Question

1. Describe the process of the development of force and relaxation in smooth muscle.

Answer 1

The smooth muscle has an involuntary movement which are influenced by the electrical activity of K+ ​​​​,Na+, Ca+.The contraction of smooth muscle is innervated or caused by the stimulation of hormones, pacesetter cells or also by the autonomic nervous system. When these stimulate the contraction of smooth muscle by the calcium ions entry from the extracellular fluid.

This calcium ions will bind to the calmodulin which is a calcium binding protein. This complex of calcium calmodulin will activate the enzyme myosin light chain kinase and phosphorylating mysoin in the smooth muscle. The myosin ATPase release an energy for generating a force to contraction of smooth muscle by the phosphorylation reaction. The sliding mechanism of actin over myosin leads to shortening of smooth muscle which is known as contraction.

In the relaxation of smooth muscle there Will be act of myosin light chain phosphate which dephosphorylate the mysoin and by the latch bridge presence the normal initial length of the muscle could not be restored immediately after relaxation.