The contractile protein of skeletal muscle involving ATPase activity is :

1. tropomyosin                 

2. myosin       

3. $\mathrm{\alpha }$-actinin                     

4. troponin

Prostaglandins have no role in 

1. inflammatory and allergic reactions

2. blood clotting 

3. smooth muscle contraction

4. conduction of nerve impulses.

If a stimulus, several times greater than the threshold stimulus is provided to a muscle

fibre, it will

1. Contract with a larger force

2. Contract with a smaller force

3. Contract with a same force

4. undergo tetany

Which one of the following is a sesamoid bone?

1. Pelvis                             

2. Patella 

3. Pterygoid                       

4. Pectoral girdle

Given diagram shows bone of the left human hindlimb as seen from front. It has certain mistakes in labeling. Two of the wrongly labelled bones are

(1) tibia and tarsals 

(2) femur and fibula

(3) fibula and phalanges

(4) tarsals and femur 

Which of the following is correct about the given figure?

(1) The length of the thick and thin myofilaments has changed.

(2) Length of both anisotropic and isotropic band has changed.

(3) The myosin cross-bridges move on the surface of actin and the thin and thick myofilaments slide past each other.

(4) Length of the sacromere remains same.

Skeletal muscles appear striated due to the presence of two characteristic proteins in alternating dark and light bands. Which of the following is a correct match of the protein with its light refractive property and color?

       Protein                  Colour                 Property

(1)  Myosin                   Light                 Anisotropic

(2)  Actin                      Dark                 Anisotropic

(3)  Myosin                   Dark                  Isotropic

(4)  Actin                      Light                  Isotropic

During muscular contraction, which of the following events occur?

(i)   H-zone disappears

(ii)  A band widens

(iii)  I band shortens

(iv)  Width of A band is unaffected

(v)  M line and Z line come closer

(1)  (i),(iii),(iv) and (v)

(2)  (i),(ii) and (v)

(3)  (ii),(iv) and (v)

(4)  (i),(ii) and (iii).

Which of the following is true for the labelled parts in the figure below?

(1) A - Z-line              - located at centre of I - band

(2) B - Thin filament   - occurs in A-band only

(3) C - Thick filament  - confined to I-band

(4) D - H-zone           - located at centre of M-line

The H-Zone in the skeletal muscle fibre is due to 

(1) the central gap between actin filaments extending through myosin filaments in the A-band

(2) extension of myosin filaments in the central portion of the A-band

(3) the absence of myofibrils in the central portion of A-band

(4) the central gap between myosin filaments in the A-band