MUSCLE PHYSIOLOGY

Detailed explanation-1: -For a muscle cell to contract, the sarcomere must shorten. However, thick and thin filaments-the components of sarcomeres-do not shorten. Instead, they slide by one another, causing the sarcomere to shorten while the filaments remain the same length.

Detailed explanation-2: -When all of the sarcomeres in a muscle fiber shorten, the fiber contracts. A muscle fiber either contracts fully or it doesn’t contract at all. The number of fibers that contract determines the strength of the muscular force. When more fibers contract at the same time, the force is greater.

Detailed explanation-3: -The physiological concept of muscle contraction is based on two variables: length and tension. In physiology, muscle shortening and muscle contraction are not synonymous, as tension within the muscle can be produced without changes in the length of the muscle.

Detailed explanation-4: -During muscle contraction, the I band reduces in size as the overlap between the thick filaments and the thin filaments increases. The H zone also decreases in length because of the same reason.

Detailed explanation-5: -Because the contracting fibres are pulling at an angle to the overall action of the muscle, the change in length is smaller, but this same orientation allows for more fibres (thus more force) in a muscle of a given size. Skeletal muscles are sheathed by a tough layer of connective tissue called the epimysium.