The Senses and Nervous System

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