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 …..
Be able to identify the following structures in a diagram:
Dendrites
Cell body
Axons
Myelin sheath
State the function of the above structures
State what is what meant by myelination
State the difference in impulse conduction between 2 year olds and adolescents and adults
Describe the effects of destroyed myelin sheaths
State 4 functions of glial cells

3. Neurones The CNS is complex network of: Nerve cells called NEURONES
They receive and transmit electrical signals
Glial cells
Support and maintain the neurones

4. The human body contain billions of neurones, which must all be coordinated to provide the body with rapid means of communication and control.
There are 3 types of neurones which are structurally adapted to suit their function:
Sensory neurones
Inter neurones
Motor neurones
Neurones

5. Structure of a Neurone
Cell body
Axon
Direction of impulse
Dendrites
Myelin Sheath
Node (gap lacking myelin)
Axon – a single nerve fibre that carries impulse away from cell body to the next neurone (or in the case of motor neurone, to the muscle or gland)
Cell body – control centre of cell’s metabolism, contains a nucleus and clusters of ribosomes
Dendrites – (several) receive nerve impulses and pass them onto the cell body
Myelin Sheath - fatty material which surrounds the axon which:
Insulates the axon and
Increases speed of conduction from node to node

6. Remember the pathway!
DENDRITES
CELL BODY
AXON

7. Myelination
Myelination is the development of myelin around axon fibres
It is a long process – myelination is not complete at birth, so continues from birth to adolescence.
As a result, responses to stimuli in the first two years of life are not as rapid or coordinated as those of an older child or adult

8. Myelination

9. Destruction of myelin sheaths
In some diseases (such as polio, multiple sclerosis and Tay-Sachs disease) the myelin sheath around the axons becomes destroyed or damaged.
This can cause a loss in coordination and therefore affects physical movement

10. Polio Multiple Sclerosis Tay-Sachs disease Name of Disease Causes
Symptoms
Treatment
Polio
Multiple Sclerosis
Tay-Sachs disease

11. Polio
Caused by virus
Virus spreads along nerve pathways destroying motor neurones
Fever, neck and back muscle pain, asymmetrical weakness of certain muscles, paralysis of 1 or more limbs
No cure
Only pain treatment
Polio vaccine for prevention

12. Multiple Sclerosis Unknown cause
Some studies suggest autoimmune destruction of myelin sheaths
The demyelinated nerve fibres are unable to transmit nerve impulses efficiently
Numbness, walking difficulties, impaired vision, progressive loss of coordination, can be persistent or sudden attacks
No cure
Helping to regain functions after attacks
Other treatments to reduce attacks available, but they have adverse side effects

13. Tay-Sachs Disease
Caused by a genetic disorder where by the sufferer will inherit a defective recessive allele from both parents
Sufferer cannot make an enzyme which breaks down a fatty material, so this fatty substance builds up around the neurones – they become swollen (distended) and incapable of functioning
Region of retina shows up as a red spot
Infantile TSD = continuous deterioration of physical and mental abilities from 6 months, deaf, blind, paralysis, death at 4 years
No cure. Care can be given to ease symptoms

14. Glial Cells Several types of glial cells
Physically support neurons and produce the myelin sheath.
They also maintain a homeostatic environment around the neurones and remove debris by phagocytosis.

15. Task: use page 248 to label your diagram

16. Summary