What are the differences between smooth and skeletal muscle excitation-contraction dynamics (focus on Ca2+), Also, what...

What are the differences between smooth and skeletal muscle excitation-contraction dynamics (focus on Ca2+),

Also, what are the specific receptors, kinases, and pumps involved in each?

Expert Solution

Both the smooth muscle and skeletal muscle contraction occur by cross bridging of myosin (protein filament) over actin filament but the process that gives rise to this are different in both the muscles.

The smooth muscle contraction is controlled by autonomous nervous system while the somatic nervous system controls skeletal muscle contraction.

Once an action potential is generated, calcium ions are influxedd in the cytoplasm of both the muscle fibres.

In smooth muscle: Most of the calcium ions in smooth muscles sarcoplasm are influxed by the opening of special calcium channels by the signals of neurotransmitters released by the autonomic nervous system. While most of the calcium is extra-cellular, some of it is also released from the sarcoplasmic reticulum on excitation of the cell. Once inside, the calcium binds to a protein and forms a complex known as calcium calmodulin complex which binds to and activates and enzyme- myosin light chain kinase- that phosphates the myosin head and increses its affinity to bind with its binding site on actin, thus resulting in muscle contraction by sliding motion using energy in the form of ATP.

In skeletal muscle- on excitation by the action potential, some of the calcium channels open which cause influx of calcium in the sarcoplasm. This calcium stimulates the sarciplasmic reticulum to release more calcium in the sarcoplasm. This calcium binds to a protein- troponin, which covers the binding site of myosin head on actin. Once the calcium binfs with troponin, the binding site is free and the myosin head binds to actin and causes contraction by sliding using ATP.

Sydney Mullin answered 1 year ago

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