MICROANATOMY

MUSCLE NERVE CARTILAGE BONE

SKELETAL MUSCLE

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

Which of the following occurs first in muscle contraction?

A	Calcium Ion Enters the Pre-synaptic Terminal
B	Acetylcholine Enters the Synaptic Cleft
C	Sodium Ion Enters the Sarcolemma
D	Calcium Ion Enters the Sarcoplasm (Cytoplasm).

Explanation:

Detailed explanation-1: -The correct answer is (c): calcium ions enter the synaptic bulb. Triggering the contraction of skeletal muscle fibers involves the stimulation of the fiber by its motor neuron.

Detailed explanation-2: -For a contraction to occur there must first be a stimulation of the muscle in the form of an impulse (action potential) from a motor neuron (nerve that connects to muscle).

Detailed explanation-3: -The release of calcium ions initiates muscle contractions.

Detailed explanation-4: -Calcium then binds to troponin as described above, initiating the contraction process.

Detailed explanation-5: -Depolarisation and calcium ion release. Actin and myosin cross-bridge formation. Sliding mechanism of actin and myosin filaments. Sarcomere shortening (muscle contraction)

There is 1 question to complete.