1. The Nervous System and the Brain
Higher Human Biology
Subtopic 19
Nerve Cells and Neural Pathways

2. Learning Intentions To describe the structure and function of neurons
To explain the function of the myelin sheath
To state the function of glial cells

3. Neurones
Neurones provide the body with rapid communication and control
They conduct nerve impulses from on one part of the body to another

4. Types of Neurone SENSORY NEURONES MOTOR NEURONES
From sense organs to CNS
MOTOR NEURONES
From CNS to effectors
ASSOCIATION / RELAY / INTER NEURONES
From sensory neurones to motor neurones.
Are in CNS

5. SENSORY NEURONE
DIRECTION OF IMPULSE

6. MOTOR NEURONE
DIRECTION OF IMPULSE

7. ASSOCIATION NEURONE

8. Basic Neurone Structure
Each neuron consists of a :
Cell body
Axon
Dendrites (extensions of the cytoplasm)

9. Cell body contains cytoplasm and all major cell organelles
controls cell metabolism
has ribosome clusters for production of various proteins
association neurone cell bodies are in the CNS

10. Dendrites - nerve fibre extensions sensory dendrites - one long fibre
- transmit impulses from receptors to the cell body.
- association and motor dendrites
- many short fibres
- collect impulses from other neurones
- pass signal to the cell body

11. Basic neurone structure
Axon
single nerve fibre
carries impulses away from the cell body to the next neurone (if sensory/association)
carries impulse to effector (if motor)
ends with many branches to maximising contacts allowing successful transmission of an impulse

12. Basic neurone structure
Nerve impulses always travel in the following direction….
DENDRITES CELL BODY AXON

13. Neurones dendrites axon Cell body motor sensory relay
Dendrites are nerve fibres which receive nerve impulses and pass them towards a cell body
The cell body of a neurone contains the nucleus and most of the cytoplasm. It is the control centre of the cells metabolism and contains ribosomes which are needed for production of enzymes for the synthesis of neurotransmitters.
Axon a single fibre which carries nerve impulses away from the cell body.axon very long up to a metre.
Dendrites cell body axon
Cell body
sensory
relay

15. Myelin sheath sheath of fatty material that insulates an axon
contains small gaps called nodes
it increases the speed of transmission

16. Myelination……..
……….is the development of myelin around the axon fibres.
continues into adolescence
hypothalamus not fully myelinated until about 6 months – thermostat not fully operative
lower body spinal cord not fully myelinated until about 2 years - infant does not have full control over their lower body.

17. Diseases multiple sclerosis and poliomyelitis
myelin sheath is damaged or destroyed
results in loss of muscular coordination

18. They provide physical support to neurons but DON’T transmit impulses.
Glial Cells
They provide physical support to neurons but DON’T transmit impulses.

19. Functions of Glial Cells
form the myelin sheath around axons
provide nutrients to neurons, maintain their extracellular environment, and provide structural support
scavenge pathogens and dead cells by phagocytosis

20. Learning Intentions To describe the structure and function of neurons
To explain the function of the myelin sheath
To state the function of glial cells