Question 1

Q1: Draw the diagram of a sarcomere of skeletal muscle showing different regions.

Accepted Answer

A diagram of a sarcomere shows the functional unit of a myofibril, located between two successive 'Z' lines. A labelled diagram would include the following regions and structures, as depicted in Figure 17.2 of the textbook:    Z line: An elastic fibre that bisects the I-band. The thin filaments are...

Question 2

Q10: Fill in the blank spaces: (a) All mammals (except a few) have ________ cervical vertebra. (b) The number of phalanges in each limb of human is _______...

Accepted Answer

(a) All mammals (except a few) have seven cervical vertebra. (b) The number of phalanges in each limb of human is 14 (c) Thin filament of myofibril contains 2 'F' actins and two other proteins namely tropomyosin and troponin. (d) In a muscle fibre Ca$^{++}$ is stored in sarcoplasmic reticulum (e) 11...

Question 3

Q2: Define sliding filament theory of muscle contraction.

Accepted Answer

The sliding filament theory is the most widely accepted explanation for the mechanism of muscle contraction. It states that the contraction of a muscle fibre occurs by the sliding of the thin filaments (actin) over the thick filaments (myosin) within the sarcomere. This sliding movement pulls the Z...

Question 4

Q3: Describe the important steps in muscle contraction.

Accepted Answer

The important steps in the mechanism of muscle contraction, according to the sliding filament theory, are as follows: 1.  Initiation by Neural Signal: The process begins when a signal is sent from the central nervous system (CNS) via a motor neuron to the neuromuscular junction (motor-end plate). 2....

Question 5

Q4: Write true or false. If false change the statement so that it is true. (a) Actin is present in thin filament (b) H-zone of striated muscle fibre repre...

Accepted Answer

(a) True. (b) False. The correct statement is: H-zone of a striated muscle fibre represents only thick filaments. (c) True. (d) False. The correct statement is: There are 12 pairs of ribs in man. (e) True.

Question 6

Q5: Write the difference between : (a) Actin and Myosin (b) Red and White muscles (c) Pectoral and Pelvic girdle

Accepted Answer

Question 7

Q6: Match Column I with Column II : Column I (a) Smooth muscle (b) Tropomyosin (c) Red muscle (d) Skull Column II (i) Myoglobin (ii) Thin filament (iii) S...

Accepted Answer

The correct matches are:    (a) Smooth muscle - (iv) Involuntary (Smooth muscles, like those in the digestive tract, are not under voluntary control.)    (b) Tropomyosin - (ii) Thin filament (Tropomyosin is a protein that is a component of the actin or thin filament.)    (c) Red muscle - (i) Myoglob...

Question 8

Q7: What are the different types of movements exhibited by the cells of human body?

Accepted Answer

The cells of the human body exhibit three main types of movements: 1.  Amoeboid Movement: This movement is effected by pseudopodia formed by the streaming of protoplasm. It is seen in specialised cells like macrophages and leucocytes (white blood cells) in the blood. Cytoskeletal elements like micro...

Question 9

Q8: How do you distinguish between a skeletal muscle and a cardiac muscle?

Accepted Answer

Question 10

Q9: Name the type of joint between the following:- (a) atlas/axis (b) carpal/metacarpal of thumb (c) between phalanges (d) femur/acetabulum (e) between cr...

Accepted Answer

(a) atlas/axis: Pivot joint (b) carpal/metacarpal of thumb: Saddle joint (c) between phalanges: Hinge joint (d) femur/acetabulum: Ball and socket joint (e) between cranial bones: Fibrous joint (sutures) (f) between pubic bones in the pelvic girdle: Cartilaginous joint (pubic symphysis)

NCERT Solutions