MUSCLE PHYSIOLOGY

Detailed explanation-1: -Neurotransmitter release occurs when an action potential travels down the motor neuron’s axon, resulting in altered permeability of the synaptic terminal membrane and an influx of calcium.

Detailed explanation-2: -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-3: -Calcium triggers contraction by reaction with regulatory proteins that in the absence of calcium prevent interaction of actin and myosin.

Detailed explanation-4: -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-5: -Muscle contraction is known to be regulated by calcium. An action potential generated by a motor neuron propagates on the muscle cell surface, activates voltage-gated calcium channels and allows calcium flow into the muscle cell.