Free Locomotion And Movement (Daily Quiz: 1) NEET Biology Questions & Answers with Detailed Explanation & Full Review

Answer: (b)

In the given figure of human skeletal system, the marked bones (I, II, III and IV) are identified as radius, ulna, tibia and fibula respectively. Radius and ulna are two large bones of the forearm. Radius extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. Radius is a long bone, prism-shaped and slightly curved longitudinally. It articulates with the capitulum of the humerus, and with the ulna at two points: the radial notch (lower) and the head (upper part) of the ulna. Ulna runs parallel to the radius, which is shorter and smaller. The tibia and fibula are two bones of hind limbs. Tibia, also known as the shin bone, is the larger and stronger of the two lower leg bones. It forms the knee joint with the femur and the ankle joint with the fibula and tarsus. The support and movement of the tibia is essential to many activities performed by the legs, including standing, walking, running, jumping and supporting the body's weight. Fibula or calf bone is located on the lateral side of the tibia, with which it is connected above and below. It is shorter, thinner and slender.

Answer: (b)

During muscle contraction, the laterally projecting heads (cross bridges) of the thick myosin myofilaments come in contact with the thin actin myofilaments and rotate on them. This pulls the thin myofilaments toward the middle of the sarcomere, past the thick myofilaments. The Z lines come closer together and the sarcomere becomes shorter. Length of the A band remains constant. Myofilaments (both actin and myosin) stay the same length. Free ends of actin myofilaments move closer to the centre of the sarcomere, bringing Z lines closer together. I bands shorten and H zone narrows. A similar action in all the sarcomeres results in shortening of the entire myofibril and thereby of the whole fibre and the whole muscle.

Answer: (a)

The number of bones of ankle and wrist are not the same as ankle have 7 bones and wrists have 8 bone.