04. Neurohistology (Dennis)

Question 1

What defines an ependymal cell as a choroid plexus cell histologically?

Answer 1

Association with pia mater and associated vasculature.

Question 2

Do ependymal cells have a basal lamina?

Answer 2

Nope.

Question 3

What are the functions of ependymal cells?

Answer 3

production of CSF

arachnoid villi reabsorb

Question 4

What are the functions of astrocytes?

Answer 4

• BBB
• Reuptake NTMs
• Regulate Ion Concentration

Question 5

The proximal regions of astrocytes are reinforced by what protein?

Why do we care?

Answer 5

GFAP: Glial Fibrillary Acid Protein

GFAP can be preferentially stained to highlight astrocytes.

Question 6

What are the six layers of the neocortex?

Answer 6

1. Plexiform Layer (molecular layer)
2. Small pyramidal cell layer (external granular layer)
3. Layer of medium pyramidal cells (external pyramidal cell layer)
4. Granular layer (internal granular layer)
5. Large pyramidal cell layer (ganglionic layer)
6. Polymorphic layer (multiform / polymorphic cell layer)

Question 7

What are the three layers of the hippocampus?

What are the three layers of the dentate gyrus?

What is contained within each of these layers?

Answer 7

Hippocampus

1. Polymorphic layer
   
   1. Nerve fibers and small cell bodies of interneurons
2. Middle pyramidal layer
   
   1. Hippocampal pyramidal cells
3. Molecular layer
   
   1. Dendrites of the pyramidal cells

Dentate Gyrus

1. Polymorphic layer
   
   1. Nerve fibers and cell bodies of interneurons
2. Middle granular layer
   
   1. Round neuronal cell bodies of dentate granule cells
3. Molecular layer
   
   1. Dendrites of granule cells

Question 8

Where do we find the choroid plexus?

Answer 8

In the roof of the 3rd and 4th ventricles, and in parts of the lateral ventricular walls.

Question 9

Describe the histological changes associated with Alzheimer’s disease.

Answer 9

The gyri of the cortex thin, and the brain becomes smoother.

β-amyloid plaques and tau (τ) neurofibrillary tangles are identified on sections, as well as neuronal loss.

These plaques interrupt communication between neurons.

Tau proteins form “skeins.”

Question 10

What cells are responsible for myelination of the CNS?

What embryological layer are these cells derived from?

Answer 10

Oligodendrocytes

• promiscuous-like to touch many axons, single axon wrapped by many oligo.
• appear as small cells, rounded, condensed, unstained cytoplasm

Neuroepithelium

Question 11

What cells are responsible for myelination of the PNS?

What embryological layer do these come from?

Answer 11

Schwann cells

Neural crest cells

Question 12

What motor proteins are used in anterograde and retrograde transport, respectively?

Answer 12

Anterograde = kinesin.

Retrograde = dynein.

Question 13

What is the function of microglia in the CNS?

Answer 13

They are the primary defense from microbial invaders.

Originate from monocytes.

Question 15

What is “neuropil?”

Answer 15

Neuropil: dense network of interwoven nerve fibers &
their branches and synapses, together with glial filaments

Question 16

What molecules utilize slow transport, and which direction are they headed?

Answer 16

Anterograde only

Tubulin molecules, actin molecules, & neurofilament proteins

Question 17

What is the function of the choroid plexus?

Answer 17

Modified ependymal cells release CSF.

Question 18

What is this tissue?

Answer 18

molecular layer-neuropil and neuronal cell bodies

purkinje cells-extend dendrites throughout the molecular layer as branching nerve fibers

granular layer-contians various small neurons (granules) and little neuropil

organized into folia with the cerebellar medulla located deep

Question 19

Where do we find bipolar neurons?

Answer 19

Sensory neurons of the retina, olfactory mucosa,
and inner ear

Question 20

Where do we find unipolar / pseudounipolar neurons?

Answer 20

“Other” sensory neurons, including
the dorsal root ganglia & cranial ganglia

Question 21

What do we call the grainy substance found in a neuron?

Answer 21

Nissl substance / bodies.

Question 22

Slow Transport

Vs.

Fast Transport

Answer 22

anterograde-cytoskeletal elements

bidirectional-retrograde movement of toxins/viruses (shingles)

Question 23

Axonal synapses

Answer 23

Not always axon to dendrite

can be axon to soma or axon to axon

allows modulation of signals

Question 24

Electrical Synapse

Answer 24

Uses gap junctions

links pre- and post-synaptic membranes

contains connexon proteins

found in retina, olfactory, and inf. olivary nucleus

Question 25

Cortical Layers

Answer 25

I. Molecular layer-gibers, travel parallel to surface

II. External granular layer-small pyramidal cells and granule cells

III. External pyramidal layer-pyramidal cells are larger and posses pyramid shape

IV. Inner granular layer-small granules

V. Ganglionic Layer-pyramidal cells are large in motor areas

VI. Multiform layer-cells with diverse shapes, fusiform cells

Question 26

Alzheimer’s Disease

Answer 26

Amyloid-B plaques-amorphous, pink masses in the cortex

Neurofibrillary tangles-flame shaped skeins formed by abnormal accumulation of tau

Question 27

Parkinson’s and Substantia Nigra

Answer 27

Neuromelanin pigment makes up the substantia nigra

contains dopamine–>inhibitory effects in brain areas dedicated to movement

in Parkinson’s, there is degeneration of the neurons in the substantia nigra–>loss of dopamine, Lewy bodies, alpha-synuclein seen on slides

Question 28

Cerebral Cortex

Answer 28

• Old part-archicortex
• Neocortex is most of it and is six layers

1. pyramidal cells
2. granule cells
3. cells of martinotti
4. fusiform cells
5. horizontal cells of cajal