Involuntary muscles are controled by the brain without thinking about them.

Our heart is an involuntary muscle. The muscles in our organs and blood vessels are also involuntary. Some muscles are both voluntary and involuntary. The muscles that control breathing are an example. We can think about breathing and change the speed or depth of our breathing. But when we stop thinking about it, we keep breathing anyway.

Some muscles that are involutary can be controlled with a lot of practice. Scientists have experimented with this type of control. People can sometimes concentrate and open up blood vessels in their hands and other extrimities. This increases the flow^* of blood into these areas and reduces the flow of blood into the brain. This reduced pressure^* in the head might relieve some severe types of headaches.