Involuntary Muscles
Involuntary muscles are exaclty that, they make up alot of our muscular control responding to signals from our nerves or brain.
Do we have many involuntary muscles.
Life without involuntary muscles would be impossible. Involuntary muscles control everything from breathing to blinking, so without them sleep would be impossible!
How do they respond.
Of course we control the vast majority of our muscles, so they only respond when we want them to to throw a ball, drive a car, type a letter. But whether they are voluntary or involuntary, all of them respond to signals from the nerves or the brain.
What happens when we recieve a signal.
When this signal is received, tiny microscopic fibres in the muscle cells compress by sliding in past each other, contracting relaxing back to their original size.
In order to do this they must be adequately fuelled, getting their energy from the food and drink you consume. Because the muscles can only hold a limited supply of fuel, your body must store fuel elsewhere in the body either as glycogen (sugar) in the liver, or else as fat.
The need for fuel.
In times when our fuel supply is limited (famine, or even during a long race such as a marathon or triathlon), your body prioritises the use of fuel, so that even when you reach a point of exhaustion, and can no longer keep running, your heart keeps pumping and your diaphragm keep pushing your lungs.
