Histology of the Nervous System

Question 1

What is the key cell of the nervous system?

Answer 1

Neuron

Question 2

What are the types of glial cells?

Answer 2

Astrocytes
Oligodendrocytes
Schwann cells
Ependymal cells
Satellite cells of ganglia

Question 3

What are the immune cells of the CNS?

Answer 3

Microglia

Question 4

How many glial cells are there?

Answer 4

Almost as many as neurons

Question 5

How many layers of neurons are there in grey matter?

Answer 5

6

Question 6

What colour does the cell body stain with H&E?

Answer 6

Pink

Question 7

What colour do the processes stain with H&E?

Answer 7

Pink

Question 8

What is highlighted with a silver stain?

Answer 8

Processes

Question 9

What does the ventricular system do?

Answer 9

Form and provide passage for CSF

Question 10

What is the choroid plexus?

Answer 10

Vascular structure arising from ventricles

Question 11

What does the choroid plexus do?

Answer 11

Form CSF

Question 12

What cell type are ependymal cells?

Answer 12

Low columnar or cuboidal

Question 13

Where are ependymal cells found?

Answer 13

Line central canal of spinal cord and ventricles in brain

Question 14

T/F: Ependymal cells in some areas have cilia. If true, why?

Answer 14

True, to help CSF flow

Question 15

Are ependymal cells epithelial or glial?

Answer 15

Neither, but they’re more glial than epithelial

Question 16

How are ependymal cells attached to underlying tissue?

Answer 16

Via long processes anchoring cell in tissue

Question 17

What are some characteristics of neurons?

Answer 17

Morphologically distinct
Electrically active
Rapid communication
Long distance
Specialised; eg:
- Retina
- Cochlea
High level of protein synthesis
Metabolically limited
Terminally differentiated

Question 18

Where are Purkinje cells found?

Answer 18

Cerebellar cortex

Question 19

Where are pyramidal cells found?

Answer 19

Cerebral cortex

Question 20

What are the three components of a neuron’s cytoskeleton?

Answer 20

Actin
Intermediate filaments
Microtubules

Question 21

What is the role of actin in a neuron’s cytoskeleton?

Answer 21

Dynamic assembly/disassembly
Allows shape changes and movement; eg:
- Spines grow during learning
- Growth cones

Question 22

What is the role of intermediate filaments in a neuron’s cytoskeleton?

Answer 22

In all processes

Permanent

Question 23

What is the role of microtubules in a neuron’s cytoskeleton?

Answer 23

Dynamic
Made of tubulin
Axon transport

Question 24

What does the soma do?

Answer 24

Metabolic centre of cell

Question 25

What are the two types of neuronal processes?

Answer 25

Dendrite | Axon

Question 26

What does a dendrite do?

Answer 26

Receive information from other neurons | = Input

Question 27

What does an axon do?

Answer 27

Main conducting unit for carrying signals to other neurons | = Output

Question 28

Where is a high proportion of total cell volume?

Answer 28

Axons (and dendrites)

Question 29

Why is axonal transport critical?

Answer 29

To supply cell-body derived elements to long axon

Question 30

Which part of the neuron does random damage often involve?

Answer 30

Axon, not cell body

Question 31

Describe graded membrane potentials

Answer 31

Unequal distribution of positively charged ions on either side of membrane Membrane has Na-K-ATPase pumps and ion channels - sets up charge distribution across membrane

Question 32

What type of signal is sent via dendrites?

Answer 32

Passive spread of current - local signal

Question 33

What type of signal is sent via axons?

Answer 33

Action potential - travels long distances

Question 34

Describe the synapse

Answer 34

Pre-synaptic cell talks to something - Synaptic vessels contain neurotransmitters Synaptic cleft = space between communicating processes Post-synaptic cell receives information > change in membrane potential > responds to information

Question 35

What is the high level of protein production in neurons needed for?

Answer 35

Ion channels Receptors Cytoskeleton

Question 36

How do you identify a highly synthetic cell in cytology?

Answer 36

Large pale nucleus | Nissl bodies

Question 37

What are Nissl bodies?

Answer 37

Organelles that make proteins - Rough ER - Free ribosomes

Question 38

Where is protein made in a neuron?

Answer 38

Cell body only

Question 39

What is another name for glia?

Answer 39

Macroglia

Question 40

Where are glia derived from?

Answer 40

Neuroectoderm, like neurons

Question 41

Where are microglia derived from?

