Histology of the CNS

Question 1

How does a nerve signal travel through the nerve?

Answer 1

from dendrite –> cell body –> axon

Question 2

What are dendritic spines?

Answer 2

processes on dendrites increase surface area so it is more receptive to signals

Question 3

What is nissl substance?

Answer 3

large, basophilic masses of free polysomes and RER in cell bodies of neurons

Question 4

What is the terminal arborization?

Answer 4

distal end of the axon some have branching, collateral branches

Question 5

What are telodendria?

Answer 5

dilation of axon branch ends

contact postsynaptic cleft

Question 6

What is the most common type of neuron found throughout CNS? What does it look like?

Answer 6

multipolar

many dendrites, one long axon

Question 7

What does a unipolar neuron look like? Where is it found?

Answer 7

cell body w/ single short process w/ one main axon peripheral process to dendrites central process to end of axon sensory = dorsal root ganglia and cranial ganglia

Question 8

Where are bipolar neurons found and what do they look like?

Answer 8

one long dendrite w/ one long axon

sensory neurons of retina, olfactory mucosa, and inner ear

Question 9

What do anaxonic neurons look like and where are they found?

Answer 9

lack true axons and do not produce action potentials, but regulate local electrical changes of adjacent neurons

just a bunch of dendrites around cell body

Question 10

What type of neurons compromize 99% of all neurons in adults?

Answer 10

interneurons = btw other neurons

Question 11

What is contained in the presynaptic terminal bouton?

Answer 11

mitochondria

synaptic vesicles

Question 12

What is contained in the postsynaptic cell membrane?

Answer 12

receptors for the NT

ion channels to initiate a new impulse

Question 13

How does an electrical synapse work?

Answer 13

current flow occurs via gap junctions = link pre and postsynaptic membrnes

*gap jxns contain connexon proteins

Question 14

What do astrocytes do?

Answer 14

help form BBB

regulate interstitial fluid composition

structural support and organization to CNS

asst in neuron dev

replicate to occupy space of dying neurons

Question 15

What is neuropil?

Answer 15

fibrous intercellular network of cellular processes emerging from neurons and glial cells

Question 16

What do the perineural feet of astrocytes do?

Answer 16

clean debri

NT recycling

Question 17

What are glial fibrillary acid proteins?

Answer 17

reinforce intermediate filaments of proximal regions of astrocyte processes

Question 18

What are oligodendrocytes?

Answer 18

myelinate neuronal axons in cns

extend many processes that wrap around portion of a nearby axon

can wrap multiple neurons

*given axon covered by many oligodendrocytes

Question 19

When do oligodendrocytes work?

When do schwann cells work?

Answer 19

oligo: 6th months –> puberty
schwann: 4th month

Question 20

What cells myelinate axons in the PNS?

What are they derived from?

Answer 20

Schwann cells

NCC derived

myelinate motor roots before sensory

Question 21

What are ependymal cells?

Answer 21

columnar or cuboidal cells that line ventricles and central canal

apical end may have cilia and microvilli

facilitate mvt of CSF

joined by apical jxnal complexes

*no basal lamina

Question 22

Where is the choroid plexus found?

Answer 22

roofs of 3rd and 4th ventricles and parts of lateral ventrical walls

Question 23

What do microglia do?

Answer 23

phagocytic cells from monocytes

migrate to remove damaged/inactive synapses or other fibrous things

less numerous than oligodendrocytes or astrocytes

Question 24

What is grey and white in the spinal cord?

Answer 24

grey in center = ventral, dorsal, lateral horns

white mater in periphery: sensory and motor tracts

Question 25

Where is the central canal?

Answer 25

lies in central commissure of grey matter

lined by ependymal cells

Question 26

What are the 3 layers of the cerebellar cortex?

Answer 26

molecular layer = outer, light staining; mostly neuropil w/ scattered cell bodies

purkinje cells = at border btw molecular and granular layers

granular layer = dark, central, small, densely packed neurons

Question 27

What type of tissue makes up the cerebellar medulla?

Answer 27

white matter

Question 28

What is the substantia nigra?

Answer 28

large mass of grey matter extending throughout midbrain

divides cerebral peduncles into dorsal and ventral parts

neurons are multipolar

numerous neuromelanin granules

contain dopamine

Question 29

What are the 6 layers of the cerebral cortex?

Answer 29

1. Plexiform (neuroglia and horizontal cells of cajal)
2. Small pyramidal cell layer
3. layer of medium pyramidal cells
4. Granular layer
5. large pyramidal cell layer (motor)
6. polymorphic layer

Question 30

What is neocortex?

Answer 30

new layers of brain

archicortex = old

Question 31

What are the 3 layers of the hippocampus?

Answer 31

polymorphic layer: nerve fibers and small cell inerneurons

middle pyramidal cell layer

molecular layer: dendrites of pyramidal cells

Question 32

What are the 3 layers of the dentate gyrus?

Answer 32

polymorphic layer: nerve fibers and cell bodies of interneurons

middle granule cell layer: round, neuronal cell bodies of dentate granule cells

molecular layer containing dentrites of granule cells

Question 33

What is the hilus?

Answer 33

area where the head of the hippocampus abuts the dentate gyrus

multipolar neurons here = mossy cells

receive input from mossy fibers of granule cells of dentate gyrus –> relay signals back to other cells in dentate

Question 34

What occurs histologically in alzheimer’s?

Answer 34

striking thinning of gyri, esp frontal and temporal lobes

amyloid beta plaques in cortex

neurofibrillary tangles= accumulation of tau