Question

which causes your muscles to contract?

a. drug blocking troponin-tropomyosin complex

b. ca 2+ becomes available to sarcomere

c. t-tubule depolarizes

d. a and b

e. a, b, c

Answer 1

Answer : a, b, c

Explanation : The Tropomyosin proteins prevents the binding of myosin with actin and thus prevents muscle contraction. The troponin molecule helps in keeping the Tropomyosin protein in its position by attaching to it and by forming troponin- Tropomyosin complex. So the drug which will block the troponin - Tropomyosin complex, will now allow the myosin to form a cross bridge with actin and enables muscle contraction.

Similarly, the Ca 2+ ions present in the sarcomere binds with the troponin of troponin - Tropomyosin complex and changes the shape of troponin molecule. This leads to removal of Tropomyosin from the binding site and enables formation of actin myosin cross bridge and muscle contraction. Hence, availability of Ca 2+ ions in the sarcomere helps in muscle contraction.

We know that, when a neuron depolarizes, the neuron is said to be stimulated and it transmits the signal. The T - tubules also transmits signals from the sarcolemma to the sarcoplasmic reticulum and gives signal to the sarcoplasmic reticulum to store Ca ions. Hence, the depolarization of T - tubules means that the sarcoplasmic reticulum will now contains more Ca ions and in presence of Ca ions the muscle contraction takes place.