1. Neurons and synaptic transmission
Pages
Biopsychology
Specification details
The structure and function of sensory, relay and motor neurons.
The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition.
5 minutes

2. Key assumptions of biopsychologists
Biopsychologists assume that behaviour and experiences are caused by activity in the nervous system
The nervous system transmits signals for communication via the billions of nerve cells (neurons) it houses
These nerve cells communicate with each other, through electrical and chemical messages, within the body and the brain.

3. Neurons Cells that conduct nerve impulses are called neurons
The things that people think and feel, say and do are caused, one way or another, by electrochemical events occurring within and between the neurons that make up the nervous system, particularly those in the brain (80%)

4. Three types of neurons
Relay Neuron

5. Write one sentence about what the following features do
Nucleus the control centre of a cell, which contains the cell's chromosomal DNA Dendrite Receives the nerve impulse or signal from adjacent neurons Axon Where the electrical signals pass along. Myelin sheath Insulates /protects the axon from external influences that might effect the transmission of the nerve impulse down the axon. Nodes of ranvier These speed up the transmission of the impulse by forcing it to ‘jump’ Terminal buttons Terminal buttons send signals to an adjacent cell.

6. Different types of neurons
The cellular structure of all neurons is the same. There are anatomical differences in size, depending on their function
1. Motor neuron
2. Relay (Interconnecting) neuron
3. Sensory neuron
Function
Carries messages from the CNS to effectors such as muscles and glands
Transfers messages from sensory neurons to other interconnecting neurons or motor neurons
Carries messages from the PNS to the brain and spinal cord
Length of fibres
Short dendrites and long axons
Short dendrites and short or long axons
Long dendrites and short axons
Structural and functional differences

7. MOTOR RELAY SENSORY

8. Relay neuron

10. The knee-jerk reflex
In a reflex arc, like the knee-jerk reflex, a stimulus, such as a hammer hitting the knee, is detected by sense organs in the peripheral nervous system, which conveys a message along a sensory neuron. The message reaches the central nervous system where it connects with a relay neuron. This then transfers the message to a motor neuron. This then carries the message to an effector such as a muscle, which causes the muscle to contract and, hence, the knee to move or jerk.

11. Synapse between two neurons.
Synaptic tramsmission

12. Neurotransmitters…
…are chemicals that are released from a synaptic vesicle into the synapse by neurons.
They affect the transfer of an impulse to another nerve or muscle
These neurotransmitters are “taken back up” into the terminal buttons of neurons through the process of reuptake
Or they are broken down by an enzyme

13. How a synapse works
A synapse

14. Action Potential
An action potential occurs when a neuron sends information down an axon, away from the cell body. The action potential is an explosion of electrical activity - this means that some event (a stimulus) causes the resting potential to move forward

15. Excitation and inhibition
Synaptic connections can be excitatory or inhibitory – the difference lies in the action of the neurotransmitter at the postsynaptic receptor
Excitatory - they make it more likely the next neuron will fire (such as acetylcholine)
Inhibitory - they make it less likely the next neuron will fire (such as GABA)
Normal brain function depends upon a regulated balance between excitatory and inhibitory influences
Analogy of the pedals in a car – excitatory = accelerator and inhibitory = brake

16. Synaptic transmission
Sort the cards into the correct order and then write the details up on the flow diagram to show the process of synaptic transmission

17. Synaptic transmission - answers
nerve impulse travels down an axon
nerve impulse reaches synaptic terminal
this triggers the release of neurotransmitters
the neurotransmitters are fired into the synaptic gap
neurotransmitter binds with receptors on the dendrite of the adjacent neuron
if successfully transmitted the neurotransmitter is taken up by the post-synaptic neuron
the message will continue to be passed in this way via electrical impulses

18. Synapse: The gap between the end of one neuron and the dendrites of the next neuron.
What you need to label:
Direction of impulse.
Axon terminal
Synaptic vesicles containing neurotransmitter
Synaptic gap
Dendrite
Receptor site

19. Can you?
Explain what is meant by sensory, relay and motor neurons (2 marks each)
With reference to neurotransmitters, explain what is meant by both excitation and inhibition (4 marks)
With reference to sensory, relay and motor neurons, explain the knee-jerk reflex (4 marks)
Explain the difference between excitatory or inhibitory synaptic connections (4 marks)
Answer the ‘Check it’ questions on page 117

20. Essay
Outline and evaluate the role of biological structures in explaining human behaviours (12 marks)

21. Ensure you have written up your class notes to include the following:
Homework
Ensure you have written up your class notes to include the following:
The structure and function of sensory, relay and motor neurons.
The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition.