Lecture 4: Histology of CNS

Question 1

What substance causes neurons to appear opaque in a histological staining?

What does it represent?

Answer 1

Nissl substance/bodies

Represents large, basophilic masses of free polysomes and Rough ER due to neurons being highly metabolic

Question 2

What is the role of dendritic spines?

Answer 2

Known for their plasticity and ability to increase receptive area of the neurons

Increase in Surface Area

Question 3

What are telodendria?

Answer 3

Dilation of branch ends of axons that contact postsynaptic cells

Question 4

What is a neuropil?

Answer 4

The surrounding meshwork and structure that support the neuronal cell bodies

• Works with glial cells*
• Not part of cell body!*

Question 5

What type of neuron is most common throughout the CNS?

What do they function as?

Answer 5

Multipolar

Motor neurons, CNS interneurons

Question 6

What is the most common function of bipolar neurons?

Answer 6

Sensory neurons of retina, olfactory mucosa, and inner ear

Question 7

What type of neuron is found in dorsal root and cranial ganglia?

Answer 7

Unipolar/Pseudounipolar

Question 8

What motor protein is utilized in anterograde transport?

Answer 8

Kinesin (uses ATP)

Cell body –> axon

Question 9

What motor protein is utilized by retrograde transport?

Answer 9

Dynein

Axon –> Cell Body

Question 10

What is the speed of slow transport?

What type of transport is this utilized by?

Answer 10

0.2-4 mm/day

Anterograde

Examples: Cytoskeletal Elements

Question 11

What is the speed of fast transport?

What is conveyed in either direction?

Answer 11

20-400 mm/day

Anterograde: Membrane-limited organelles, sER components, synaptic vesicles, mitos

Retrograde: membrane-limited organelles, molecules endocytosed at axon terminal (toxins and viruses)

Question 12

Most synapses in the body are ___ synapses.

Answer 12

Chemical

Utilizing NT

Question 13

How does electrical current pass through neurons?

Answer 13

Gap junctions

Connexon proteins connect pre and post synaptic membranes

Question 14

On a histological image, what would differentiate between a chemical and electrical synapse?

Answer 14

Chemical synapse has a vesicular presynaptic cell

Electrical synapse has visible connexon protiens

Question 15

What is the function of glial cells?

Answer 15

Support cells involved in conduction speed, repair, neurotransmitter maintenance

Question 16

What are types of glial cells found in the CNS?

Answer 16

• Astrocytes
• Oligodendrocytes
• Ependymal cells
• Microglia

Question 17

What is the function of astrocytes?

Answer 17

• Prevent leakage into Blood Brain Barrier
• Moderate NT Intake
• Clear Debris

Question 18

Astrocytes produce perivascular feet that perform what function?

Answer 18

Modulate blood flow and move nutrients and metabolites between neurons and capillaries

Question 19

What protein reinforces the proximal regions of astrocytes?

Answer 19

Glial Fibrillary Acid Protein (GFAP)

Stains Green

Question 20

What is the role of oligodendrocytes?

Answer 20

Myelinate axons from multiple neurons

Similar to Schwann Cells in PNS

Question 21

What type of epithelium are ependymal cells?

Where are they found?

Answer 21

Columnar or cuboidal cells lining ventricles of the brain and central canal of spinal cord

Question 22

What is the role of ependymal cells?

Answer 22

Facilitale CSF movement

Question 23

What is the choroid plexus composed of?

Answer 23

Thin layer of well-vascularized pia mater covered by cuboidal ependymal cells

Question 24

Where is choroid plexus found?

Answer 24

Roofs of 3rd and 4th ventricles

Parts of lateral ventricular walls

Question 25

What does the choroid plexus do?

Answer 25

• Removes water from blood and releases it as CSF
• Has tight junctions to prevent leakge of Blood-CSF barrier

Question 26

What are fronds?

Answer 26

Branches of choroid plexus that forms a villous structure

Question 27

What neural cells act similar to phagocytes and are the major mechanism of immune defense in the CNS?

Answer 27

Microglia

Question 28

In the spinal cord, where is gray and white matter located?

Answer 28

Gray Matter: Internal

White Matter: External

Sacral region has more gray matter than cervical

Question 29

How can you tell the difference between anterior and posterior horn?

Answer 29

• Can look for motor cell bodies in anterior horn
• Most of the time, anterior horn is bigger

Question 30

Where is the central canal located?

What is its significance?

Answer 30

• Central commissure of grey matter
• Lined by ependymal cells and has CSF

Question 31

What are the three layers of cerebellar cortex?

Answer 31

• Molecular Layer: ​Lot of neuropil
• Purkinje Cells: ​Thin layer with dendrites that extend through the moleculer layer
• Granular Layer: ​Densly packed neurons

Question 32

What are the cerebral cortical layers?

Answer 32

• Molecular Layer: ​Mostly neuroglial cells and horizontal cells of Cajal
• External Granular Layer: Small pyramidal cells and granule cells
• External Pyramidal Layer: Medium pyramidal cells
• Inner Granular Layer: Small granule cells
• Ganglionic Layer: Huge pyramidal cells (Betz)
• Multiform Layer: Fusiform Cells

Question 33

What cortical layers contain the pyramidal cells?

Answer 33

Layer 2: Small pyramidal cells

Layer 3: Medium pyramidal cells

Layer 5: Large pyramidal cell layer - Betz Cells

Question 34

What tissue is this?

What is the outer layer? What is the deep layer?

Answer 34

Cerebral Cortex

• Outer Layer: Molecular Layer
• Deep Layer: Multiform Layer

Question 35

A patient’s MRI shows thinning of cerebral gyri in the frontal and temporal lobes. What disease process is associated with this finding?

Answer 35

Alzheimer’s disease

Question 36

What structures are found in a histological slide for a patient with this disease?

Answer 36

Amyloid B plaques

Neurofibrillary tangles: abnormal accumulation of tau

Question 37

Where is dopamine found?

Answer 37

Neuromelanin pigments in substantia nigra

Question 38

What are some features of Parkinson’s Disease on a histological slide?

Answer 38

• Lewy Bodies
• Pale halo
• Aggregates of α-synuclein