Back in the nervous system webpages (on the brain), you learned about the respiratory center found in the medulla and pons. Remember? The medulla contains the main region for respiration-- the region responsible for causing the normal, resting inspiration. This region is called the dorsal respiratory group. If you think about it, the most basic need in respiration to merely survive is the ability to inhale a normal breath. Once inspiration has occurred, expiration can happen passively. In this manner, we can obtain our tidal volume of air simply by getting inspiration to occur.
The dorsal respiratory group cycles through activity. When active, its neurons are firing in bursts that cause the contraction of inspiratory musculature. When it stops being active, those muscles can relax, and expiration occurs.
The ventral respiratory group is only active when you need to breathe more actively. For example, when you are talking and forcing air out, you are using your ventral respiratory group. Forced expiration requires the ventral respiratory group. Your book tells you that the term "medullary rhythmicity area" is used to describe the dorsal and ventral respiratory groups; I don't care if you know that one term, just that you do know the dorsal and ventral respiratory groups and what they do.
Another important area of the respiratory center is the pneumotaxic area. This area is in the pons and is important for regulating the amount of air one takes in with each breath. You see, if you could examine the activity of the dorsal respiratory group in total isolation, you would see that its rhythmic bursts of activity are of constant duration and at a constant interval. But you know that we don't breathe that way; we don't have a totally steady breathing rate-- it is always adjusting to our situation. Yet, the inspiratory musculature is controlled by the dorsal respiratory group. So, this is where the pneumotaxic area comes into play. The pneumotaxic area alters the bursting pattern of the dorsal respiratory group. When we find ourselves needing to breath faster, the pneumotaxic area tells the dorsal respiratory group to speed it up. And when we need to take longer breaths, the pneumotaxic area tells the dorsal respiratory group to prolong its bursts. All the information from the body that needs to feed into the control of our breathing converges in the pneumotaxic area, so that it can properly adjust our breathing.
Minute by minute we have to be able to alter the amount of air we breathe. For example, if I get up and walk across the room, I need to get more than my tidal volume of air. If I continue to move around by exercising for a while, I need a lot more air. Then, when I return into a resting state (not even moving my fingers on the keyboard!), less air is needed again. How can we control how much air we need all the time? (In other words, what tells the pneumotaxic area what it needs to tell the dorsal respiratory group?)
© 2011 STCC Foundation Press