Light, sound, touch, pressure, chemical or
a change in position or temperature
Five different sense organs eyes, ears, nose, tongue and skin
contain different receptors. Receptors are
groups of cells which are sensitive to a
stimulus. They change stimulus energy
(light energy) into electrical impulses
Sense organs and receptors dont get them
mixed up: The eye is a sense organ - it
contains light receptors. The ear is a sense
organ it contains sound receptors
The five sense organs and the receptors that each contains:
Eyes
Light receptors - sensitive to
light. These cells have a
nucleus, cytoplasm and cell
membrane (just like animal
cells)
Ears
Sound receptors - sensitive to
sound. Also "balance" receptors -
sensitive to changes in position
Nose
Smell receptors - sensitive to chemical stimuli
Tongue
Taste receptors - sensitive to bitter,
salt, sweet and sour, plus the taste of
savoury things like monosodium
glutamate (MSG) - chemical stimuli
Skin
Sensitive to touch, pressure, pain and temperature change
Neurones
Sensory neurones
The nerve cells that carry signals
as electrical impulses from the
receptors in the sense organs to
the central nervous system
Relay neurones
The nerve cells that carry signals
from sensory neurones to motor
neurones
Motor neurones
The nerve cells that carry signals from the
central nervous system to the effector muscles
or glands
Effectors
Muscles and glands are known
as effectors - they respond in
different ways. Muscles contract
in response to a nervous impulse,
whereas glands secret hormones
The central nervous system coordinates a response
The CNS is where all
the information from the
sense organs is sent and
where reflexes and
actions are coordinated.
This consists of the brain
and spinal cord
Neurones (nerve cells) transmit the
information (as electrical impulses)
very quickly to and from the CNS
Instructions from the CNS are sent
to the effectors (musles and
glands) which respond accordingly