Identify one factor that can cause the first sodium channel to open in a muscle cell.

SKELETAL MUSCLE

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

A	Calcium ions being released from the sarcoplasmic reticulum.
B	Acetylcholine being released from the motor neuron
C	Calcium ions binding to troponin
D	ATP causing the myosin heads to pop up.

Explanation:

Detailed explanation-1: -(A) Neurotransmitter (acetylcholine, ACh) released from nerve endings binds to receptors (AChRs) on the muscle surface. The ensuing depolarization causes sodium channels to open, which elicits an action potential that propagates along the cell.

Detailed explanation-2: -The acetylcholine binds to the nicotinic receptors concentrated on the motor end plate, a specialized area of the muscle fibre’s post-synaptic membrane. This binding causes the nicotinic receptor channels to open and let sodium ions enter the muscle fibre.

Detailed explanation-3: -For example, when acetylcholine is released at the synapse between a nerve and muscle (called the neuromuscular junction) by a presynaptic neuron, it causes postsynaptic Na+ channels to open.

Detailed explanation-4: -The release of acetylcholine occurs when an action potential is relayed and reaches the axon terminus in which depolarization causes voltage-gated calcium channels to open and conduct an influx of calcium, which will allow the vesicles containing acetylcholine for release into the synaptic cleft.

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