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: -Skeletal muscle contraction begins first at the neuromuscular junction, which is the synapse between a motoneuron and a muscle fiber. Propagation of action potentials to the motoneuron and subsequent depolarization results in the opening of voltage-gated calcium (Ca2+) channels of the presynaptic membrane.

Detailed explanation-3: -Alpha motor neurons (also called lower motor neurons) innervate skeletal muscle and cause the muscle contractions that generate movement.

Detailed explanation-4: -Muscle contraction is initiated with the depolarization of the sarcolemma caused by the sodium ions’ entrance through the sodium channels associated with the ACh receptors. Figure 15.4. 2: This diagram represents the sequence of events that occurs when a motor neuron stimulates a muscle fiber to contract.

Detailed explanation-5: -Context: Mechanism of Skeletal Muscle Contraction The axon terminals contain vesicles containing the neurotransmitter acetylcholine (ACh), which when released, acts on the plasma membrane of muscle fibers, starting a cascade of reactions that ultimately lead to the contraction of muscles.