ch8 Control of Breathing notes

ch8 Control of Breathing notes - Control of Breathing...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Control of Breathing Questions 1. What is controlled by breathing? 2. Is control automatic? 3. Where are the sensors located? Starting with a functional view, the most important thing regulated by breathing is PCO2 of arterial blood. In normal humans arterial PCO2 is maintained at 40 mm Hg. The engineering style control system block diagram involved is shown below. Unlike a man made control system, there is no design documentation so matching this diagram to the more anatomical pictures shown later is not always obvious. Looking at the picture showing where the main neurons (respiratory groups) controlling breathing are located(medulla) makes it obvious that other brain areas (cortex, hypothalamus, and cerebellum) can easily be involved. There is an automatic feature to breathing as well as a learned part. Just as humans must learn to walk, correct breathing must be learned as well. Quiet breathing at rest or sleep is mainly automatic, while breathing during exercise is learned(neurally mediated). The result is that most athletes during moderate exercise can maintain arterial PCO2 and PO2 absolutely constant at the normal level. A more detailed picture of the key neuronal pools and muscles involved is shown below. The muscles of breathing are skeleta muscles which share most characteristics with muscles in the rest of the body. The main difference is that especially the diaphragm never rests. Why the diapjhragm never seems to fatigue like other skeletal muscles in a normal person is an interesting question. One possibility is that it adapts to the continuous use. This is supported by the difficulty in weaning patients off a mechanical respirator who have been artificially ventilated for long periods. Another comment connected with the picture below is that it is based primarily on experiments in cats so there is always some uncertainty on relevance to man. There is one difference that is known . In most animals, there is a reflex called the Hering-
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Breuer reflex where a normal resting breath is terminated due to feedback from lung stretch receptors. These receptors are located in the lungs and have sensory nerve fibers which pass in a nerve bundle called the vagus nerve and have connections to the medullary neurons. When this nerve is severed in an animal, very deep and slow breathing rate results.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 8

ch8 Control of Breathing notes - Control of Breathing...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online