MUSCLE PHYSIOLOGY

Detailed explanation-1: -Skeletal muscle contraction and changes with exercise. (A) Neurotransmitter (acetylcholine, ACh) released from nerve endings binds to receptors (AChRs) on the muscle surface. The ensuing depolarization causes sodium channels to open, which elicits an action potential that propagates along the cell.

Detailed explanation-2: -When a neurotransmitter binds to its receptor on a receiving cell, it causes ion channels to open or close. This can produce a localized change in the membrane potential-voltage across the membrane-of the receiving cell. In some cases, the change makes the target cell more likely to fire its own action potential.

Detailed explanation-3: -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-4: -The sodium influx also sends a message within the muscle fiber to trigger the release of stored calcium ions. The calcium ions diffuse into the muscle fiber. The relationship between the chains of proteins within the muscle cells changes, leading to the contraction.

Detailed explanation-5: -The acetylcholine binds to the nicotinic receptors concentrated on the motor end plate, a specialized area of the muscle fibre’s post-synaptic membrane. This binding causes the nicotinic receptor channels to open and let sodium ions enter the muscle fibre.