Answer 41

Bone marrow, like other immune cells

Question 42

What are the passive support functions of astrocytes?

Answer 42

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

Question 43

Why is neurotransmitter uptake and degradation important?

Answer 43

Otherwise signal continuous

Question 44

What does too much K in the ECF mean for the neuron?

Answer 44

Overstimulation

Question 45

How is glucose transported across the BBB?

Answer 45

Blood > astrocytes > neurons

Question 46

How do astrocytes contribute to the BBB?

Answer 46

Wrap around blood vessels

Question 47

What are the active functions of astrocytes?

Answer 47

Modulation of neuronal function | Modulation of blood flow

Question 48

Why can astrocytes carry out their active functions?

Answer 48

Electrically coupled | Send signals

Question 49

What type of neurotransmitter is glutamate?

Answer 49

Excitatory

Question 50

What type of neurotransmitter is GABA?

Answer 50

Inhibitory

Question 51

Describe the cycling of glutamate across the synapse

Answer 51

1. Glutamate released into synapse 2. Glutamate detected by glutamate receptor on glial cell 3. Glutamate enters glial cell 4. Converted to glutamine - toxic otherwise 5. Glutamine shunted back to neuron

Question 52

Describe the cycling of GABA across the synapse

Answer 52

1. GABA released into synapse 2. GABA detected by GABA receptors on glial cell 3. GABA enters cell 4. GABA shunted into Krebs cycle 5. Glutamine also shunted to neuron for GABA synthesis

Question 53

What happens when glutamate transporters on glial cells are inhibited?

Answer 53

Neurons depolarise more | Increase in signal strength and duration > too metabolically active > neuronal death

Question 54

What is the intracellular ion that changes in concentration in astrocytes?

Answer 54

Ca

Question 55

What does modulation in IC Ca allow a glial cell to do?

Answer 55

Release of neuronal modulatory substances

Question 56

What initiates Ca modulation in astrocytes?

Answer 56

``` Neurotransmitters like: - ATP - Glutamate Trauma Spontaneous Inflammatory mediators ```

Question 57

T/F: Glial cells have synaptic vesicles and show exocytosis

Answer 57

True

Question 58

How does an increase in IC Ca in glial cells affect neurons?

Answer 58

Inhibited by Ca wave | Mechanism involves release of ATP from glia

Question 59

How do astrocytes regulate vascular tone?

Answer 59

Ca wave in astrocyte causes vasoconstriction/vasodilation

Question 60

What is the predominant glial cell of white matter?

Answer 60

Oligodendrocyte

Question 61

What do oligodendrocytes do?

Answer 61

Myelinate axons in CNS

Question 62

What do Schwann cells do?

Answer 62

Myelinate axons in PNS

Question 63

Why is myelination important?

Answer 63

Provide electrical insulation | Speeds up conduction

Question 64

What else other than myelination speeds up conduction?

Answer 64

Increased axon diameter

Question 65

How many axons do oligodendrocytes myelinate?

Answer 65

Several

Question 66

How many axons do Schwann cells myelinate?

Answer 66

One

Question 67

What breaks up the myelin sheath?

Answer 67

Nodes of Ranvier

Question 68

What is the role of the nodes of Ranvier in signal transduction?

Answer 68

Signal jumps from node to node | Rapid propagation of signal

Question 69

T/F: CNS is immune priveleged

Answer 69

True

Question 70

What is the role of microglia

Answer 70

Surveillance Local defence Brain development Disease

Question 71

What happens to microglia during inflammation or injury?

Answer 71

Change rapidly | Resemble macrophages

Question 72

Describe the histological structure of a peripheral nerve

Answer 72

Made up of nerve fibres Each nerve fibre and Schwann cell surrounded by loose vascular supporting tissue = endoneurium Fascicles = one or more bundles of nerve fibres Each fascicle surrounded by collagenous tissue = perineurium Bundles of fascicles wrapped in epineurium

Question 73

What are ganglia?

Answer 73

Aggregations of cell bodies outside of CNS

Question 74

What are the types of ganglia?

Answer 74

Sensory | Autonomic

Question 75

What are sensory ganglia?

Answer 75

House cell bodies of sensory neurons | Eg: dorsal root ganglia

Question 76

What are autonomic ganglia?

Answer 76

House cell bodies of post-ganglionic neurons

Question 77

What makes up ganglia?

Answer 77

Cell bodies Nerve fibres Satellite cells

Question 78

What are satellite cells?

Answer 78

Supporting cells in ganglia