1. The Nervous System
Lesson objective – to be able to explain how an electrical impulse can pass from one nerve to another

2. Success Criteria
All students can describe in outline how the nervous system is coordinated by the brain
Most students can explain how a simple reflex arc takes place and give some examples
Some students can explain how a synapse works

3. WALT: to revise homeostasis
WILF
All will be able to describe how the nervous system and hormones contribute to homeostasis
Most will be able to explain how a reflex arc works and how it protects the body
Some will be able to explain in detail how the menstrual cycle is controlled by the hormones of the pituitary and ovaries.

4. What do neurones look like?
dendrites
myelin sheath
cell body
axon

5. What are sensory neurones?
Sensory neurones transmit messages from sense receptors, such as the eye or nose, to the brain or spinal cord.
cell body
nerve impulse from sense organ
nerve impulse to CNS

6. What are motor neurones?
Motor neurones transmit messages from the brain and spinal cord to the muscles and glands.
cell body
muscle

7. Reflex and Voluntary Actions
Response to stimuli can be voluntary and involuntary
Voluntary actions require thought
Give two examples –
Reflex actions are a rapid involuntary response to a stimulus
Give two examples -

8. A reflex arc Teacher notes
This five-stage sequence illustrates the electrical pathway of the knee-jerk reflex. Suitable prompts could include:
What are the cells that respond to stimuli called?
Where do sensory neurones take the message to?
What are the nerves in the spinal cord called and what job do they do?
Which tissues will respond to the message that travels down the motor neurone?
Why isn't the brain consulted before the reflex action starts?

9. The Reflex Arc This is the response. Extremely fast
Stimulus is the hot flame
Detected by the temperature receptor in the skin
Sensory neurone transmits impulse to the spinal cord across the synapse to the relay neurone
Impulse crosses synapse to motor neurone and is transmitted to motor end plate
Muscle in the arm is the effector and contracts
This is the response.

10. What is a synapse?
A synapse is a junction between two neurones across which electrical signals pass. The human body contains up to 500 trillion synapses.
presynaptic cell
postsynaptic cell

11. The release of neurotransmitters
When a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles.
synaptic vesicle
neurotransmitter molecules

12. Continuing the impulse
The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse.
synaptic cleft
nerve impulse
receptor

14. There is a tiny gap between 2 neurones called a synapse.
A chemical transmitter diffuses across the gap.
It triggers receptors on the next neurone which cause an electrical impulse to be produced.
Synapses mean that impulses can only travel in one direction.

15. True or false? Teacher notes
This true-or-false activity could be used as a plenary or revision exercise on the nervous system, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.