NCERT Exemplar Class 11 Biology Solutions Locomotion and Movement

Multiple Choice Questions
1.Match the following and mark the correct option
Column-1                       Column-ll
A.Fast muscle fibres   (i) Myoglobin
B.Slow muscle fibres (ii)Lactic acid
C.Actin filament         (iii)Contractile unit
D.Sarcomere                (iv)l-band
(a) A-(i),  B-(ii), C-(iv),  D-(iii)
(b) A-(ii), B-(i),  C-(iii), D-(iv)
(c) A-(ii),  B-(i),  C-(iv), D-(iii)
(d) A-(iii), B-(ii),C-(iv), D-(i)

2.Ribs are attached to
(a) scapula (b) sternum
(c) clavicle (d) ilium.
Solution. (b) : There are 12 pairs of ribs. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to sternum

3.What is the type of movable joint present between the atlas and axis?
(a) Pivot (b) Saddle
(c) Hinge (d) Gliding
Solution. (a): Pivot joint allows only a rotatory movement of one bone on the other, which remains stationary. A rounded end of one  bone fits into a shallow pit of another bone. e.g., joint between atlas and axis vertebrae which enables the head to turn from side to side.

4.ATPase of the muscle is located in
(a) actinin (b) troponin
(c) myosin (d) actin.
Solution. (c): The head of each myosin molecule contains an enzyme myosin ATPase. In the presence of myosin ATPase, Ca2+ and Mg2+ ions, ATP breaks down into ADP and inorganic phosphate, releasing energy in the head.

5.Intervertebral disc is found in the vertebral column of
(a) birds
(b) reptiles
(c) mammals
(d) amphibians.
Solution.(c) : Intervertebral discs are found in the vertebral column of mammals. They are present between adjacent vertebrae from second cervical vertebra to the sacrum. The discs form strong joints, allow various movements of the vertebral column and absorb vertical shock.

6.Which one of the following is showing the correct sequential order of vertebrae in the vertebral column of human beings?
(a) Cervical – lumbar – thoracic – sacral – coccygeal
(b) Cervical – thoracic – sacral – lumbar – coccygeal
(c) Cervical – sacral – thoracic – lumbar – coccygeal
(d) Cervical – thoracic – lumbar – sacral – coccygeal
Solution.(d) : Cervical vertebrae are present in neck region. Thoracic vertebrae are present in the chest region. Lumbar vertebrae are present in abdomen. Sacrum is present in hip area and coccyx is considered as vestigial tail.

7.Which one of the following options is incorrect?
(a) Hinge joint – between humerus and pecto-ral girdle
(b) Pivot joint – between atlas, axis and occipital condyle
(c) Gliding joint – between the carpals
(d) Saddle joint – between carpal and metacar- pals of thumb
Solution. (a): A hinge joint allows movement in one plane. Spool (reel) like surface of one bone fits into the concave surface of another bone. The elbow, the knee, ankle and interphalangeal joint are examples of hinge joint. Joint between humerus and pectoral girdle is an example of ball and socket joint.

8.Knee joint and elbow joints are examples of
(a) saddle joint
(b) ball and socket joint
(c) pivot joint
(d) hinge joint.
Solution. (d): Refer answer 7.

9.Macrophages and leucocytes exhibit
(a) ciliary movement
(b) flagellar movement
(c) amoeboid movement
(d) gliding movement.
Solution. (c): Macrophages and leucocytes exhibit amoeboid movement which is effected by pseudopodia due to the streaming of protoplasm.

10.Which one of the following is r .sorder of bone?
(a) Arthritis (b) Osteoporosis
(c) Rickets (d) Atherosclerosis
Solution.(d) : Atherosclerosis is a disorder of circulatory system.

11.Which one of the following statements is  incorrect?
(a) Heart muscles are striated and involuntary.
(b) The muscles of hands and legs are striated and voluntary.
(c) The muscles located in the inner walls of alimentary canal are striated and involuntary.
(d) Muscles located in the reproductive tracts are unstriated and involuntary.
Solution.(c) : Skeletal or striated or voluntary muscles are found in the limbs, body wall, tongue, pharynx and beginning of oeso-phagus. These animals are under the control of animals will. Smooth or nonstriated or involuntary muscles are found in the posterior part of the oesophagus, stomach, intestine, lungs, urinogenital tract, etc. Action of these muscles is controlled by autonomic nervous system and they are not under the control of animal’s will. Cardiac muscles are found in the walls of the heart and in the walls of large veins. There fibres show the characters of both unstriped and striped muscle fibres and are involuntary.

12. Which one of the following statements is true?
(a) Head of humerus bone articulates with acetabulum of pectoral girdle.
(b) Head of humerus bone articulates with glenoid cavity of pectoral girdle.
(c) Head of humerus bone articulates with a cavity called acetabulum of pelvic girdle.
(d) Head of humerus bone articulates with a glenoid cavity of pelvic girdle.
Solution. (b): Each pectoral girdle consists of two bones : 1 clavicle and 1 scapula. At the point where the superior and lateral borders of the scapula meet, there is the lateral angle which presents a shallow articular surface termed as glenoid cavity into which the head of the humerus articulates.

