How come a paralyzingly spine break shuts down pain/muscle operation, but not organs and other bodily functions?

Question

In the case of a spinal break that causes someone to become paralyzed, why would organs and other bodily functions un-affected if the cause is a separation of the brain’s ability to communicate with the body? Does the brain not also subconsciously control breathing, heart beat, etc?

In: 159

Answer 1

The heart and lungs are innervated (that is: receive nerve signals) from nerves that actually begin above the spine, including the vagus nerve and the glossopharyngeal nerve.

This means that even spinal chord damage done high on the spine is unlikely to stop the heart and lungs.

But it can still make things harder – the muscles around the heart and lungs receive innervation from normal spinal nerves. Thus the diaphragm can be paralysed, making anything but the most shallow breathing very hard and the contractility of the heart can be reduced, again leading to shallow beats, even if the heart rate is normal.

But as you’ve noticed, other organs don’t completely shut down, even after a very high spinal injury.

This is because of the autonomic nervous system.

In essence, most of your organs have their own set of nerves that they use to send signals back and forth and which act independently from thought or signal from the brain.

With this in mind, the kidneys will keep filtering blood, the intestines will continue peristalsis and so on at a sort of baseline level.

What will change is any time that baseline level isn’t enough as well as any point that normally needs somatic (conscious) control.

For example, if you eat a big meal and your stomach stretches, normally it sends a message to the brain saying “get the intestines ready, this is a big one”. But without the spinal cord, this message gets lost and so it can lead to distension (uncomfortable swelling of the intestine) and blockage, so many paraplegics find they need to eat smaller meals and avoid certain foods.

Similar, the bladder can’t send a message saying “I’m full, we need to urinate”, so paraplegics may find themselves urinating unexpectedly or developing distension and UTIs if the bladder doesn’t void itself – sometimes leading to a need for 24/7 catheterization.

Even with the autonomic nervous system doing it’s best, we are often surprised at the number of functions that diminish or stop entirely when the spinal cord is disrupted – it is not a fun injury.