The Muscular System

The muscular system makes up nearly half the weight of the human body, this is why when we train we sometimes put on weight instead of losing it. We put on muscle weight.

The muscles provide the forces that enable the body to move. Muscles stretch across joints to link one bone with another and work in groups to respond to nerve impulses.

There are three types of muscle:

Skeletal muscle

• There are nearly 650 skeletal muscles in the human body!
• Skeletal muscles are attached to the skeleton
• They work in pairs: one muscle moves the bone in one direction and the other moves it back again
• Skeletal muscles are voluntary muscles – in other words we think about what movements we want to make (at least, usually!) and send messages via our nervous system to tell the appropriate muscle(s) to contract.
• Muscle contractions can be short, single contractions or longer ones.

Smooth muscle

• Smooth muscle is found in our internal organs: in our digestive system, our blood vessels, our bladder, our respiratory organs and, in a female, the uterus.
• Smooth muscle can stretch and maintain tension over extended periods
• Smooth muscles are involuntary muscles – in other words we do not have to think about contracting them because they are controlled automatically by the nervous system.
• It would be pretty inconvenient if we had to think about digesting our food, for example!

Cardiac muscle

• As the name should tell you, cardiac muscle is found only in the heart.
• It can stretch, just like smooth muscle, and contract like skeletal muscle.
• It is a twitch muscle – it only does short single contractions
• Like smooth muscle, cardiac muscle is involuntary. It’d be rather dangerous if it were voluntary – we could stop our heart beating any time we wanted!