Question

Write short notes on :
(a) Muscle fatigue (b) All-or-none law (c) Oxygen debt (d) Threshold stimulus (e) Rigor mortis (f)Rib cage (g) Pectoral girdle

Answer 1

A. Muscle fatigue: Decline in the ability of the muscle to show contraction is called muscle fatigue. It can be due to vigorous exercise or abnormal fatigue can be due to the interference with the different stages of muscle contraction. Muscle fatigue can be either due to limitations of the nerve's ability to generate a sustained signal or due to the reduced ability of the muscle fibre to contract.

B. All-or-none law: It states that a minimal strength of a stimulus is required to cause the contraction of the muscle fibre to bring about the maximum contraction, and no further increase in contraction occurs by increasing the strength of the stimulus.

C. Oxygen debt: It refers to a temporary oxygen shortage in the body tissues due to extensive exercise. As a result, extra oxygen is taken up by the body during recovery from the exercise to decompose the lactic acid produced.

D. Threshold stimulus: The weakest stimulus that could generate an action potential in a neuron.

E. Rigou mortis: Extreme rigidity of the body after death is called rigor mortis. It is due to complete depletion of ATP and phosphocreatine. The contraction of the muscles is restricted due to the absence of the ATP.

F. Rib cage: There are 12 pairs of ribs which form the rib cage also called a thoracic cage. It protects the lungs and the heart.

G. Pectoral girdle: It occurs in the shoulder region. It consists of two separate halves. Each half has two bones, clavicle and scapula. It also has a glenoid cavity that provides articulation to the head of the humerus.