How is breathing involuntary if the muscles that control it are skeletal? Breathing is involuntary. However, the muscles that control it are skeletal: intercostal muscles and the diaphragm. Are there other muscles involved? Is it that these skeletal muscles are being controlled and/or acting involuntarily?

Humans can both continue to breathe while asleep, and they can also intentionally take a deep breath.

How is breathing be an involuntary act, that can also be controlled?

  • $\begingroup$ There are other such muscles on "autopilot". Blinking is both voluntary and involuntary. $\endgroup$ – anongoodnurse Mar 4 '19 at 4:39

Breathing is controlled by both the Autonomic nervous system and the voluntary nervous system. You see this in instances where our breath rate increases in flight or fight situations glide to the secretion of Adrenaline and also when we intentionally increase the breathing rate when undergoing high levels of activity. This is due to the fact that the involuntary aspect of breathing is controlled by the medulla oblongata and the voluntary aspect s controlled by the cerebral cortex. The fact that it is controlled by skeletal muscles has nothing to do with how it is innervated. For example, Cardiac muscles are innervated by both the hearts own conducting system and by the Autonomic nervous system. If you're wondering why the skeletal muscles dont get fatigued, it's because there is a small but significant rest period between each Breathing cycle (inhalation and exhalation). Therefore the skeletal muscles have a rest period. However if a high rate of breathing does occur for a sustained period, they will fatigue and that's why you get cramps after a marathon or a sprint.

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    $\begingroup$ Nice answer! Welcome. :) $\endgroup$ – anongoodnurse Mar 4 '19 at 4:32

I would argue that the problem here is more semantic than biological. We artificially classify processes into "voluntary" and "involuntary", but the reality is much more complicated. For example, is walking voluntary or involuntary? Well, if I decide to go walking, it may initially be voluntarily, but when I am walking, I am doing very little in the way of thinking about walking. Breathing is much the same way. There is BOTH a degree of conscious control from the cortex, and a basal regulatory system in the brain stem that keeps things going below conscious perception. Another way to look at this is that the conscious control from the cortex modulates the medulla based breathing system.

  • $\begingroup$ This could be a better answer without the (unrelated imo) philosophizing. "Involuntary breathing" is not semantic. We do it whether we want to or not; the brain will not allow us to forgo that activity. That makes it involuntary, and under the control of the ANS. There are also nerves in the CNS -> diaphragm that allow voluntary control, which can override the ANS to a point, but in the end, it's involuntary. Not semantics at all. $\endgroup$ – anongoodnurse Mar 4 '19 at 4:37

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