Voluntary actions

The idea

Voluntary actions are based on deciding what to do next; for these the brain sends messages to the muscles.

A clap at the end

At the end of a school programme, Arjun decides to clap. His hands start to move.

What do you think is the first step behind Arjun's clapping?

• He decides what to do next
• A flame touches his hand
• A reflex arc in his spinal cord acts alone

Decided or not

Sort each action into the right group.

Decide, then move

In a voluntary action the brain does the deciding. Then it must send messages to the muscles. The book calls this the second way in which the nervous system communicates with the muscles. The first way is the reflex arc.

Voluntary actions are based on deciding what to do next. For these the brain sends messages to the muscles.

Notes

Voluntary actions are based on deciding what to do next; for these the brain sends messages to the muscles, as when we write, talk, move a chair or clap.

Check yourself

What are voluntary actions based on?

In a voluntary action, what does the brain do after the decision?

Which is a voluntary action?

• A sudden change in the environment alone. That describes a reflex action. Voluntary actions are based on deciding what to do next.
• Hormones from the adrenal glands. Voluntary actions are based on deciding what to do next, with the brain sending messages to the muscles.
• Deciding what to do next — correct. Yes!
• It sends messages to the muscles — correct. Yes!
• It waits for the spinal cord to act alone. The brain itself sends messages to the muscles in a voluntary action.
• It releases chemicals into the blood. In a voluntary action the brain sends messages to the muscles.
• Change in the size of the pupil. The book gives this as a simple reflex action.
• Moving a chair — correct. Yes!
• Pulling the hand back from a flame. This is a reflex action, done without thinking.