channels that allow the selective passage of one type of ion, and carrier proteins that help the transition of complex molecules.
Ion channels are central to every activity of the nervous system and can be adjusted (ie variable-access) from messengers intra / extracellular changes in electrical or mechanical stimuli.

The transport of substances against the concentration gradient occurs through carrier proteins that require ATP and each is specialized for one type of substance. They are divided into Uniport (one molecule each way), simporto (more molecules each way) and Antiporto (more molecules different directions). A carrier is very important Antiporto sodium-potassium pump, which puts two K + ions in and out 3 Na + ions with the result that the concentration of these is very different between the inside and outside the cell.

L ' endocytosis is the way that the cell has to introduce large molecules el' Exocytosis is the reverse process. Endocytosis can
be phagocytosis (ingestion of solids), pinocytosis (fluid intake) and receptor-mediated endocytosis or uptake.
Some proteins (eg clathrin) coat the exterior portions of specialized plasma membrane called coated pits the pit invaginates and forms a vesicle .

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applied biology: the eukaryotic genome and its expression

The eukaryotic genome is larger than the prokaryotic, owns more regulatory unit, much of the DNA does not encode proteins, eukaryotes have multiple chromosomes , transcription and translation processes are separated. The

eukaryotic genome is repetitive and were indivuidati varying degrees of repetition:
- highly repetitive sequences are not transcribed, we do not know the role
- 10-40 bp minisatellites x 10 ^ 3 times
- microsatellite bp 1-3 x 10 ^ 1 translated into protein, 17% gu
- retrotransposons, make a copy themselves into RNA, 8% gu
- DNA transposons move independently within the genome.
Their movement can produce major consequences if it is placed in the coding gene contribute to the variability. eukaryotic genes contain non-coding sequences may be raggurappati in families.
addition to the promoter in the coding part is comprised of a
terminator, which is a sequence after the stop codon, end of ribosomal translation, that communicates the end of the RNA polymerase transcription. Inside the coding is introns are parts which are not translated, and
exons that are translated. The introns are removed from the pre-mRNA and the exons are joined. This process is called splicing
, it is possible that the same pre-mRNA can be created with different types of mRNA alternative splicing

. In the nucleus

pre-mRNA assume the ends of the molecules that ensure stability, the 5 'cap is added G and 3' poly A tail of a . Between exons and introns are sequences of consensus that the molecules bind snRNP, small ribonucleic acid particles. A complex RNA and protein spliceosome said, cutting the extremities of the introns and joins exons.

There are post-transcriptional regulation and transcription. The project promoter sequences are more variable than prokaryotic genes and may contain information relating to their own rate of transcription. Unlike prokaryotes, eukaryotes need transcription factors to trigger the RNA polymerase transcription, the TATA box , the start of promoter has a transcription complex assembly of various proteins, of which the is the first transcription factor TFIID . much further, even 20,000 bp, we find
amplicons, which bind activator protein

. There are also silencers, DNA sequences that arrest transcription and bind to proteins called repressors . Another technique is the change in chromatin structure (chromatin remodeling

) chromosome, which contains not only DNA but also proteins called histones , which collect in the chromatin nucleosomes . Certain enzymes can change the links of nucleosomes, releasing the DNA so that the transcription complex can carry out the transcription. Another technique is the ' gene amplification, which consists of reproduction of the same gene in the genome several times.

The stability of mRNA can be regulated with a review of the pre-mRNA with the insertion or alteration of nucleotides. A molecule is very unstable in the cytoplasm and undergoes faster than the complex of ribonuclease esosoma. Micro RNA can bind the mRNA invalidating the translation. adjustment lifespan of a protein within the cell through the insertion of functional groups that serve as markers

for an enzyme binds to the protein ' ubiquitin which will then be recognized by a proteasome

that hydrolyze the protein.

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