Which of the following is not a function of the skeletal system?
1. Production of erythrocytes
2. Storage of minerals
3. Production of body heat
4. Locomotion
| A. | It is initiated by a signal sent by CNS via sensory neuron. |
| B. | Neurotransmitter generates action potential in the sarcolemma. |
| C. | Increased Ca++ level leads to the binding of calcium with troponin actin filaments. |
| D. | Masking of active site for actin is activated. |
| E. | Utilising the energy from ATP hydrolysis to form cross bridge. |
| 1. | B, C and E only | 2. | C, D and E only |
| 3. | A and D only | 4. | B, D and E only |

| 1. | (a) Skeletal - Triceps (b) Smooth - Stomach (c) Cardiac - Heart |
2. | (a) Skeletal - Biceps (b) Involuntary - Intestine (c) Smooth - Heart |
| 3. | (a) Involuntary - Nose tip (b) Skeletal - Bone (c) Cardiac - Heart |
4. | (a) Smooth - Toes (b) Skeletal - Legs (c) Cardiac - Heart |
| A: | Muscle bundles are held together by collagenous connective tissue layer called fascicle. |
| B: | Sarcoplasmic reticulum of muscle fibre is a store house of calcium ions. |
| C: | Striated appearance of skeletal muscle fibre is due to distribution pattern of actin and myosin proteins. |
| D: | M line is considered as functional unit of contraction called sarcomere. |
| 1. | C and D only | 2. | A, B and C only |
| 3. | B and C only | 4. | A, C and D only |
| 1. | Actin and myosin filaments slide over each other to increase the length of the sarcomere. |
| 2. | Length of A–band does not change. |
| 3. | I–band increases in length |
| 4. | The actin filaments slide away from A–band resulting in shortening of sarcomere |
Which of the following is correct statement ?
| 1. | Actin and regulatory proteins are located in thin filament. |
| 2. | Z-lines anchor myosin (thick) filament to the ends of the sarcomere. |
| 3. | Sarcoplasmic reticulum stores acetylcholine. |
| 4. | Myosin cross bridges contain calcium binding sites. |
During muscular contraction, which of the following events occur?
| (a) | 'H' zone disappears |
| (b) | 'A' band widens |
| (c) | 'I' band reduces in width |
| (d) | Myosin hydrolyzes ATP, releasing the ADP and Pi |
| (e) | Z-lines attached to actins are pulled inwards |
Choose the correct answer from the options given below:
1. (b), (c), (d) and (e) only
2. (b), (d), (e) and (a) only
3. (a), (c), (d) and (e) only
4. (a), (b), (c) and (d) only
| 1. | binds to troponin to remove the masking of active sites on actin for myosin. |
| 2. | activates the myosin ATPase by binding to it. |
| 3. | detaches the myosin head from the actin filament. |
| 4. | prevents the formation of bonds between the myosin cross bridges and the actin filament. |
Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction:
| 1. | Calcium | 2. | Magnesium |
| 3. | Sodium | 4. | Potassium |
Sliding filament theory can be best explained as:
| 1. | when myofilaments slide past each other, actin filaments shorten while myosin filament does not shorten |
| 2. | actin and myosin filaments shorten and slide past each other |
| 3. | actin and myosin filaments do not shorten but rather slide pass each other |
| 4. | when myofilaments slide past each other, myosin filaments shorten while actin filaments do not shorten |