What is the contractile tissue of body?

The contractile tissue of the body is composed of muscle fibres, which are specialized cells that have the ability to contract and relax. There are three types of muscle fibres: skeletal muscle, smooth muscle, and cardiac muscle.

Skeletal muscle is attached to bones and is responsible for voluntary movement, such as walking, running, and talking. Skeletal muscle fibres are striated, meaning that they have a banded appearance when viewed under a microscope.

Smooth muscle is found in the walls of blood vessels, airways, and digestive organs. It is responsible for involuntary movements, such as the constriction of blood vessels and the digestion of food. Smooth muscle fibres are not striated and are spindle-shaped.

Cardiac muscle is found in the walls of the heart. It is responsible for the pumping action of the heart, which circulates blood throughout the body. Cardiac muscle fibres are striated and are branched.

Muscle fibres contract when they receive an electrical signal from a nerve cell. The electrical signal causes calcium ions to be released from the sarcoplasmic reticulum, which is a network of membranes within the muscle fibre. The calcium ions bind to proteins on the actin and myosin filaments, which are two types of protein filaments that are found in muscle fibres. The binding of calcium ions causes the actin and myosin filaments to slide past each other, which shortens the muscle fibre and causes it to contract.

After the electrical signal has stopped, the calcium ions are pumped back into the sarcoplasmic reticulum and the muscle fibre relaxes.