How come there are some automated body functions that we can “override” and others that we can’t?

Question

For example, we can will ourselves breathe/blink faster, or choose to hold our breath. But at the same time, we can’t will a faster or slower heart rate or digestion when it might be advantageous to do so. What is the difference in the muscles involved or brain regions associated with these automated functions?

In: Biology

Answer 1

The heart and the intestines have a type of muscle called cardiac and smooth muscle respectively. These muscles are not innervated by nerves that can be voluntarily controlled by the brain.

Breathing and blinking fuctions are controlled by skeletal muscles (like your arms or legs) which are innervated by nerves that can be voluntarily controlled.

Extra info for the curious: blood vessels also have smooth muscle cells that control the width of your vessels to adjust your blood pressure. These are all innervated by the sympathic nerves (unvoluntary control).

You have probably heard of the fight or flight response. They use the sympathic innervations to STOP your gut fonctions (because they are useless in a life or death situation) and INCREASE heart rate and blood pressure.

Edit: clarification and typo

Edit2: yes my bad, the heart is actually made of cardiac muscle like people are mentionning, had a brain fart last night. But the sympathic innervation remains the same.