Question

Describe the isotonic and isometric contractions.

Answer 1

The muscle in the human body get contracted whenever any work is done. These contractions are of two types of isotonic contraction in this length of muscle changes and second isometric contraction where there is no change in length of the muscle.

Complete answer: The human body comprises three types of muscle tissues; smooth muscles, cardiac muscles and skeletal muscles. Smooth muscles are involuntary muscles and non-striated in appearance. They are associated with organs and systems like the digestive system, respiratory system, etc. Cardiac muscles are striated (having a repeating functional unit called sarcomeres) in appearance and are involuntary. These are found in cardiac tissues that help them for synchronic contraction. Skeletal muscles are voluntary muscles and striated with sarcomeres. Sarcomeres of skeletal muscles shorten when an object is moved. The force generated by the shortening of the muscle is called muscle tension. However, muscle tension can be seen even when a muscle is contracting against a load that does not move. These contractions are of two types:
a) Isotonic contraction: In isotonic contraction, the tension in the muscle is constant, a load is moved as the length of the muscle changes. There are two types of isotonic contractions; concentric contraction: Involves muscle contraction to move a load. Ex. When a hand weight is brought up, the brachial muscle of the biceps contracts. The length of the muscle is shortened. Eccentric contractions: This occurs when the tension in the muscles is released and the muscle length is increased. Ex. When the hand weight is lowered.
b) Isometric contraction: It occurs when the muscle produces a tension without changing the length of the muscles. E.g. If someone attempts to lift a hand weight that is too heavy. Here, sarcomere contraction occurs, but the load is not moved. Isometric contraction is responsible for maintaining our body posture and bone-joint stability.

Note: All these muscle activities are under the control of the nervous system. Neural control regulated the concentric, eccentric, and isometric contractions of the muscles. Many actions of our body are the result of the combination of both isotonic and isometric contractions.