Question

what is the basic unit of muscle contraction in skeletal and cardiac muscles?
a.) sarcoplasmic reticulum
b.) myofibril
c.) sarcomere
d.) myofilament

Explanation:

• Sarcoplasmic reticulum: Stores and releases calcium ions but is not the basic unit of contraction.
• Myofibril: Composed of sarcomeres; it is not the basic unit itself.
• Sarcomere: The fundamental repeating unit in muscle fibers (in skeletal and cardiac muscles) responsible for contraction as actin and myosin filaments within it interact.
• Myofilament: Includes actin and myosin filaments which are part of a sarcomere.

Answer:

C. Sarcomere