1. NS cells and neurotransmitters at synapses
KA 3: The cells of the nervous system and neurotransmitters at synapses
(a) Structure and function of neurones
(e) Mode of action of recreational drugs
NS cells and neurotransmitters at synapses
(d) Neurotransmitters, mood and behaviour
(b) Neurotransmitters at synapses
(c) Function of converging, diverging and reverberating pathways

2. By the end of this section you will be able to …..
State what is meant by a ‘converging’ neural pathway
State what is meant by a ‘diverging’ neural pathway
State what is meant by a ‘reverberating’ neural pathway
Identify the above pathways in a diagram
State what is meant by plasticity of response
State 3 occasions when plasticity of response would occur
Plasticity of response is created when new neural pathways are developed to create new responses, bypass areas of brain damage, to suppress reflexes or responses to sensory impulses.
Converging neural pathways increase the sensitivity to excitatory or inhibitory signals. Diverging neural pathways influence several neurons at the same time.
Reverberating pathway neurones later in the pathway synapse with earlier ones sending the impulse back through the circuit.

3. Complex neural pathways
Neurones are found to be connected to one another in many different combinations in the CNS. This enables the nervous system to carry out many complex functions.
Converging
Diverging
Reverberating

4. Complex neural pathways
Neurones are found to be connected to one another in many different combinations in the CNS. This enables the nervous system to carry out many complex functions.
Converging
Diverging
Reverberating
To ‘converge’ means to come together and meet at a common point.
Impulses from several sources are channelled towards and meet at one point. This increases the sensitivity to excitatory or inhibitory signals.
To ‘diverge’ means to branch out from a common point. Information from a single source is transmitted to several destinations and therefore, influence several neurons at the same time
Reverberating pathways involve neurones later in the pathway possess axon branches that form synapses with neurones earlier in the pathway and therefore send the impulse back through the circuit.
neurones later in the pathway synapse with earlier ones sending the impulse back through the circuit

5. Development of new neural pathways
Neurones and neural pathways are not fixed or ‘hard-wired’
They undergo change during a person’s lifetime
The ability of brain cells to become altered as a result of new environmental experiences is called plasticity.

6. Plasticity

7. Plasticity
Major:
Functions of areas of the brain that are irreparably damaged are taken over by other areas
Minor:
The cerebrum can consciously over rule / suppress stimuli from other areas of the brain e.g. blinking

8. Plasticity experiments
Air pipette / eye suppression (visual distraction)
See page 263
Number counting with distraction (auditory distraction)

9. Development of new neural pathways
Plasticity of response is created when new neural pathways are developed to:
create new responses,
bypass areas of brain damage,
to suppress reflexes or responses to sensory impulses.