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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