1a Explain how muscle cells are stimulated to contract event

1a- Explain how muscle cells are stimulated to contract. (events at NMJ muscle impulse/AP) and (b) Define motor unit recruitment and explain how it leads to an increase in force.

Solution

a. A motor neuron stimulates a muscle fiber by firing a nerve impulse, which causes the muscle fiber to contract. Myofibrils or muscle fibers which are basic units for muscles directly connected to the motor neurons. The neuromuscular junction, also known as the synapse, is the intersection between a motor neuron and a muscle fiber. When a motor neuron transmits a nerve impulse to the synapse, the neurotransmitter acetylcholine is produced. This triggers an action potential that stimulates the myofibrils, which in turn cause the muscle fibers to contract.

b. A motor unit consists of a motor neuron, a skeletal muscle fibers innervated by that motor neuron\'s axonal terminals. Groups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units within a muscle are considered a motor pool. Motor unit perform a special function called Motor Unit Recruitment to increase the force. Motor unit recruitment refers to the activation of additional motor units to accomplish an increase in contractile strength in a muscle.