Cells of the Nervous System

Question 1

What are the protrusions coming out of dendrites called?

Answer 1

Dendritic spines

Question 2

Describe the arrangement of primary, secondary and tertiary dendritic spines.

Answer 2

Primary dendritic spines come off the vertices of the pyramid
Secondary dendritic spines come off the primary
Tertiary dendritic spines come off the secondary

Question 3

Where do axons originate?

Answer 3

Axon hillock

Question 4

How does the diameter of the axon change as it moves further from the cell body?

Answer 4

It doesn’t - the axon diameter stays the same the whole distance and so the conduction velocity remains the same the whole way

Question 5

Describe the cytoskeleton of axons.

Answer 5

They have abundant intermediate filaments and microtubules

Question 6

What are the three domains of an axon? Describe them.

Answer 6

Paranode - next to the node - where there are tight junctions between the ends of the myelin sheath and the axon
Juxtaparanode - next to the paranode, underneath the myelin sheath - potassium and calcium channels are found here

Question 7

What are the two forms of axon terminal?

Answer 7

Butons and Varicosities

Question 8

Where are varicosities found?

Answer 8

Along smooth muscle where one axon will stimulate the contraction of several smooth muscle cells

Question 9

What are the three arrangements of axons?

Answer 9

Axo-axonic
Axo-somatic
Axo-dendritic

Question 10

Describe fast axonal transport. What is a key feature of axonal transport?

Answer 10

Vesicles of neurotransmitter are carried along microtubules
These microtubules are unidirectional because the microtubules are polarised. There is retrograde transport but that occurs along other unidirectional microtubules.

Question 11

What happens when the axon is damaged during multiple sclerosis?

Answer 11

If there is a restriction in the axon then you begin to see swellings caused by the accumulation of neurotransmitter.

Question 12

What is the difference between Golgi Type I cells and Golgi Type II cells?

Answer 12

Type 1 has long axons whereas Type II have short axons

Question 13

What is the most abundant cell type in the CNS and what roles do these cells have?

Answer 13

Astrocytes - they are the support cells of the central nervous system
They are facultative macrophages, they are part of the blood brain barrier, they are involved in homeostasis - soaking up neurotransmitter, scaffold of neuronal migration and axon growth

Question 14

What are the two types of oligodendrocyte?

Answer 14

Interfascicular and Perineuronal

Question 15

Give two myelin disease states.

Answer 15

Adrenoleukodystrophy

Multiple Sclerosis

Question 16

What is the role of microglia?

Answer 16

They are the immune cells of the CNS

Question 17

State some structural features of the cell body, dendrites and axons.

Answer 17

Cell body - large nucleus with prominent nucleolus, abundant rough ER, well developed Golgi, large number of mitochondria
Dendrites - spread from cell body and branch frequently, dendritic spines receive majority of synapses
Axon - emerges at axon hillock, one axon per cell but they branch extensively, microtubules and neurofilaments are prominent

Question 18

Where are Golgi Type I and Golgi Type II cells found?

Answer 18

Golgi Type I - pyramidal cells of the cerebral cortex, purkinje cells of the cerebellum, anterior horn cells of the spinal cord, long axons
Golgi Type II - short axons, stellate cells of the cerebral cortex and cerebellum

Question 19

What is the normal morphology of sensory neurones?

Answer 19

Pseudounipolar - two branches, one running to the CNS and another to the sensory receptor

Question 20

State some differences between the axo-dendritic, axo-somatic and axo-axonic synapses.

Answer 20

Dendritic - excitatory
Somatic - inhibitory
Axonic - modulatory

Question 21

What are the differences between Gray’s type I and Gray’s type II synapses?

Answer 21

Grays Type I = vesicles are clear and rounded - EXCITATORY

Grays Type II = vesicles are oval or flattened - INHIBITORY

Question 22

What are the subtypes of astroglia?

Answer 22

Fibrous astrocytes
Protoplasmic astrocytes
Radial glia

Question 23

State some functions of astroglia, oligodendroglia, microglia and ependymal cells.

Answer 23

Astroglia
Formation of blood-brain barrier
Transporting substances between circulation and neurons
Removal and degradation of neurotransmitters
Release of neurotrophic factors
Response to injury - glial scar formation
Oligodendroglia
Myelin forming cells of the CNS
Elaboration and maintenance of myelin sheath
Axonal regeneration
Microglia
Resident macrophages of the CNS
Antigen presentation
Role in tissue remodelling
Synapse stripping
Ependymal Cells
Line the ventricles and central canal
Choroid plexus produces cerebrospinal fluid