Which is a correct description of the role of calcium ions in the neuromuscular system?
Correct answer: B. Diffuses through gated ion channels in presynaptic membranes of excitatory neurons, prompting vesicles to move to the presynaptic membrane as an impulse arrives
- A. Exchanged with sodium ions through co-transport channels at axon surfaces during the reestablishment of a resting potential after an action potential
- B. Diffuses through gated ion channels in presynaptic membranes of excitatory neurons, prompting vesicles to move to the presynaptic membrane as an impulse arrives
- C. Exchanged with chloride ions at the postsynaptic membrane, altering membrane potential in inhibitory neurons
- D. Actively pumped out of axons at nodes of Ranvier in myelinated neurons, which is the main cause of the potential difference that is maintained during the resting potential
Explanation
The role of calcium ions in the neuromuscular system is crucial during synaptic transmission. When an action potential reaches the synaptic knob, it triggers the opening of voltage-gated Ca2+ channels in the presynaptic membrane. Calcium ions then diffuse into the neuron, causing synaptic vesicles filled with neurotransmitters to move towards and fuse with the presynaptic membrane, leading to neurotransmitter release into the synaptic cleft by exocytosis. This process does not involve sodium or chloride ions, nor does it relate to the maintenance of resting potentials, which are handled by different ion channels and pumps.
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Coordination depends on receptors, neurons, synapses and nerve impulses, with reflex actions traced through the reflex arc and the roles of major brain regions. Chemical coordination covers endocrine glands and hormones, including how hormones regulate growth, metabolism, reproduction and internal balance, unlike rapid nervous control.
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