When they remove the heart for surgery, do they have to cut a lot of nerves?
How are those repaired?
I would assume that the only time the heart is actually removed is when the patient is receiving a transplant, and so that would probably be the only time that any nerves would have to be cut.
They aren’t. From this site:
“In a heart transplant, these nerve connections do not reconnect for an extended period of time, if at all; however, the transplanted heart is able to function in its new host through the capacity of its intact, intrinsic nervous system.”
Thats very interesting. But how is blood pressure and pulse rate regulated? Do people who had transplant need a pacer for that job?
I mean, how does the heart know that it’s time to speed up or speed down?
Since it doesn’t receive an external signal from the brain, it won’t speed up when the patient is running or speed down when he’s sleeping.
Well, according to this site:
IANAD, but I would venture to guess that pulse regulation can be achieved by the use of hormones (such as adrenaline) alone, without having the vagus nerve connected. I also managed to find this article, which mentions the effects of hormones on decreasing the heart rate:
Notice that ANP augments the action of the vagus nerve. That would indicate that it can affect a change in heart rate on its own, even though the effect wouldn’t be as pronounced.