NCERT Exemplar MCQs

Hint

(c)

1. Fast muscle fibres contract spontaneously and reach anaerobic conditions in shorter time, so as to accumulate lactic acid faster in the muscles.
2. Slow muscle fibres have better ability to endure, as they are resistant to fatigue and contract slowly, it is because, of the accumulation, of large amount, of myoglobin in them.
3. Actin filament forms the isometric band in the muscle fibre because it is the only actin protein which is present in that region.
4. Sarcomere is the contractile unit of skeletal muscle.

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(b) Sternum This is a flat bone present just beneath the skin in the middle of the chest. It is about \(15 \mathrm{~cm}\) long. It consists of three parts, i.e., manubrium the uppermost part, body the middle portion, and the xiphoid process is the tip of the bone. The true ribs ( 7 pairs) are attached to the sternum. While the scapula and clavicle together constitute to form pectoral girdle, Ilium is a part of the pelvic girdle.

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(a) Pivot joint is the joints found between the atlas and axis and between the radius and ulna just below the elbow. This joint allows movement in only one plane. In a pivot joint, rounded or pointed bone fits into a shallow depression of another bone.

Whereas, saddle joint provides free movement in two planes back-forth and side to side. The projection of one bone fits in saddle-shaped depression of another bone. The joint between the carpel and metacarpel of the thumb in the hand is an example of saddle joint.

Hinge joint allows movement primarily in one plane. In a hinge joint reel (spoon) like surface of one bone fits into the concave surface of another bone for example the elbow, the knee, ankle, etc.

Gliding joint also known as plane joint, is a common type of synovial joint formed between bones that meet at flat or nearly flat articulating surface examples of gliding joint include carpel bones of the wrist and joint between the carpel and metacarpel of the palm.

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(c) The myosin filament has meromyicin and it has two important parts, a globular head, and a tail. The globular head has the site for ATPase enzyme and has binding sites for ATP and active sites for actin. This helps in the attachment of actin filament during the sliding motion. So, the correct option is ‘myosin’.

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(c) Intervertebral discs are found in the vertebral column of mammals. They are present between adjacent vertebrae from the second cervical vertebra to the sacrum. The discs form strong joints, allow various movements of the vertebral column and absorb vertical shock.

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(d) The vertebral column of the vertebrates is the modification of the notochord. The length of the human vertebral column is \(71 \mathrm{~cm}\) in males and 61 in females. In a foetus, there is only a single anterior concave curve, in adults, there are 4 curves like cervical, thoracic, lumbar and sacral.

Cervical curve is formed by 7 cervical vertebrae that start the vertebral column then we have the thoracic vertebrae which are formed by 12 thoracic vertebrae. Then the lumber which is formed by 5 lumbar vertebrae then there is sacrum which forms the sacral vertebrae and then there is coccyx. So, the correct option is Cervical – thoracic – lumbar-sacral – coccygeal.

Hint

(a) There are many joints present in the skeleton. Joint is a point of contact between two bones. The various type of joints present in the body are the Ball and socket joint Ball of one bone articulates in the socket of another bone. Head of the humerus and glenoid cavity of the pectoral girdle, femur, and acetabulum, the joint between incus and stapes.
Hinge joint movement is possible in one direction only. Joint of malleus and incus, knee joint, elbow joint, articulation joint of the lower jaw.
Pivot joint helps in turning moment. One bone is fixed and the second articulate. Atlas and axial of skull rotate with Axis vertebra
Gliding joint- limited movement in all directions. Radius and ulna
Saddle joint- It is a ball and socket-like joint but not developed fully. Metacarpals of thumb and carples of hand.
So, the correct option is ‘Hinge joint between the humerus and pectoral girdle’

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(d) Knee joint and elbow joints are examples of hinge joints. 

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(c) Some specialised cells in blood like macrophages and leucocytes exhibit amoeboid movement. They have the ability to reach the interstitial fluid by squeezing through the thin walls of blood vessels, while ciliary movement flageller movement, or gliding movement are not shown by macrophages and leucocytes.

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(d) Atherosclerosis is not related to the bone disorder. It is a condition related to arteries. Atherosclerosis is a condition where the arteries become narrowed and hardened due to a buildup of cholesterol around the artery wall.
Arthritis is the inflammation of joints.
Rickets is a disease in which weak and soft bones, stunted growth, and, in severe cases, skeletal deformities can be present. It is caused by deficiency of vitamin \(\mathrm{D}\).

Osteoporosis is a skeletal disorder in which bones get weak. It is caused by the deficiency of calcium and vitamin \(\mathrm{D}\).

Arthritis, rickets, and osteoporosis are diseases related to bone disorder. So, the correct answer is ‘Atherosclerosis’.

Hint

(c) Smooth muscles are ‘involuntary’ and non-striated muscles as they cannot be controlled directly like that of skeletal muscles which are voluntary, controlled, and possess striations. The inner walls of alimentary canal are non-striated and involuntary muscles. Rest other statements are correct.

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(b) Head of humerus bone articulates with the glenoid cavity of pectoral girdle. This articulation results in the formation of ball and socket joints, e.g., ball and socket joints present in the shoulder while other statements are incorrect.

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(b) Cardiac muscles are the ones that resemble the voluntary muscle because of the structure as they have striations in them. But the action is involuntary in nature and completely out of control of the voluntary mind. Cardiac muscles are found in the heart wall.

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\(\begin{array}{llll}\text { (b) A. } \rightarrow \text { (iv) } & \text { B. } \rightarrow \text { (iii) } & \text { C. } \rightarrow \text { (i) } & \text { D. } \rightarrow \text { (ii). }\end{array}\)
Sternum is a flat bone present just under beneath the skin in the middle of the front of the chest.

Glenoid Cavity is the depression which articulates with the head of the humerus to form the ball and socket joint in pectoral girdle.

Freely Movable Joints are characterised by the presence of a fluid filled synovial cavity between the articulating surface of the two bones. This fluids represents the synovial fluid, e.g., in gliding and hinge joints.

Cartilagenous Joints are present between the adjacent vertebrae in the vertebral column.