Question

69.Neurotransmitters. Acetylcholine and peptides: biological role and mechanisms of

action.

(please more explanatıon Im medicine student) thank you...

Answer 1

Ans . Neurotransmitters :- These are endogenous chemicals acting as signaling molecules that enable neurotransmission. They are a type of chemical messenger which transmits signals across a chemical synapse from one neuron ( nerve cell) to another ' target ' neuron , to a muscle cell , or to a gland cell.

Neurotransmitters are released from synaptic vesicles in synapses into the synaptic cleft , where they are received by neurotransmitters receptor on target cell.

Neurotransmitters are essential to the function of complex neural systems.

1) Acetylcholine :- It is the neurotransmitter used at the neuromuscular junction . It is the chemical that motor neurons of nervous system release in order to activate muscles . Acetylcholine is the primary neurotransmitter of the parasympathetic nervous system.

Acetylcholine causes muscles to contract, activates pain responses and regulates endocrine and REM sleep functions.

Acetylcholine exerts its effects by binding to and activating receptors located on the surface of cells. There are two main classes of acetylcholine receptor, nicotinic and muscarinic.

(i) Nicotinic acetylcholine receptors:- These are ligand-gated ion channels permeable to sodium , potassium and calcium ions. These ion channels are embedded in cell membranes , capable of switching from a closed to open state when acetylcholine binds to them ; in the open state they allow ioons to pass through.

(ii) Muscarinic acetylcholine receptors :- These receptors have a more complex mechanism , and affect target cells over a longer time frame . In mammals, 5 subtypes of muscarinic receptors have been identified., labelled M1 through M5. All of them function as G protein- coupled receptors, meaning that they exert their effect via a second messenger system.

2) Oxytocin is a peptide hormone and neuropeptide . It is normally produced in the hypothalamus and released by posterior pituitary.It plays a role in social bonding , sexual reproduction, childbirth, and the period after childbirth. Oxytocin is released into the bloodstream as a hormone in response to stretching of the cervix and uterus during labor and with stimulation of nipples from breastfeeding.This helps with birth, bonding with baby and milk production.

3) Somatostatin , also known as growth hormone- inhibiting hormone , is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein- coupled somatostatin receptors and inhibition of release of numerous secondary hormones. Somatostatin inhibits insulin and glucagon secretion.