The spinal cord
The nerves (neurones)
The central nervous system (or CNS for short) is made up of the brain and the spinal cord.
What is the job of the nervous system?
Our survival depends on us being sensitive to our surroundings. We need to be able to detect any changes and be able to respond to them.
The sense organs are:
These organs sense:
Sound and balance
Pressure, pain, temperature
How does our nervous system work then?
Our sense organs contain special receptor cells which will detect a change in our surroundings (a stimulus)
The receptor cells will change the stimulus into an electrical impulse which is passed along nerve cells
The message will usually go to the brain which will then process it
The brain then sends a message along nerves to an effector organ (usually a muscle or a gland)
The effector organ will then give a response (e.g. a muscle will move, or a gland will produce a hormone)
When a nerve ending meets up with another nerve ending we get a microscopic space
This space is called a synapse
The electrical message travelling along a nerve has to cross the synapse as a chemical message
When the chemical (neurotransmitter) reaches the other nerve ending it causes an electrical impulse to travel along the next nerve cell
Sometimes a stimulus requires an immediate response. This is called a reflex action. It is an involuntary response and we do it without thinking. These automatic responses do not have to be learned. They can be very important in preventing injury to ourselves.