LECTURE - The Central Nervous System

Question 1

cells of the CNS

Answer 1

• neurons
• glia
  > astrocytes
  > oligodendrocytes
  > ependyma
  > choroid plexus
  > microglia

Question 2

various morphologies of the neurons

Answer 2

• unipolar = sensory
• bipolar = olfactory
• multipolar (99%)

Question 3

NeuN IHC

Answer 3

labels neuronal cell bodies

Question 4

cresyl violet stain

Answer 4

• stains Nissl substance in neurons

- Nissl substance = rough ER, central to protein synthesis

Question 5

axons

Answer 5

• can be up to 1.5-2m long in a human (depending on height)

- contains neurotubules and neurofilaments

Question 6

where are neurotransmitters released?

Answer 6

at the synapse and they bind to receptors on dendrites

Question 7

synaptophysin

Answer 7

synaptic vesicle membrane protein

Question 8

dendrites

Answer 8

• conducts impulses to neuronal soma
• branch extensively near soma
• dendritic spines increase surface area for synaptic contact

Question 9

this silver stain is used to see dendrites

Answer 9

Golgi stain

Question 10

oligodendrocytes

Answer 10

• create myelin for dozens of different axons
• allows ‘saltatory’ conduction
  > to hop or leap
  > propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials
• myelin is an insulator!

Question 11

luxol fast blue

Answer 11

• a copper-phthalocyanine dye that is soluble in alcohol and is attracted to bases found in the lipoproteins of the myelin sheath
• myelin is blue, neuropil is pink, and neurons are purple

Question 12

multiple sclerosis (MS)

Answer 12

• characterized by plaques of myelin loss in the CNS

- LFB stain highlights myelin loss

Question 13

astrocytes

Answer 13

• highly branched
• intermediate filaments = glial fibrillary acidic protein
• processes contact:
  > dendrites, neuronal soma, some axonal surfaces and synapses
  > end feet coat blood vessels
  > joined end feet at surface if brain and spinal cord = glia limitans

Question 14

functions of astrocytes

Answer 14

• physical support
• guide neuronal migration
• metabolic support

Question 15

these stains astrocytes well

Answer 15

• LFB

- GFAP (glial fibrillary acidic protein)

Question 16

ependyma functions

Answer 16

- fluid homeostasis between brain parenchyma and CSF
 > secretion, absorption
 > brain CSF barrier 
- line ventricles
- have cilia, microvilli
- GFAP +

Question 17

choroid plexus

Answer 17

• secretes CSF (up to 500 mL/day); found in ventricles
• adapted from ependymal cells (specialized ependymal cells; ‘delicate knot’
• removes catabolites, foreign materials, and neurotransmitters from CSF

Question 18

microglia

Answer 18

• big and branchy if activated
• small, dark nucleus, often a bit elongated
• no cytoplasm on H&E
• CD68 IHC (macrophages of the brain)
• two or three processes emanate from each pole