Reflexes
L.O: To know what a reflex is and how
they work
Can you measure your pupil in the
light and dark? Remember don’t
touch your eye!
Can you move your body without
using your brain?
• What is a reflex?
– Reflex action is a rapid automatic and involuntary
response to a stimulus which is not under the control
of the brain.
• Can anyone think of any reflexes?
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Knee-jerk reflex
Achilles reflex
Touching a hot plate
Coughing
yawning
blinking of eyes
Sneezing
movement of diaphragm during breathing
How could you prove that your brain isn’t
coordinating a response?
Nervous system card sort
- Sort the cards into a normal nervous system
response and a reflex response
- Match the example to the sequence
Coordinator:
Relay
neurone
Your brain has no
part in this
pathways ie
reflex arc
How do reflexes work?
• Video
Label your diagram and explain in your own words how a reflex
works, using the words
Stimuli, Receptor, Sensory neuron, Interneuron, spinal cord,
motor neuron, muscle, contracts, reflex action
Explain the reflex
pathway when you
touch a hot tripod
What are the differences between the
motor and sensory neurones?
Sensory
Neurone:
•Takes
messages
from receptors
to the brain or
spinal cord
Motor Neurone:
•Takes
messages from
the brain or
spinal cord to
the muscles
and organs
Neurones join at synapses
• Chemicals are secreted
between the gaps
• Synapses slow down
impulses, but one neurone
can synapse several
• A relay neurone has
synapses with a sensory and
motor neurone and also
those to the brain
How do the following drugs work?
•
•
•
•
Paracetamol
Aspirin
Dentists procaine injected into gums
Curare given to patients undergoing surgery to
stop muscles moving
Plenary
Explain what these words mean
•
•
•
•
•
•
•
•
Stimulus
Receptor
Sensory neurone
Relay neurone
Motor neurone
Effector
Response
Reflex arc
1. Which is the correct sequence for a
nervous response
A – Stimulus, receptor, co-ordinator, response,
effector
B – Receptor, effector, stimulus, co-ordinator,
response
C – Stimulus, Receptor, co-ordinator, effector,
response
D – Stimulus, effector, co-ordinator, receptor,
response
2. Which is the receptor in your eyes?
A – Sound receptor
B – Smell receptor
C – Pressure receptor
D – Light Receptor
3. Which is the neurone which takes
impulses from your receptor to your spinal
cord?
A- Sensory neurone
B – Relay neurone
C – Connector neurone
D - Motor neurone
4. What part of your nervous system is
missed in a quick reflex response?
A – Relay neurone
B – Spinal cord
C – Brain
D - Effector
5. Which of these stimulus is the correct
one for feeling hot water
A – Taste
B – Light
C – Temperature
D - Touch
6. Which one of these is not an effector?
A – Leg muscle
B – Biceps
C - Salivary glands
D – Ear drum
Answers
1. Which is the correct sequence for a
nervous response
A – Stimulus, receptor, co-ordinator, response,
effector
B – Receptor, effector, stimulus, co-ordinator,
response
C – Stimulus, Receptor, co-ordinator, effector,
response
D – Stimulus, effector, co-ordinator, coordiantor, receptor, response
2. Which is the receptor in your eyes?
A – Sound receptor
B – Smell receptor
C – Pressure receptor
D – Light Receptor
3. Which is the neurone which takes
impulses from your receptor to your CNS
A- Sensory neurone
B – Relay neurone
C – Connector neurone
D - Motor neurone
4. What part of your nervous system is
missed in a quick reflex response?
A – Relay neurone
B – Spinal cord
C – Brain
D - Effector
5. Which of this stimulus’s is the correct
one for feeling hot water
A – Taste
B – Light
C – Temperature
D - Touch
6. Which one of these is not an
effector?
A – Leg muscle
B – Biceps
C - Salivary glands
D – Ear drum