AP BIOLOGY

Detailed explanation-1: -Muscles are fibrous tissues that has the ability to contract. Muscles contract and relax resulting in movement of limbs. Muscles become shorter, stiffer and thicker when it contracts. It becomes longer and thinner on relaxation.

Detailed explanation-2: -Relaxation of a Skeletal Muscle The muscle fiber will repolarize, which closes the gates in the SR where Ca++ was being released. ATP-driven pumps will move Ca++ out of the sarcoplasm back into the SR. This results in the “reshielding” of the actin-binding sites on the thin filaments.

Detailed explanation-3: -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-4: -Muscle contraction occurs when muscle fibers get shorter. Literally, the muscle fibers get smaller in size. To understand how this happens, you need to know more about the structure of muscle fibers.

Detailed explanation-5: -The muscles become shorter and thicker because of contraction.