Choose the correct statement.

1. In a resting muscle fibre, a subunit of troponin masks the active binding sites on myosin for actin filaments

2. The myosin monomer called meromyosin has a globular head which has binding sites for ATP and active sites for actin

3. A motor neuron along with the muscle fibres connected to it constitute motor-end plate

4. The Z-lines attached to A-bands are pulled inwards towards the H-zone causing shortening of sarcomere

Each myosin filament comprises all the following,

except

(1) Each myosin filament is a polymerised protein, many monomeric proteins called meromyosins constitute one thick filament

(2) Actin binding sites and ATP binding sites are present on the cross-arm which is part of HMM

(3) Myosin tail is composed of LMM which binds to tropomyosin

(4) The globular head of myosin is an active ATPase enzyme

The fusion of which set of bones forms the coxal bone of the pelvic girdle?

(1) Malleus, incus and stapes

(2) Ilium, scapula and ischium

(3) Ilium, ischium and pubis

(4) Incus, ilium and sternum

Sarcomere is described as the part of myofibril between two

(1) M-lines

(2) Z-lines

(3) A-bands

(4) I-bands

Identify the structure marked ‘X’

1. Humerus

2. Radius

3. Scapula

4. Clavicle

Red muscle fibres differs from white muscle fibres in having

1. More sarcoplasmic reticulum

2. Less myoglobin content

3. More number of mitochondria

4. High lactic acid due to anaerobic oxidation

In a healthy person, the red muscle fibres appear red due to stored

1. Carboxyhemoglobin

2. Carbaminohemoglobin

3. Myoglobin

4. Erythropoietin

Arrange the following events involved in muscular contraction

(i) Action potential enters muscle fibre through T-tubules

(ii) Ca²⁺ binds with troponin-C

(iii) Actomyosin cross bridge formation

(iv) Sliding of thin myofilament along the thick myofilament

(v) Exposure of active sites on actin filaments

(vi) Release of Ca²⁺ from sarcoplasmic reticulum

1. $\left(\mathrm{i}\right)\to \left(\mathrm{ii}\right)\to \left(\mathrm{iii}\right)\to \left(\mathrm{iv}\right)\to \left(\mathrm{v}\right)\to \left(\mathrm{vi}\right)$

2. $\mathrm{(vi)\to (v)\to (iv)\to (iii)\to (ii)\to (i)}$

3. $\left(\mathrm{i}\right)\to \left(\mathrm{ii}\right)\to \left(\mathrm{vi}\right)\to \left(\mathrm{v}\right)\to \left(\mathrm{iii}\right)\to \left(\mathrm{iv}\right)$

4. $\left(\mathrm{i}\right)\to \left(\mathrm{vi}\right)\to \left(\mathrm{ii}\right)\to \left(\mathrm{v}\right)\to \left(\mathrm{iii}\right)\to \left(\mathrm{iv}\right)$

The total number of bones in the limb of a man is

1.  24

2.  30

3.  14

4.  21

Which of the following are involved in the formation of acetabulum?

a. llium

b. ischium

c. Pubis

1.  a & b only

2.  b & c only

3.  a & c only

4.  a, b & c