Which is a correct description of the role of calcium ions in the neuromuscular system?
Correct answer: B. Moved in by diffusion through gated ion channels in pre-synaptic membranes of excitatory neurones causing vesicles to move to pre-synaptic 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. Moved in by diffusion through gated ion channels in pre-synaptic membranes of excitatory neurones causing vesicles to move to pre-synaptic membrane as an impulse arrives.
- C. Exchanged with chloride ions at the post-synaptic membrane, in changing membrane potential in inhibitory neurones.
- D. Actively pumped out of axons at nodes of Ranvier of myelinated neurones, being the main cause of the potential difference that is maintained during the resting potential.
Explanation
The arrival of an impulse at the synaptic knob causes gated Ca2+ channels in the presynaptic membrane to open. Ca2+ rush into the cytoplasm of the presynaptic neurone from the synaptic cleft. The influx of Ca2+ causes vesides with neurotransmitters to move to the presynaptic membrane and fuse with it, emptying their contents into the synaptic cleft by exocytosis.
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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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