Ca⁺² bind ________ in the skeletal muscles and leads to exposure of the binding site for ________ on the filament _______:

(1) Troponin, myosin, actin                

(2) Troponin, actin, relaxin

(3) Actin, myosin, troponin                

(4) Tropomysin, myosin, actin

Following is the figure of actin (thin) filaments. Identify A, B and C:

(1) A - Tropomyosin, B - Troponin, C - F-actin

(2) A - Troponin, B - Myosin, C - Tropomyosin

(3) A - Troponin, B - Tropomyosin, C - Myosin

(4) A - Troponin, B - Tropomyosin, C - F-actin

The above figure is related with myosin monomer (meromyosin). Identify A to C:

(1) A - head, B - cross arm, C - GTP binding sites

(2) A - head, B - cross arm, C - Ca⁺² binding sites

(3) A - head, B - cross arm, C - ATP binding sites

(4) A - cross arm, B - head, C - ATP binding sites

The action potential that triggers a muscle contraction travels deep within the muscle cell by means of:

(1) Sarcoplasmic reticulum                

(2) Transverse tubules

(3) Synapse                                      

(4) Motor end plates

ATP provides energy for muscle contraction by allowing for:

(1) An action potential formation in the muscle cell

(2) Cross-bridge attachment of myosin to actin

(3) Cross-bridge detachment of myosin from actin

(4) Release of Ca⁺² from sarcoplasmic reticulum

A motor unit is best described as:

(1) All the nerve fibres and muscle fibres in a single muscle bundle

(2) One muscle fibre and its single nerve fibre

(3) A single motor neuron and all the muscle fibres that it innervates

(4) It is the neuron which carries the message from muscle to CNS

Electrical excitation in a muscle fibre most directly causes:

(1) Movement of tropomyosin

(2) Attachment of the cross bridges to actin

(3) Release of Ca⁺² from sarcoplasmic reticulum

(4) Splitting of ATP

The energy for muscle contraction is most directly obtained from:

(1) Phosphocreatine                          

(2) ATP

(3) Anaerobic respiration                   

(4) Aerobic respiration

Put the following phrases in proper order to describe what occurs at the neuromuscular junction to trigger muscle contraction:
I. Receptor sites on sarcolemma.
II. Nerve impulse.
III. Release of Ca⁺² from sarcoplasmic reticulum
IV. The neurotransmitter acetylcholine is released
V. Sarcomere shortern
VI. Synaptic cleft
VII. Spread of impulses over sarcolemma on T-tubules
(1) II, IV, I, VI, VII, III, V           

(2) II, IV, VI, I, VII, III, V

(3) I, II, III, IV, V, VI, VII             

(4) VII, VI, V, IV, III, II, I

Go through the following diagram describing muscle contraction:

Now identify A to E:
(1) A - Cross bridge, B - Cross bridge formation, C - Breaking of cross bridge, D - Sliding (rotation), E - ATP

(2) A - Cross bridge, B - Cross bridge formation, C - Sliding / rotation, D - Breaking of cross bridge, E - ATP

(3) A - Cross bridge, B - Breaking of Cross bridge, C - sliding / rotation, D - Cross bridge formation, E - AMP

(4) A - Cross bridge, B - Cross bridge formation, C - Sliding / rotation, D - ADP, E - Breaking of cross bridge