Neurones, Nerve Fibres And Peripheral Nerves

Question 0

Recognise the difference between myelinated and non-myelinated nerve fibres and ascribe particular roles to each

Answer 0

Myelination - Schwann cell wraps in several concentric layers with gaps (nodes of randier) for faster conduction - produced by glial cells (oligodendrocytes in CNS)
Autonomic nervous system - myelinated and un-myelination
Somatic nervous system - only myelination (faster action potentials)

Question 1

Describe the structure of a peripheral nerve

Answer 1

Toward CNS - afferent/sensory, away from CNS - efferent/motor
Axon (endoneureum) –> nerve fascicle (perineureum) –> entire nerve (epineureum)
Multipolar - multiple dendrites (most neurones)
Bipolar - one dendrite, one axon (retina)
Unipolar/pseudo-unipolar - no dendrites, one axon (primary sensory neurones)

Question 2

Outline the great variety of synaptic connections in the nervous system

Answer 2

Excitatory neurones release glutamate/aspartate

Inhibitory neurones release glycine/GABA

Question 3

Relate demyelination to a slowing of conduction velocity within a nerve

Answer 3

Saltatory propagation inhibited –> impulse has further to travel –> slower response e.g. Multiple Sclerosis - myelin sheath destructively removed and replaced by scar tissue

Question 4

Explain the role of glial cells

Answer 4

1. Astrocytes - blood/brain barrier, assist in transfer of nutrients and waste - CNS
2. Oligodendrocytes - myelination (up to 250 axons/cells) - CNS
3. Microglia - immune and inflammatory functions - both
4. Schwann cell - myelination (1 axon/cells) - PNS
5. Satellite - physical support of peripheral neurones (afferent and efferent)