Question

question 21 arrange these structures as they participate in excitation - contraction. t tubules, sarcolemma, ca²⁺, sarcoplasmic reticulum ca²⁺, t tubules, sarcolemma, sarcoplasmic reticulum sarcolemma, t tubules, sarcoplasmic reticulum, ca²⁺ sarcoplasmic reticulum, ca²⁺, t tubules, sarcolemma sarcolemma, sarcoplasmic reticulum, ca²⁺, t tubules question 22 excitation - contraction coupling begins with the depolarization at the t tubules. the production of an action potential in the sarcolemma. the release of ca²⁺ from the sarcoplasmic reticulum. the release of the cross - bridge. question 23 which of the following statements regarding the sliding filament model is false? actin and myosin do not shorten during contraction. both actin and myosin myofilaments shorten during contraction. the sarcomere shortens. the i band and h zones become narrower during contraction. the a band remains constant in length.

Explanation:

Question 21: In excitation - contraction coupling, an action potential first spreads along the sarcolemma. Then it travels down the T - tubules. This triggers the release of Ca²⁺ from the sarcoplasmic reticulum.
Question 22: Excitation - contraction coupling begins with the production of an action potential in the sarcolemma. This action potential then leads to other events in the coupling process.
Question 23: In the sliding - filament model, actin and myosin do not shorten during contraction. The sarcomere shortens as the actin filaments slide over the myosin filaments. The A band remains constant in length, and the I band and H zones become narrower. The false statement is that both actin and myosin myofilaments shorten during contraction.

Answer:

Question 21: Sarcolemma, T tubules, sarcoplasmic reticulum, Ca²⁺
Question 22: the production of an action potential in the sarcolemma.
Question 23: Both actin and myosin myofilaments shorten during contraction.