Question

Which of the following can trigger a muscle twitch?

A. Release of acetylcholine
B. Release of calcium from the sarcolemma
C. Electrical stimulation
D. Release of acetylcholine or electrical stimulation
E. Release of acetylcholine or release of calcium from the sarcolemma

Answer 1

Muscle twitches can be triggered by the release of acetylcholine at the neuromuscular junction or by direct electrical stimulation, leading to an action potential that releases calcium ions from the sarcoplasmic reticulum and results in muscle contraction.

Step-by-step explanation:

Triggers for a muscle twitch can include either the release of the neurotransmitter acetylcholine (ACh) or electrical stimulation. When a nerve impulse reaches the neuromuscular junction, it causes the release of ACh from the axon terminal into the synaptic cleft. ACh then binds to receptors on the sarcolemma of the muscle fiber which depolarizes the membrane and generates an action potential.

This action potential travels along the sarcolemma, down the T-tubules, and triggers the release of calcium ions (Ca2+) from the sarcoplasmic reticulum (SR). The calcium ions bind to troponin on the actin filaments, leading to muscular contraction. Therefore, both release of acetylcholine and electrical stimulation are correct answers as either can trigger a muscle twitch.

Answer 2

Muscle contraction can be triggered by the release of acetylcholine or electrical stimulation.

Step-by-step explanation:

Muscle contraction is triggered by the release of acetylcholine (ACh) or electrical stimulation. ACh is the neurotransmitter that binds at the neuromuscular junction (NMJ) to trigger depolarization, leading to the propagation of an action potential along the sarcolemma. On the other hand, electrical stimulation directly excites the muscle fibers, causing them to contract.