Klarinet Archive - Posting 000576.txt from 1999/04

From: "Diane Karius, Ph.D." <dikarius@-----.edu>
Subj: Re: [kl] hiccups
Date: Mon, 12 Apr 1999 22:02:22 -0400

> Okay, we have my surgeon friend who plays bassoon in my quintet, who says
> the diaphram is totally involuntary and cannot be controlled no matter how
> much one may think he is able to do this AND then there is George who says
> the opposite. SO, will Dr. Goldman please address this question and give
> his opinion?

I"ll pop in on this one since I am a respiratory
neurophysiologist by trade (studying the neural mechanisms of
breathing) - simply put, George is right.

For more detail: the diaphragm is skeletal muscle
and is inervated by the phrenic nerve. The phrenic nerve receives
input (telling it to fire) from respiratory centers in the medulla
(responding primarily to carbon dioxide, oxygen, and pH of the blood)
as well as from centers in the cortex (voluntary breathing,
breath-holding etc...). We routinely voluntary control/modify our
breathing when we talk, play clarinet etc... (holding your breath,
etc.... are all voluntary actions). However, the existence of the
medullary respiratory centers puts limits on how far we can take this
- we can hold our breaths for quite a long period of time, but
eventually the carbon dioxide & oxygen levels will change to the
point that the respiratory centers will "make" us take a breath.
This is somewhat simplified, but correct as far as it goes.

The mechanism for hiccups is not clear. We do know that hiccups
represent an activation of the diaphragm via the phrenic nerve, but
it is not coming from the respiratory centers (there are lots of
inputs to the phrenic - this is not surprising). It may actually
represent an increase in the excitabiltiy of the phrenic motoneurons
themselves (for the scientifically minded - I'm talking about
bistability of the membrane potential). Beyond that, we don't know
much.
Diane R. Karius, Ph.D.
Department of Physiology
University of Health Sciences
1750 Independence Ave.
Kansas City, MO 641o6-1453
email: dikarius@-----.EDU

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