How did Christopher Reeves heart and intestines work if he had a severed spinal cord?

Answer 1

This is a common question when discussing people with spinal cord injuries. The answer is that the heart and gastrointestinal tract are two examples of organs that can function without any input from the brain. The heart has a built-in "pacemaker" called the SA node, that initiates every heart beat. Similarly, the gastrointestinal system has its own nervous system, called the enteric nervous system, that regulates many of its functions (eg: peristalsis). The enteric nervous system controls many reflex activities (eg: contraction behind contents and relaxation in front of contents) that are mediated almost entirely by the spinal cord without any influence from the brain.

So, does the brain have any role in heart or gastrointestinal function? The answer to this is yes! For the most part, the brain and brainstem assist us in controlling more complex functions of these organs, such as fine-tuning of their functions. For example, to keep the heart rate at a level congruent with activity and/or blood carbon dioxide levels, or for starting peristalsis at the mere sight or smell of food. As such, although people with spinal injuries dont lose total function of organs like the heart and gastrointestinal tract, they often suffer from many diseaes associated with these organs, because their ability to regulate the complex or fine-tuning mechanisms are interupted.