Explain the role of Ca2 in the contractile mechanism both in

Explain the role of Ca2+ in the contractile mechanism; both in the presynapse and in a muscle cell.

Solution

Synapse is a structure in the nervous system that permits a neuron (or the nerve cell) to pass an electrical or the chemical signal to another neuron. Presynaptic and postsynaptic sites contain extensive array of molecular machinery that link the two membranes ( one neuron to another) together to carry out signaling process. The signalling process takes place with the help of Voltage Dependent Calcium channels (VDCc). These are a group of voltage gated ion channels which are found on the membrane of neuron which have the permeability to Calcium ions and very slightly to sodium ions. The concentration of calcium is very much higher on the outside of the membrane than inside. When VDCc are excited, the calcium ions rush into the cell which in turn results in the activation of the cell to pass a signal. The calium ions cause the acetylcholine vesicles attached to the presynaptic membrane to release acetylcholine via exocytosis into the synaptic cleft.

Smooth muscle contraction is controlled by calcium ions. Influx of calcium ions control the contraction mechanism of sarcomeres, the basic unit of muscle cells.