13.Muscles with characteristic striations and  involuntary are
(a) muscles in the wall of alimentary canal
(b) muscles of the heart
(c) muscles assisting locomotion
(d) muscles of the eyelids.
Solution. (b) : Refer answer 11.

14.Match the following and mark the correct option.
Column-1                     Column-ll
A.Sternum                   (i)Synovial fluid
B.Glenoid cavity        (ii) Vertebrae
C.Freely movable      (iii) Pectoral girdle joint
D.Cartilaginous          (iv) Flat bones joint
(a) A-(ii),   B-(i),   C-(iii), D-(iv)
(b) A-(iv),  B-(iii), C-(i),   D-(ii)
(c) A-(ii),   B-(i),   C-(iv), D-(iii)
(d) A-(iii), B-(i),   C-(ii),  D-(iv)

Short Answer Type Questions
1.Name the cells/tissues in human body which
(a) exhibit ameboid movement
(b) exhibit ciliary movement
Solution.(a) Leucocytes, (b) Ciliated epithelium of trachea.

2.Locomotion requires a perfect coordinated activity of muscular_________systems.
Solution.skeletal and neural.

3.Sarcolemma, sarcoplasm and sarcoplasmic reticulum refer to a particular type of cell in our body. Which is this cell and to what parts of that cell do these names refer to?
Solution.The terms are referred to muscle fibre Sarcolemma – Plasma membrane Sarcoplasm – Cytoplasm Sarcoplasmic reticulum – Endoplasmic reticulum

4.Label the different components of actin filament in the diagram given below.

5.The three tiny bones present in middle ear are called ear ossicles. Write them in correct sequence beginning from ear drum.
Solution. Malleus, incus, stapes.

6.What is the difference between the matrix of bones and cartilage?
Solution. Bone has a very hard matrix due to calcium salts in it and cartilage has slightly pliable matrix due to presence of chondroitin

7.Which tissue is afflicted by Myasthenia gravis? What is the underlying cause?
Solution.Muscular tissue is affected by myasthe  nia gravis. It is an auto-immune disorder.

8.How do our bone joints function without grinding noise and pain?
Solution.In cartilaginous joints, white fibro cartilage present between the ends of bones and in synovial joints, synovial fluid present’ between articulating surface of two bones enclosed within synovial cavity make our joints to function without grinding noise and pain.

9.Give the location of a ball and socket joint in a human body.
Solution.Ball and socket joint is present between glenoid cavity of the pectoral girdle and head of the humerus and between acetabulum of pelvic girdle and head of femur.

10.Our fore arm is made of three different bones. Comment.
Solution.Our fore arm is made of radius, ulna and carpals.

Short Answer Type Questions
1.With respect to rib cage, explain the following:
(a) Bicephalic ribs
(b) True ribs
(c) Floating ribs
Solution.(a) Ribs have two articulation surfaces on their dorsal end and hence are called bicephalic.
(b) first 7 pairs of ribs are called true ribs. Dorsally, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.
(c) Last two pairs of ribs (11th and 12th) are called floating ribs as their anterior ends are not attached to either the sternum or the cartilage of another rib.

2.In old age, people often suffer from stiff and inflamed joints. What is this condition called? What are the possible reasons for these symptoms?
Solution. The condition is called arthritis. It is of two types:
(i) Rheumatoid arthritis is the most common arthritis. It is an inflammation of the synovial membrane in synovial joints. When this membrane, which is a source of synovial fluid, becomes inflamed, it produces too much fluid. The joints swell and become very painful.
(ii)Osteoarthritis affects the articular carti-lage at the synovial joints. The cartilage erodes and due to proliferation new bone is deposited. It is a degenerative joint disease in which joints become painful and stiff with restricted movement.

3.Exchange of calcium between bone and extra-cellular fluid takes place under the influence of certain hormones.
(a) What will happen if more of Ca++ is in extracellular fluid?
(b) What will happen if very less amount of Ca++ is in the extracellular fluid?
Solution.(a) Exchange of calcium between bone and extracellular fluid takes place under the influence of calcitonin and parathyroid hormones. Calcitonin hormone will then lower the calcium level by suppressing release of calcium ions from the bones.
(b) Parathyroid hormone will mobilise the release of calcium into the extracellular fluid from the bones.

4.Name atleast two hormones which result in fluctuation of Ca++ level.
Solution.Calcitonin and parathyroid hormone.

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 accumula-tion 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.
Solution. (b) Rahul has gained weight because with regular exercise, myofibrils increase in thickness and protein synthesis also increases resulting in increase in volume of muscles. Thus, muscles become denser. With regular exercise the body fat burns.

