MEDICAL PHYSIOLOGY

Detailed explanation-1: -Muscle contraction is controlled by receptors in the muscle cell membranes that respond to the neurotransmitter acetylcholine when it is released from motor neurons. Acetylcholine receptors are also found on neurons, where they perform a variety of important functions, including modulating cognition and addiction.

Detailed explanation-2: -Acetylcholine is the neurotransmitter at neuromuscular junctions, at synapses in the ganglia of the visceral motor system, and at a variety of sites within the central nervous system.

Detailed explanation-3: -However, through the nicotinic cholinergic receptors, acetylcholine allows for skeletal muscle contraction; in the adrenal glands, the release of adrenaline and norepinephrine; and in the peripheral sympathetic ganglia, activation of the sympathetic system with the release of norepinephrine.

Detailed explanation-4: -Acetylcholine is the chief neurotransmitter of the parasympathetic nervous system, the part of the autonomic nervous system (a branch of the peripheral nervous system) that contracts smooth muscles, dilates blood vessels, increases bodily secretions, and slows heart rate.

Detailed explanation-5: -When acetylcholine binds to acetylcholine receptors on skeletal muscle fibers, it opens ligand gated sodium channels in the cell membrane. Sodium ions then enter the muscle cell, stimulating muscle contraction.