NCERT Class 11-Biology: Chapter – 20 Locomotion and Movement Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

Get top class preparation for NSO Class-11 right from your home: fully solved questions with step-by-step explanation- practice your way to success.

Question 5:

Rahul exercises regularly by visiting a gymnasium. Of late he is gaining weight. What could be the reason? Choose the correct answer and elaborate.

a. Rahul has gained weight due to accumulation of fats in body.

b. Rahul has gained weight due to increased muscle and less of fat.

c. Rahul has gained weight because his muscle shape has improved.

d. Rahul has gained weight because he is accumulating water in the body.


b. Rahul has gained weight due to increased muscle and less of fat.

Explanation: Regular exercise leads to an increase in the amount of sarcoplasm i.e.. , the thickness of myofibrils increases along with increase in protein synthesis and mitochondria, and the reduction of body fat content occurs with the increase in the muscle mass of the human body which leads to weight gain.

Question 6:

Radha was running on a treadmill at a great speed for 15 minutes continuously. She stopped the treadmill and abruptly came out. For the next few minutes, she was breathing heavily/fast. Answer the following questions.

a. What happened to her muscles when she did strenuously exercised?

b. How did her breathing rate change?


a. Due to strenuous exercise her muscles got fatigued as the accumulation of lactic acid in the muscles occurred because the muscles did not receive adequate oxygen during the exercise and by the anaerobic respiration pathway the glucose was broken down to lactic acid due to lack of oxygen.

b. The change in the breathing rate occurred because the body demands more oxygen during strenuous exercise for more ATP (i.e.. , Energy) production. Therefore, breathing rate increases to obtain more oxygen to produce more ATP by aerobic respiration.

Question 7:

Write a few lines about Gout.


Gout is a form of arthritis which is caused by the accumulation of sodium rate crystal in the joints.

Sodium rate is a metabolic waste which gets deposited in the joints when the kidneys couldn՚t remove it due to its excessive presence in the bloodstream.

Notable symptoms of gout are intensely painful joints, redness, and swollen joints.

The symptoms of gout can be managed and reduced by Non-steroidal Anti-inflammatory drugs (NSAIDS) .

Question 8:

What is the source of energy for muscle contraction?


The source of energy for muscle contraction is ATP (Adenine Triphosphate) . An enzyme called myosin ATPase present on the head of myosin molecule breaks down into ADP and inorganic phosphate in the presence of magnesium and calcium ions and releases energy in the head of the myosin.

This energy from the ATP causes the myosin to form a cross-bridge by binding to the actin filament. The movement along the cross-bridge causes the sliding of thin and thick my filaments which initiates muscle contraction.

Question 9:

What are the points for articulation of Pelvic and Pectoral girdles?


The pectoral girdle has two bones called the clavicle and scapula which is articulated by a cavity called glenoid cavity with the head of the humerus by forming a ball and socket joint.

The pelvic girdle has three bones Ilium, Ischium, and Pubis which is articulated by a cavity called the acetabulum with the femur by forming a ball and socket joint.

Long Answer Type Questions

Question 1:

Calcium ion concentration in blood affects muscle contraction. Does it lead to tetany in certain cases? How will you correlate fluctuation in blood calcium with tetany?


Yes, in certain cases calcium ion concentration in the blood leads to tetany. Calcium plays a significant role in muscle contraction.

The parathyroid glands secretes parathyroid hormones, which increases the concentration of ions in the bloodstream.

During the deficiency of the parathyroid hormone, the concentration would decline. The decrease in the levels would result in excitability in the muscles and nerves, which results in cramps and convulsions in the muscles.

Therefore, Calcium ion concentration in the blood affects muscle contraction. When these contractions are sustained due to low levels of parathyroid hormone, which causes a decrease in the concentration and affects the muscles of larynx, hands, feet, and face, this is known as parathyroid tetany. Thus, fluctuation in blood calcium concentration can lead to tetany.