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 exercised strenuously?
(b) How did her breathing rate change?
Solution.(a) Her muscles got fatigued. During’ strenuous exercise, muscles do not get enough oxygen and in the absence of oxygen, there is anaerobic breakdown of glycogen into lactic acid. Accumulation of lactic acid leads to muscle fatigue.
(b) After strenuous exercise, first she breaths faster for sometime so as to supply extra oxygen for oxidising excess lactic acid. When the lactic acid got oxidised, again her breathing rate came back to normal.

7.Write a few lines about gout.
Solution.Gout is inflammation of joints. It results due to accumulation of uric acid crystals in synovial joints. This accumulation makes movement both difficult and painful.

8.What is the source of energy for muscle contraction?
Solution. ATP is the source of energy for muscle contraction. The head of each myosin molecule contains an enzyme, myosin ATPase. In the presence of ATPase, Ca2+,  Mg2+         ions, ATP breaks down into ADP and inorganic phosphate, releasing energy in the head of myosin. Energy from ATP causes energized myosin cross bridges to bind to actin. The energised cross-bridges move, causing thin myofilaments to slide along the thick myofilaments, thus initiating muscle contraction.

9.What are the points for articulation of pelvic and pectoral girdles?
Solution. Pelvic girdle has a cavity called acetabulum to which the thigh bone (femur) articulates. Pectoral girdle has a process called acromion to which the clavicle articulates and a glenoid cavity which articulates with the head of the humerus.

Long Answer Type Questions
1.Calcium ion concentration in blood affects muscle contraction. Does it lead to tetany in 3. certain cases? How will you correlate fluctuation  in blood calcium with tetany?
Solution. Calcium plays a important role in the regulation of muscle contraction. Parathyroid hormone (PTH) secreted by parathyroid gland increases calcium level in the blood.
In hypoparathyroidism (deficiency of PTH), calcium level in the blood falls. This increases the excitability of nerves and muscles, causing cramps and convulsions. Sustained contractions of the muscles of larynx, face, hands and feet are produced. This disorder is called parathyroid tetany.

2.An elderly woman slipped in the bathroom and had severe pain in her lower back. After X-ray examination doctors told her, it is due to a slipped disc. What does that mean? How does it affect our health?
Solution.The intervertebral discs present in between the vertebrae protect the bones by absorbing the shocks from daily activities like walking, lifting and twisting.
Each vertebral disc has two parts, a soft gelatinous inner portion and a tough outer ring. Injury or weakness can cause the inner portion of the disk to protrude through the outer ring. This is called slipped disc.
A slipped disc can place extra pressure on the nerves and muscles around it. This can adversely affect our health in the following ways:
(i) Causes pain and numbness, most commonly on one side of the body.
(ii)Causes pain that extends to our arms and or legs.
(iii)Causes pain that worsens at night.
(iv)Causes pain that worsens after standing sitting or walking.
(v) Causes unexplained muscle weakness.
(vi)Causes tingling, aching or burning sensations in the affected area. An untreated severe slipped disc can lead to permanent nerve damage. In very rare cases, a slipped disc can cut off nerve impulses to the cauda equina nerves in lower back and legs. If this occurs, we s may lose bowel or bladder control.

3.Explain sliding filament theory of muscle contraction with neat sketches.
Solution.Sliding filament theory states that contraction of a muscle fibre takes place by the sliding of thin filaments over the thick filaments. Muscle contraction is initiated by a neural signal sent by CNS to neuromuscular junction via a motor  neuron. The signal reaching the junction releases a neurotransmitter (acetylcholine)which generates an action potential in the sarcolemma. This spreads through the muscle A fibre and causes the release of calcium ions into the sarcoplasm. Increase in Ca2+ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, A myosin head now binds to the exposed active sites on actin to form a cross bridge. This leads to pulling of attached actin filaments towards the centre of ‘A’ band. The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e.,contraction. During contraction of the muscle the T bands reduce, whereas the ‘A’ bands retain the length. The myosin, releasing the ADP and Pi goes back to its relaxed state. A new ATP binds and the cross bridge is broken. The ATP is again hydrolysed by the myosin
head and the cycle of cross bridge formation and breakage is repeated causing further sliding. This process continues till the Ca2+ ions are pumped back to the sarcoplasmic reticulum resulting in the masking of actin filaments. This leads to the return of “ZI lines back to their original position i.e., relaxation.

4.How does a muscle shorten during its contraction and return to its original form during relaxation?
Solution. Refer answer 3.

5.Discuss the role of Ca2+ ions in muscle contraction. Draw neat sketches to illustrate your answer.
Solution. Calcium plays a key regulatory role in muscle contraction. During muscle contraction, an action potential passes from  the motor end plate over the sarcolemma and then into the T-tubules and sarcoplasmic reticulum and stimulates it to release Ca2+ ions into the sarcoplasm.  The calcium ions bind to troponin causing a change in its shape and position. This in turn alters shape and the position of tropomyosin, to which troponin binds. This shift exposes the active sites on the F-actin molecules. Myosin cross-bridges are then able to bind to these active sites.

6.Differentiate between pectoral and pelvic girdle.
Solution. Differences between pectoral girdle and pelvic girdle are: