Exercises

1. Lack of relaxation between successive stimuli in sustained muscle contraction is known as _________.

Solution: Tetanus

Tetanus results in sustained muscular spasms. This is due to muscle fatigue.

2. The H -zone in the skeletal muscle fibre is due to ___________.

Solution: The central gap between actin filaments extending through myosin filaments in the A-band

H-zone in skeletal muscle is the central gap between actin filaments extending through myosin filaments in the A -band. Alternate myosin filaments in the A-band. An alternate arrangement of dark and light bands gives the striated appearance to a skeletal muscle. At the centre of A-band, a comparatively less dark zone called H -zone is present. In the centre of H-zone, M -line is present, formed by the threats that connect the myofilaments.

3. Select the correct statement with respect to locomotion in humans

a) A decreased level of progesterone cause osteoporosis in old people

b) Accumulation of uric acid crystals in joints causes their inflammation

c) The vertebral column has 10 thoracic

d) The joint between adjacent vertebrae is a fibrous joint

Solution: Accumulation of uric acid crystals in joints causes their inflammation

Inflammation of joints due to the accumulation of uric acid crystals is gout.The fibrous joint is formed by the flat skull bones, which fuse end - to -end with the help of dense fibrous connective tissue in the form of sutures to form cranium. The vertebral column is formed by 26 serially arranged units called vertebral. The less secretion of progesterone cause abortion as it basically supports a pregnancy.

4. Which of the following joints would allow no movement?

a) Fibrous joint

b) Cartilaginous joint

c) Synovial Joint

d) Ball and Socket joint

Solution: Fibrous joint

Fibrous joints are immovable joints in that occur between the bones of the cranium and in the tooth sockets. They do not allow movement because the bones are held firmly together by bundles of strong white collagen fibres. The immovable joints are often known as the sutures. The periosteum that covers the bones dips between them as a septum.

5. Stimulation of a muscle fibre by a motor neuron occurs at the _______.

Solution: Neuromuscular junction

Stimulation of a muscle fibre by a motor neurone occurs at neuromuscular junction neuron activated a muscle to contract during the excitation-contraction coupling of vertebrate skeletal muscles.

6. Select the correct statement regarding the specific disorder of muscular or skeletal system.

a) Muscular dystrophy-age related shortening of muscles

b) Osteoporosis-decrease in bone mass and higher chances of fractures with advancing age

c) Myasthenia gravis-Auto immune disorder which inhibits sliding of myosin filaments

d) Gout-inflammation of joints due to extra deposition of calcium

Solution: Osteoporosis-decrease in bone mass and higher chances of fractures with advancing age

Osteoporosis is age-related disease in which bone loose minerals and fibres from the matrix causing decreased bone mass and higher chances of fractures with advancing age. Major causative factors of osteoporosis are imbalance of hormones like calcitonin of thyroid, parathormone of parathyroids, sex hormones and deficiencies of calcium and vitamins.

7. Glenoid cavity articulates

a) clavicle with acromotion

b) scapula with acromion

c) clavicle with scapula

d) humerus with scapula

Solution: humerus with scapula

Glenoid cavity articulates humerus with scapula. It is a feature on the scapula (shoulder blade or shoulder bone). It is slightly concave from above downwards and from side to side. It is shallow and a site of attachment of glenoid labrum (glenoid ligament), which forms fibrocartilaginous rim around the glenoid cavity. It is important because it has the effect of depending the socket into which head of humerous (bone) rests, forming the shoulder joint). It represents a type of synovial, ball and socket joint.

8. The type of muscles present in our

a) heart are involuntary and unstriated smooth muscles

b) intestine are striated and involuntary

c) thigh are striated and voluntary

d) upper arm are smooth muscle fibres fusiform in shape

Solution: thigh are striated and voluntary

Thigh muscles are a skeletal muscle that is striated and voluntary skeletal muscles tissue is closely attached to skeletal bones.

9. Which one of the following is the correct description of a certain part of a normal human skeleton?

a) Parietal bone and the temporal bone of the skull are joined by fibrous joint

b) First, vertebra is axis, which articulates with the occipital condyles

c) The 9th and 10th pairs of ribs are called the floating ribs

d) Glenoid cavity is a depression to which the thigh bone articulates

Solution: Parietal bone and the temporal bone of the skull are joined by fibrous joint

Immovable or fixed or fibrous joints are found between the skull bones. No movement occurs at these joints. So, parietal bone and the temporal bone of the skull are joined by fibrous joint. Invertebrates, the first vertebra is called petals, while the second vertebra is the axis. In humans first pairs of ribs are called true ribs; 8th and 9th and 10th pairs of ribs are false ribs while 11th and 12th pairs of ribs are called floating ribs.

Glenoid cavity is a socket shaped cavity in the scapula (shoulder bone) that holds the head of the humerus in a ball and socket joint.

10. Elbow joint is an example of

a) pivot joint

b) hinge joint

c) gliding joint

d) ball and socket joint

Solution: hinge joint

In hinge joint, the convex surface of one bone fits into the concave surface of another bone. eg, knee elbow and interphalangeal joints.

Pivot joint, one bone is fixed and second articulated, eg, atlas and axial of skull rotate with axis vertebra.

Gliding joints primarily permit side-by-side and back and forth gliding movements, eg, intercarpal joints and intertarsal joints.

In ball and socket joint, a ball of one bone articulates in sockets of another bone, eg, head of the humerus and glenoid cavity of the pectoral girdle.

