Histology of the CNS Flashcards Preview

[OS 202] Lecture Exam A > Histology of the CNS > Flashcards

Flashcards in Histology of the CNS Deck (50):
1

What do you call the small expansions at the end of an axon?

Terminal Bouton

2

Where the soma extends into the axon?

Axon Hillock

3

Central region of cytoplasm around the nucleus crowded with organelles

Perikaryon

4

Cytoplasm of neurons contain granules callde?

Nissl Bodies

5

Smallest Filaments in the Cytoskeleton of Neurons

Actin Filaments (3-4 Nanometers)

6

Most prominent filaments of Neurons

Microtubules (24-28 Nanometers)

7

What are the most important of the filaments?

Why?

The microtubules

They are the pathways of neurotransmitters from cell to cell

8

Terminal Portion of an Axon

Motor End-Plate

9

What is Myelin called outside the CNS?
Inside the CNS?

Inside: Oligodendroglia
Outside: Schwann Cells

10

Types of Neurons According to Polarity (4)

1. Unipolar
2. Pseudo-Unipolar
3. Bipolar
4. Multipolar

11

Where are Unipolar Neurons found?

Describe features (Soma, Axon, Dendrites)

Only embryos, not in adults

Soma and axon only, no dendrites

12

Describe a Pseudo-unipolar Neuron (Axon, Dendrites, Sensory/Motor)

Very long axon and dendrites
Mostly sensory neurons

13

Bipolar Neuron Features (Axon, Dendrite)

Axon on one side, dendrites on the other

Two processes at opposite ends of soma

14

Where are Bipolar Neurons found?

Retinal Cells and Olfactory Epithelium

15

Describe Multipolar Neurons

Most common neurons

Many cytoplasmic processes but only one axon per cell

16

Examples of Multipolar Neurons

Pyramidal Cells
Purkinje Cells

17

Subtypes of Multipolar Neurons

Golgi Type 1: Long projecting axons
Golgi Type 2: Axons project locally (Do not leave the grey matter of the cerebral hemisphere)

18

3 Types of Neurons According to Function

1. Afferent Neurons
2. Efferent Neurons
3. Interneurons

19

[Afferent Neurons]

1. Sensory or Motor?
2. Where does it carry impulses from and where does it go?
3. What type of neurons are they?

Sensory/Receptor Neurons
Carry impulses from sensory towards CNS
Pseudounpilar type of neuron

20

[Efferent Neurons]

Where does it carry information from and to where?

From CNS -> Muscles/Glands

21

[Interneurons]

Function

Relay information between sensory and motor neurons

22

What are the most abundant type of neurons in the CNS?

Interneurons

23

[External Granular Layer]

Contains what kind of neurons?

Stellate Neurons

24

[External Pyramidal Layer]

Contains what kind of neurons?

Main source of?

Small pyramidal neurons

Cortical-Cortical Efferent Fibers

25

[Multiform Layer]

Characteristics

• Few large pyramidal neurons
• Many spindle-like neurons and multiform neurons • Difficult to distinguish under a light microscope
• Reciprocal connection to and from the thalamus

26

Layers of the Cerebral Cortex

1. Molecular
2. External Granular
3. External Pyramidal
4. Internal Granular
5. Internal Pyramidal
6. Multiform

27

How are Astrocytes stained?

Glial Fibrillary Acidic Protein

28

What do Astrocytes envelope?

Synapses

29

2 Kinds of Astrocytes

1. Fibrous
2. Protoplasmic

30

Where are Fibrous astrocytes found?
End feet attached to what?

Found in the white matter
Attached to capillary walls

31

Where are Protoplasmic astrocytes found?
End feet attached to what?

Found in gray matter
End feet envelope synapses

32

Functions: Astrocytes (9)

• Structural support
• Metabolic support (provide glucose to neurons)
• Regulate extracellular K+ concentration
• Regulate oligodendroctye myelinating activity
• Minimal role in maintaining BBB
• Reuptake and release of neurotransmitters
• Help regulate blood flow
• Nervous system repair (glial cell formation or gliosis)
• Fillers after injury to brain

33

Tumors that arise from Astrocytes

Astrocytomas

34

Differentiate a normal neuron from an astrocytoma

Normal: Pale staining nuclei
Astrocytoma: Dark nuclei

35

Function: Oligodendrocytes

Responsible for myelination of nerve fibers within the CNS

36

Ratio of Oligodendrocyte :: Myelinated Axons

1 : 50

37

Myelination starts at what age?

6-9 Years Old

38

Define: Nodes of Ranvier

Gaps between myelin sheaths which propagate electrical impulses faster (Saltatory Conduction: Node->Node)

39

Trivia: How big is the node of Ranvier

1mm

40

Cause: Cerebral Palsy (Periventricular Leukomalacia)

Damage to developing oligodendrocytes
Damaged by excessive release of glutamate

41

Cause: Oligodendroglioma

Tumors affecting glial cells

42

Effect: JC Virus

Can affect oligodendrocytes causing progressive multifocal leukoencephalopathy (PML)

43

Microglia cells are similar to what leukocytes?

Macrophages

44

Microglia originate from?

Myeloid Progenitor Cells

45

First line of defense against infection within the BBB?

Microglia

46

Functions: Microglia (10)

• First line of infection in blood brain barrier
• ‘Janitors’ for dead neurons
o Constantly moving, clearing dead neurons and debris
• ‘Alarm’
o Sensitive to slightest form of inflammation or infection
• Have unique K+ channels in their membrane which makes them
sensitive to smallest changes in potassium ion concentration
• Phagocytosis of foreign bodies/invaders
o Significant in patients with TB: bacteria could be swallowed but cannot be broken down so it persists in the brain and could cause TB meningitis
• Cytotoxicity: hydrogen peroxide, nitrous oxide, proteases, glutamate, aspartate (chemical warfare with collateral damage)
• Part of antigen presentation
• Pruning of synapses (removing of bad immature behaviours or
childishness)
• Promotion of repair
• Extracellular signalling (cytokines)

47

Function: Ependymal Cells

Involved in CSF Production
Absorb and recycle neurotransmitters

48

What kind of cells make up Ependymal Cells?

Columnar and Cuboidal with Cilia

49

Modified Ependymal Cells + Capillaries =?

Choroid Plexuses

50

Schwann Cells are like?

Oligodendrocytes in the PNS but only 1:1 ratio
This is important in regeneration of damaged axons