Animal Physiology Question 1. Smooth muscle, like striated muscle, utilizes Ca2+ as a signal molecule that...

Animal Physiology Question

1. Smooth muscle, like striated muscle, utilizes Ca2+ as a signal molecule that can allow contraction to occur. However, smooth muscle does not have troponin or tropomyosin. Therefore, Ca2+ must interact with other proteins. Describe these relationships.

Expert Solution

Unlike skeletal muscle and cardiac muscle, smooth muscle does not contain calcium binding protein, troponin, contraction is initiated by protein calmodulin, as opposed to calcium activated troponin system.

In response to a stimuli in smooth muscle, the intracellular concentration of calcium increases and this activated calcium combines with protein calmodium, The calcium calmodulin complex then activates an enzyme called myosin (light chain) kinase, which, in turn, activates the myosin heads by phosphorylating them. The heads can then attach to actin-binding sites and pull on the thin filaments.

Smooth muscle fibers have a limited calcium-storing sarcoplasmic reticulum but have calcium channels in the sarcolemma that open during the action potential along the sarcolemma. The influx of extracellular calcium ions, which diffuse into the sarcoplasm to reach the calmodulin, accounts for most of the calcium that triggers contraction of a smooth muscle cell

Sydney Mullin answered 1 year ago

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