Neuro Histology

Question 1

List five different types of glial cells

Answer 1

Astrocytes
Oligodendrocytes
Schwann cells
Ependymal cells
Satellite cells of ganglia

Question 2

What are microglia and where do they originate?

Answer 2

Immune cells of the CNS, originating from bone marrow

Question 3

How many layers of neurons are in the cortex?

Answer 3

6 layers differing in cell density and composition

Question 4

What is the role of the ventricular system?

Answer 4

Production and passage of CSF

Question 5

What is the choroid plexus and what is its role?

Answer 5

A vascular structure arising from the wall of each ventricle, which produces the CSF

Question 6

What are ependymal cells? What is their role?

Answer 6

Low columnar or cuboidal cells lining the ventricles within the brain and the central canal of the spinal cord; some have cilia to aid the flow of CSF

Question 7

How are ependymal cells different to normal epithelial cells?

Answer 7

They have a non-basal laminar (processes that extend deeply)

Question 8

What is the role of actin in neurons?

Answer 8

Dynamic assembly/disassembly of actin allows shape changes and movement or neurons (e.g. spines, growth cones)

Question 9

What is the role of intermediate filaments in neurons?

Answer 9

Intermediate filaments are found in all processes and are permanent

Question 10

What is the role of microtubules in neurons?

Answer 10

Microtubules are dynamic structures composed of tubulin which are responsible for axon transport of important proteins (e.g. neurotransmitters), vesicles and other molecules (e.g. lipids)

Question 11

What is the soma?

Answer 11

The metabolic centre of the neuron which gives rise to the dendrites and axon

Question 12

What is the role of dendrites?

Answer 12

To receive information from other neurons

Question 13

What is the role of the axon?

Answer 13

It acts as the main conducting unit for carrying signals to other neurons

Question 14

How is the volume of a neuron distributed and what does that mean in terms of pathology?

Answer 14

A high proportion of the total cell volume is in the axons and dendrites; for this reason, random damage often involves the axon, not the soma

Question 15

What cytological features reflect the neuron’s high level of protein production?

Answer 15

Large pale nucleus
Nissl bodies (composed of rough ER or free ribosomes)

Question 16

List five passive support functions of astrocytes

Answer 16

Neurotransmitter uptake and degradation
K+ homeostasis
Neuronal energy supply
Maintenance of the BBB
Injury response and recovery

Question 17

Name two active support functions of astrocytes

Answer 17

Modulation of neuronal function

Modulation of blood flow

Question 18

Why is K+ homeostasis important for maintaining normal neuronal function?

Answer 18

A high extracellular K+ concentration will cause neurons to continually depolarise; astrocytes “suck up” the excess to prevent this from occurring

Question 19

What is the result of inhibiting GABA and glutamate transporters on glial cells?

Answer 19

Greater magnitude and longer duration of depolarisation; this may lead to cell death

Question 20

List four factors which may initiate modulations in intracellular calcium inside glial cells

Answer 20

Neurotransmitters (e.g. ATP, glutamate)
Trauma
Inflammatory mediators
Spontaneous initiation

Question 21

How do glial cells communicate?

Answer 21

Via exocytosis of synaptic vesicles, similar to neurons

Question 22

How do glial cells modulate neuronal function?

Answer 22

ATP released from glia can produce inhibitory calcium waves in neurons

Question 23

How do glial cells modulate blood flow?

Answer 23

Calcium waves are initiated within an astrocyte and cause vasoconstriction or vasodilation

Question 24

What are oligodendrocytes and what is their role?

Answer 24

The predominant glial cell of white matter

Responsible for myelinating axons in the CNS

Question 25

What is the role of Schwann cells?

Answer 25

They are responsible for myelination of axons in the PNS

Question 26

What is the difference between the action of oligodendrocytes and Schwann cells?

Answer 26

Oligodendrocytes extend processes that wrap around parts of several axons, whilst Schwann cells wrap around only one axon

Question 27

Does the myelin sheath cover the entire axon?

Answer 27

No, there are small gaps called Nodes of Ranvier which increase speed of conduction

Question 28

What are the roles of microglia?

Answer 28

To rapidly respond to inflammation or injury by upregulating cytokines and growth factors
Contribute to development (normal function) and disease

Question 29

Describe the structure of a peripheral nerve

Answer 29

Individual nerve fibre and Schwann cell pairs are surrounded by loose vascular supporting tissue called endoneurium
Bundles of nerve fibres are called fascicles
Each fascicle is surrounded by collagenous tissue called perineurium
If there is more than one fascicle, these are separated by another layer of collagenous tissue called epineurium

Question 30

What is a ganglion and what does it contain?

Answer 30

An aggregation of neural cell bodies outside the CNS, also containing nerve fibres and satellite cells (support cells of the ganglia)

Question 31

What are the two types of ganglia and what is the role of each?

Answer 31

Sensory or dorsal root ganglia, which house the cell bodies of sensory neurons
Autonomic, which house the cell bodies of post-ganglionic neurons