The hot pan

About this video

You touch the handle of a pan that has been on the stove, and before you think "hot!" your hand has already jumped away. Only a moment later does it hurt. This video shows how that can happen.

The nervous system is the body's message network. It senses what is happening inside you and around you, works out what that means, and sends orders to muscles and organs. The brain and spinal cord, which runs down inside the backbone, are the control centre; nerves are the cables that run from them to every part of the body, some carrying messages in from the senses and others carrying orders out to the muscles.

The messages are carried by nerve cells called neurons. A neuron has short branches that pick up signals from other cells and one long thread, the axon, that passes the signal on. The signal is electrical and travels very fast. A human brain has about 86 billion neurons. Different parts of the brain do different jobs: the big wrinkled part on top handles thinking, language and the senses, the cerebellum at the back keeps your balance, and the medulla at the bottom runs your breathing and heartbeat. We use all of our brain; the idea that we use only 10% is a myth.

Back to the pan. The skin sends a signal along a nerve to the spinal cord, and the spinal cord sends an order straight back to a muscle in the arm, which pulls the hand away. The message doesn't wait for the brain to decide. A fast, automatic reaction like this is a reflex. The brain hears about it a moment later, and that is when you feel the pain. This video goes with the lesson Brain and Nerves in Biology Level 1 on Knaph.

Transcript

1. 0:00You touch a hot pan. Your hand jumps away before you even think hot. Only a moment later does it hurt.
2. 0:10Your nervous system senses, works out what it means, and sends orders. The brain and spinal cord are the control centre. Nerves are the cables to every part of you.
3. 0:26The messages are carried by neurons. Short branches pick up a signal, and a long thread passes it on. It is electrical and very fast. Your brain has about 86 billion of them.
4. 0:42Different parts of the brain do different jobs, thinking, balance, breathing. We use all of it. The ten percent idea is a myth.
5. 0:56Back to the pan. The skin signals the spinal cord, and the spinal cord sends an order straight back to the arm. That is a reflex. The brain hears about it later, and that is when it hurts.
6. 1:16For some dangers, the spinal cord answers on its own.