Question

Identify the role of the sarcolemma, t-tubule system and sarcoplasmic reticulum in excitation-contraction coupling

A) Sarcolemma conducts action potentials, leading to calcium release from the sarcoplasmic reticulum
B) T-tubules store calcium ions for muscle contraction
C) Sarcoplasmic reticulum generates action potentials for muscle excitation
D) Sarcolemma releases calcium, triggering muscle relaxation

Answer 1

The sarcolemma conducts action potentials, the T-tubule system transmits these signals into the muscle fiber, and the sarcoplasmic reticulum releases calcium ions in response, initiating muscle contraction.

Step-by-step explanation:

The role of structures in excitation-contraction coupling involves several key processes and components:

• The sarcolemma conducts action potentials that lead to the excitation of the muscle fiber.
• The T-tubule system allows the action potential to travel deep into the muscle fiber, ensuring the signal reaches the sarcoplasmic reticulum (SR).
• The sarcoplasmic reticulum (SR) stores calcium ions (Ca2+) and releases them in response to the action potential, initiating muscle contraction.

Sequence of Events:

1. Acetylcholine released from a motor neuron binds to receptors on the sarcolemma.
2. An action potential arises and travels along the sarcolemma and down the T-tubules.
3. The action potential triggers the release of Ca2+ from the SR into the sarcoplasm.
4. The influx of Ca2+ into the sarcoplasm initiates interaction between actin and myosin filaments, leading to muscle contraction.

Thus, option A is the correct role description: The sarcolemma conducts action potentials, leading to calcium release from the sarcoplasmic reticulum.