The nervous system & sensitivity

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Slide 1

The nervous system

Slide 2

What is the nervous system made up of?

The brain

The spinal cord

The nerves (neurones)

The central nervous system (or CNS for short) is made up of the brain and the spinal cord.

Slide 3

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.

Slide 4

What are our sense organs?

The sense organs are:

The eyes

The ears

The nose

Tongue

skin

These organs sense:

Light

Sound and balance

Smell

Taste

Pressure, pain, temperature

Slide 5

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)

Slide 6

Stimulus

Receptor

Sensory neurone

Central

Nervous

system

Motor neurone

Effector

Response

Slide 7

Synapses

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

Slide 8

Reacting without thinking

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.

Slide 9

A reflex arc

The nerve pathway taken in a reflex action is called a reflex arc. The nervous message goes to the spinal cord, then a message passes from the spinal cord directly to an effector to give an immediate response.