1. The nervous system

2. Main Function: The Nervous System
This communication system controls and coordinates functions throughout the body and responds to internal and external stimuli.
Our nervous system allows us to feel pain.

3. 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.

4. 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.

5. 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

6. The Nerve
A nerve is an organ containing a bundle of nerve cells called neurons.
Neurons carry electrical messages called impulses throughout the body.
Picture shows hundreds of severed neuron axons

7. Basic nerve cell structure

8. 3 main types of nerve cells
sensory neurone
relay neurone
motor neurone

9. Because neurons never touch, chemical signalers called neurotransmitters must travel through the space called synapse between two neurons.
Neurotransmitters
(pink
spheres)
The message is transferred when RECEPTORS receive neurotrans-mitters.
Synapse (gap)

10. Parts of a Neuron
Cell body: contains nucleus & most of the cytoplasm
Dendrites: projections that bring impulses into the neuron to the cell body.
Axon: long projection that carries impulses away from cell body 1 3 2

11. Sensory Neuron Interneuron Types of Neurons Synapse Synapse
Motor Neuron
Interneuron
Synapse
Muscle Contracts
Motor Neuron
Sensory Neuron

12. Where can the largest cells in the world be found?
Sensory Neuron
carry impulses from sense organs to spinal cord & brain
Fun Fact:
Where can the largest cells in the world be found?
The giraffe’s sensory and motor neurons! Some must bring impulses from the bottom of their legs to their spinal cord several meters away!!

13. Interneuron processes impulses in brain and spinal cord
- connect sensory and motor neurons

14. carry impulses from the brain & spinal cord to muscles & glands
Motor Neurons
carry impulses from the brain & spinal cord to muscles & glands
Axon End
Axons branching out to muscle fibers

15. Communication with Neurons
Nerves work together with muscles for movement. An impulse begins when one neuron is stimulated by another neuron or by the sense organs.
The impulse travels down the axons of Sensory neurons to the brain cells called Interneurons.
The brain will then send an impulse through motor neurons to the necessary muscle or organs, telling it to contract.

16. 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.

17. 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.

18. The knee jerk reflex action
Sometimes
called a
relay or
Connector
neurone

19. Another reflex action

20. 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)

21. Response
Stimulus
Receptor
Effector
Motor neurone
Sensory neurone
Central
Nervous
system

22. Examples of responses Voluntary actions Eating a cake Riding a bicycle
Walking
Playing the piano
Coming to school
Involuntary actions
Your heart beat
Breathing
Blinking
Removing hand from hot object
Choking
Salivating