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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