How do people paralysed from the neck down still retain the ability to breathe, pump blood, metabolise food etc., even though their muscles are paralysed?
In: Biology
>It depends on the level of paralysis. The diaphragm is innervated by the ventral roots of the cervical roots from C3/C4/C5, so lesions at or above those levels may indeed result in loss of diaphragm function, and thus require mechanical ventilators to breathe.
>The heart functions fairly autonomously (since its contractions are mediated by the SA node), and is thus able to beat independent of spinal influences. However, there are a number of parasympathetic and sympathetic inputs to the heartbeat, such that damage to the vagus nerve (unlikely in a purely spinal lesion, since the vagus nerve is a cranial nerve) may result in tachycardia, and damage to the sympathetic ganglia may result in inability to modulate inotropy.
>Digestion is similarly largely governed by neurons of the enteric nervous system, which function fairly independently of higher-order inputs. There is some parasympathetic and sympathetic signal to the gut, which may indeed affect digestion, but my understanding is that those factors aren’t as important as the native enteric nervous system.
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