11. Which one of the following are the correct pairing of a body part and the kind of muscle tissue that moves it?

a) Heart wall - Involuntary unstriated muscle

b) Biceps of upper arm - smooth muscle fibres

c) Abdominal wall - Smooth muscle

d) Iris - Involuntary smooth muscle

Solution: Iris - Involuntary smooth muscle

Smooth muscles are plain, non- striated, involuntary or unstriped muscles due to the absence of striations. These occur in the walls of hollow internal organs, in capsules of lymph glands, spleen etc, in iris and ciliary body of eyes, skin dermis, penis and other accessory genitalia etc.

12. Keeping in view the 'fluid mosaic model' for the structure of cell membrane, which one of the following statements is correct with respect to the movement of lipids and proteins from one lipid monolayer to the other (described as flip-flop moment)?

a) Both lipids and proteins can flip-flop

b) While lipids and proteins can flip -flop

c) While proteins can flip-flop, lipids cannot

d) Neither lipids, nor proteins can flip-flop

Solution: While lipids and proteins can flip -flop

Singer and Nicolson (1972) suggested the widely accepted fluid mosaic model of biological membranes. According to this model, the plasma membrane contains a bimolecular lipid layer, both surface of which are interrupted by protein molecules. Some proteins are attached to the polar surface of the lipid (ie, called extrinsic protein) while, other (called intrinsic proteins) either partially entirely to stick but on both sides (called transmembrane proteins). The Movement of lipid molecules from one lipid monolayer to another monolayer is called flip-flop movement. Flip-flop movement is rarely found in lipid molecules whereas it remain absent in protein molecules.

13. Earthworms have no skeleton but during burrowing, the anterior end becomes turgid and acts as a hydraulic skeleton. It is due to

a) coelomic fluid

b) blood

c) gut peristalsis

d) setae

Solution: coelomic fluid

The body cavity (coelom) of an earthworm is filled with an alkaline, colourless or milky coelomic fluid containing water, salts, some proteins and four types of coelomic corpuscles, ie, phagocytes, mucocytes, circular nucleated cells and chloragogen cells. The coelomic fluid becomes turgid and acts as a hydraulic skeleton during burrowing.

Earthworm (Pheretime posthuma) living in burrows which are made in moist earth. It makes its burrow which is made in the moist earth. it makes its burrow partly by boring with its pointed anterior end and partly sucking and swallowing the earth. The body shows metameric segmentation. About the middle of each segment, there is a ring of tiny curved bristles called setae or chaetae, formed of any nitrogenous organic substance known as chitin. The setae and musculature serve for locomotion as well as for anchoring body firmly in the burrow.

The blood of earthworm is composed of a fluid plasma and colourless corpuscles, physiologically comparable to the leucocytes of vertebrates.

14. Which one of the following items gives its correct total number?

a) Floating ribs in humans - 4

b) Amino acids found in proteins - 16

c) Types of diabetes - 3

d) Cervical vertebrae in humans -8

Solution: Floating ribs in humans - 4

There are 12 pairs of ribs in human, which form the bony lateral walls fo the thoracic cage. The last two pairs of ribs (total four) are called floating ribs because their anterior ends are not attached to either the sternum or the cartilage of another rib. The floating ribs protect the kidneys. There are 7 cervical vertebrae in humans present in the neck. The first cervical vertebra is called atlas second is known as an axis. There are 20 amino acids found in proteins.

15. Which of the following is a flowering plant with nodules containing filamentous nitrogen-fixing micro-organism

a) Casuarina equisetifolia

b) Crotalaria juncea

c) Cycas revoluta

d) Cicer arietinum

Solution: Casuarina equisetifolia

The Casuarina tree has nitrogen fixing root nodules that harbor a filamentous streptomycete like nitrogen fixing organism called Frankia.

16. Which of the following is an example of negative feedback loop in humans?

a) Constriction of skin blood vessels and contraction of skeletal muscles when it is too cold

b) Secretion of tears after falling of sand particles into the eye

c) Salivation of mouth at the sight of delicious food

d) Secretion of sweat glands and constriction of skin blood vessels when it is too hot

Solution: Constriction of skin blood vessels and contraction of skeletal muscles when it is too cold

Skin blood vessels constrict and skeletal muscles contract due to cold is an example of negative feedback mechanism of homeostatis.

17. The contractile protein of skeletal muscle involving ATPase activity is ________.

Solution: myosin

The kinesin, myosin and dynein proteins of skeletal muscle involve ATP as activity. This cause the contraction of skeletal muscles, propelling action of cillia and flagella the intracellular transport of organelles.

18. The pivot joint between atlas and axis is a type of _________.

Solution: Saddle joint

Synovial joints are freely movable joint which allow considerable movements. Pivot joint is a type of synovial joint which provide rotational movement as in between atlas and axis vertebrae of vertebral column.

19. Out of 'X' pairs of ribs in humans only 'Y' pairs are true ribs. Select the option that correctly represents values of X and Y and provides their explanation :

a) X = 12, Y = 7 True ribs are attached dorsally to vertebral column and ventrally to the sternum

b) X = 12, Y = 5 True ribs are attached dorsally to vertebral column and sternum on the two ends

c) X = 24, Y = 7 True ribs are dorsally attached to vertebral column but are free onventral side

d) X = 24, Y = 12 True ribs are dorsally attached to vertebral column but are free on ventral side

Solution: X = 12, Y = 7 True ribs are attached dorsally to vertebral column and ventrally to the sternum

In human, 12 pairs of ribs are present in which 7 pairs of ribs (1st to 7th pairs) are attached dorsally to vertebral column and ventrally to the sternum.