Transcript The Senses and Nervous System

The Senses and Nervous System
Chapter 9
The Senses
• The 5 senses are:
Sight, Hearing Touch Taste and Smell.
• The 5 sense organs are:
Eye, Ear, Skin, Tongue and the Nose
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.
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.
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.
The Eye
• Lens-focuses light on
the retina.
• Iris-controls the light
entering the eye
• Ciliary musclechanges the shape of
the lens.
• Retina- contains the
light sensitive cells.
• Optic nerve-carries
messages back to the
brain.
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.
Long and short sight