The Nervous System

Question 1

Neuroglia and the CNS

Answer 1

Astrocytes
- major type in CNS (constitutes the brain blood barrier - BBB)
- assists in the transfer of nutrients and waste between blood and neurone
- phagocytic functions
- physical support for neurones
OLIGODENDROCYTES
- myelinated up to 250 different axons at a time
EPENDYMA
- line the ventricles and central canal of the spinal cord
MICROGLIA
- immune and inflammatory functions

Question 2

Neuroglia and the PNS

Answer 2

THE SCHWANN CELL 
- insulation of peripheral nerve axons - speeds up impulse conduction - 1 cell myelinates only 1 axon 
THE SATTELLITE CELLS 
- physical support for neurones 
MICROGLIA 
- immune and inflammatory functions

Question 3

The neurone (specialised functional unit of the nervous system) 
CELL BODY

Answer 3

Cell body
- 1 centrally placed nucleus
- 4-120uM diameter
- Nissl substance for protein synthesis
- Golgi apparatus for packaging of transmitters into vesicles
- some neurones have dendrites
Collections of cell bodies make up the Grey Matter
- Nerve nuclei - in CNS
- Collection of nerve cell bodies in PNS - called ganglia

Question 4

The neurone

THE AXON

Answer 4

Variable in thickness and in length

- thin (not myelinated) -

Question 5

Membranous envelopes of cranial and spinal nerves

out to in

Answer 5

Epineurium
- ensheaths the entire nerve
- interfascicular bands attach to adjacent nerve fascicle
Perineurium
- ensheaths a nerve fascicle (a collection of axons)
Endoneurium
- ensheaths a single cells axon

Question 6

Membranous envelopes of fibre tracts (CNS)

Answer 6

Are continuous with coverings of the brain and the spinal cord 
- are called meninges 
Out to in:
- dura mater 
- arachnoid mater 
- pKa mater

Question 7

Nerve injury

Answer 7

• seals up damage to prevent leakage of cell contents - nerve stump is formed
• distal segment is cut off from nutritional support of cell body
• distal segment of axon soon dies
• distal segment undergoes Wallerian degeneration
  NUCLEUS IS DISPLACED FROM CENTRE TO PERIPHERAL

Question 8

Neuroglia

Answer 8

• makes up 90% of the cells of the nervous system
  MICROGLIA
• from bone marrow
• the same subtype found throughout the body
  MACROGLIA
• from nervous tissue
• subtypes vary depending upon the division of the nervous system