Question

The action potential that triggers a muscle contraction, travels deep within the muscle cell using:
A) Sarcoplasmic reticulum
B) Transverse tubules
C) Synapse
D) Motor end plates

Answer 1

Hint:
The cell membrane of the muscle fiber is called sarcolemma and sarcoplasm contains fine thread-like contractile structures called myofibrils. The signal for muscle contraction comes from the nerve by triggering an action potential in the sarcolemma.

Complete step by step answer:
Action potential from sarcolemma then propagates through the T-tubules(transverse tubules). The t-tubule membrane contains voltage-sensitive proteins, which are activated by the incoming action potential.
An increase in cytoplasmic calcium initiates the contraction of each myofibril. The increase in calcium concentration is transient because calcium is rapidly pumped back into the sarcoplasmic reticulum by an abundant, calcium ATPase, in its membrane. Typically, the cytoplasmic calcium concentration is restored to resting levels within 30 milliseconds, allowing the myofibrils to relax.
The sarcoplasmic reticulum has the intracellular calcium stored in striated muscle and regulates excitation-contraction coupling and intracellular calcium concentrations during contractions and relaxation. So it is the regulator of calcium ions storage and releasing homeostasis during the process of muscle contraction.

Option ‘B’ is correct

Note:
A chemical synapse that is formed at sites where the terminal branches of the axon contact a target muscle is known as a motor end plate. It releases acetylcholine from presynaptic neurons into the synaptic cleft that activates nicotinic receptors on the motor end plate. And synapse is the point of contact from where information is passed from one neuron to another.