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Complete this table
SENSE
SENSORY ORGAN /RECEPTORS
SIGHT
Cells in the Retina of the
eye
HEARING
Hairs in the cochlea of the
ear
TOUCH
SMELL
TASTE
STIMULUS
Pressure,
temperature
Smell receptors in the nose Chemicals in the air
Chemicals in food
RECEPTORS
RECEPTORS
Receptor cells contain a nucleus and cytoplasm and
are surrounded by a cell membrane.
Receptors detect a change in the
environment: A STIMULUS
Examples of STIMULI
• Light/dark
• Noise
• Temperature change
• Physical pressure
• Food flavours
• Scents and odours
RESPONSE PATHWAY
STIMULUS
RECEPTORS
RECEPTORS:
EYES, SKIN etc.
CNS
EFFECTORS: Muscles or glands
RESPONSE
THE NERVOUS SYSTEM
The route impulses take
REFLEX ARC
Sensory
neurone
Relay
neurones
(in spinal
cord)
Effectors –
Motor neurone
1. SENSORY
NEURON:
Connects
sensory organs
(e.g. The eyes)
to the CNS.
2. RELAY
NEURON:
By-passes
CNS and
connects a
sensory
organ directly
to an effector
muscle.
3. MOTOR
NEURON:
Connects the CNS
to an effector
muscle/gland (e.g.
The muscles in the
iris of the eye that
control pupil
dilation)
Reflexes??
• Knee jerk Reflex.
Helps balance.
• Gag reflex. When an
object touches the
back of your throat,
it prevents you
swallowing it.
• Pupil reflex. Stops
bright light
damaging the pupil.
NEWBORN REFLEXES
•
•
•
•
•
Walking Reflex
Startle Reflex
Rooting Reflex
Sucking Reflex
Grasp Reflex
STARTER QUESTION: Why do our pupils
change size in different light levels?
REFLEX ARC:
When the Stimulus is light
1. RECEPTOR. E.g. The eye
2. CO ORDINATOR. E.g. The brain
3. EFFECTOR. E.g. The muscles in
the iris of the eye.
THE SYNAPSE
What is a synapse?
• A synapse is the “gap” between
the axon of one nerve and the
dendrite of the next one.
• The average neuron has 1,000
synapses with other neurons.
TEXT BOOK TASKS
• Pages 20-21
• Answer questions 1-6.
• Answer the science skills
questions.