31 Years NEET Previous Year Questions: Locomotion And Movement- 2 - NEET MCQ

Myasthenia gravis: Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.
Tetany: Rapid spasms (wild contractions) in muscle due to low Ca++ in body fluid.
Arthritis: Inflammation of joints.
Osteoporosis: Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.
Gout: Inflammation of joints due to accumulation of uric acid crystals.

(a) There are 12 pairs of ribs. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. Last 2 pairs (11th and 12th) of ribs are not connected ventrally and are therefore, called floating ribs.
(b) & (c) 
Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs. The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion. The clavicle (collar bone) articulates with this.
(d) Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint.

Musculardys trophy is a group of muscle diseases, marked by weakness and wasting of selected muscles, in which there is a recognizable pattern of inheritance.

In this disorder, the mutated gene on middle of the short arm of X - chromosome is unable to produce a protein dystrophin in skeletal muscles. It is common in males, female heterozygous carriers are normal.

Calciumion plays an important role in skeletal muscle contraction. Muscle contraction is initiated by signal sent by the central nervous system. The neural signal further spreads through the muscle fibre and causes the release of calcium ions. Increase in calcium ion levels lead to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.

The pivot joint is a type of synovial joint. Synovial joints allow considerable movement. Fibrous joints do not allow any movement, cartilaginous joints allow only limited movements.

Osteoporosis is reduction in bone mineral density, resulting in bones that are brittle and liable to fracture. Infection, injury and synovitis can cause localised osteoporosis of adjacent bone, Generalised osteoporosis is common in the elderly and in women after menopause. After menopause the estrogen levels in blood plasma are much reduced. Estrogen helps to regulate bone cells called osteoclasts which are responsible for building new bone. When estrogen levels drop fewer osteoclasts are produced resulting in osteoporosis.

Calciumion plays an important role muscle contraction. Calcium ions bind to troponin causing a change in its shape and position. Thus in turn alters shape and position of tropomyosin to which troponin binds. This shift exposes the active sites on F-actin molecules. Myosin cross-bridge are then able to bind to these active sites.

Sliding filament theory was given by Huxley and Huxley (1954). It states that Actin and Myosin filaments do not become short but rather slide pass each other. Because of sliding of actin filaments over myosin the length of I-band will change.

A gliding joint is a common type of synovial joint formed between bones that meet at flat or nearly flat articular surfaces. Gliding joints allow the bones to glide past one another in any direction along the plane of the joint - up and down, left and right, and diagonally. Many gliding joints are formed in the appendicular skeleton between the carpal bones of the wrist; between the carpals and the metacarpals of the palm; between the tarsal bones of the ankle; and between the tarsals and the metatarsals of the foot.

Fibrous joint is an attachment between bones, being held together by fibrous connective tissue. For example- suture between skull bones.