1. The Senses and Nervous System
Chapter 9

2. The Senses The 5 senses are: Sight, Hearing Touch Taste and Smell.
The 5 sense organs are:
Eye, Ear, Skin, Tongue and the Nose

3. The Nervous System The nervous system consists of:
the brain and spinal cord (the central nervous system), and the nerves that run out from the spinal cord to all parts of the body.

4. Nerves
Large nerves are made up of bundles of nerve cells called neurons.
Each nerve cell has a long fibre which could be up to a meter long.

5. Sensory and Motor Nerves
Sensory nerves carry messages to the brain. (eye to brain)
Motor nerves carry messages from the brain.(brain to muscle)
In a reflex action the brain is not involved. The message goes along the sensory nerve to the spinal cord. From there the message is sent along the motor nerve to the muscle.

6. The Eye Lens-focuses light on the retina.
Iris-controls the light entering the eye
Ciliary muscle-changes the shape of the lens.
Retina- contains the light sensitive cells.
Optic nerve-carries messages back to the brain.

7. The Iris and Pupil
In bright light the Iris closes to make the pupil small.
In dim light, the iris opens to make the pupil large to allow in more light.

8. Long and short sight