Neuro 1 - Cells of the nervous system

Question 1

Define neuron

Answer 1

A neurone is an electrically excitable cell that receives, processes, and transmits information through electrical and chemical signals. It is the basic structural and functional unit of the nervous system.

Question 2

List features of neurons

Answer 2

Large nucleus
Prominent nucleolus
Abundant rER
Well developed Golgi (because of need to transport proteins over long distances)
Abundant mitochondria
Highly organised cytoskeleton
HIGHLY ORGANISED METABOLICALLY ACTIVE CEL

Question 3

What are the protrusions coming out of dendrites called?

Answer 3

Dendritic spines

–> one of the most plastic elements of the nervous system

Question 4

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

Answer 4

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 5

Where do axons originate?

Answer 5

Axon hillock

Question 6

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

Answer 6

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

Question 7

Which cell is known to have an enormous number of spines?

Answer 7

Purkinje neurons of the cerebellum

Question 8

Describe the cytoskeleton of axons.

Answer 8

They have abundant intermediate filaments (neurofilaments) and microtubules

Question 9

Where are Na+ and K+ channels located on a myelinated fiber?

Answer 9

Na+ are located at the node of Ranvier to amplify signal, K+ are located at the juxtaparanode to repolarise
(juxtaparanode-paranode(where myelin attaches to axon)-node)

Question 10

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

Answer 10

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 11

What are the two forms of axon terminal?

Answer 11

Boutons and Varicosities

Question 12

Where are varicosities found?

Answer 12

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

Question 13

What are the three arrangements of axons/synapse?

Answer 13

Axo-dendritic - often escitatory
Axo-somatic - often inhibitory
Axo-axonic - often modulatory

Question 14

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

Answer 14

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, these are different organelles from the anterograde
They use different microtubules - have diffrent +/- ends
Highly organised cytoskeleton is required as axons can range up to a meter

Question 15

What are the 4 morphological subtypes of neurons?

Answer 15

• Pseudounipolar
• Bipolar
• Golgi type I multipolar - longer axons than type II
• Golgi type II multipolar

Question 16

What happens when the axon is damaged during multiple sclerosis?

Answer 16

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

Question 17

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

Answer 17

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

They closely interact with blood vessels - ordered arrangement, interface with micovasculature

Question 18

What are the two types of oligodendrocyte?

Answer 18

Interfascicular and Perineuronal

Question 19

Give two myelin disease states.

Answer 19

Adrenoleukodystrophy

Multiple Sclerosis

Question 20

List the main classes of neuroglia

Answer 20

Oligodendroglia
Microglia
Astroglia
Eoendymal cells
Schwann cells (PNS)
Satellite glia (PNS)
Immature progenitors

Question 21

What is the role of microglia?

Answer 21

They are the immune cells of the CNS - resident macrophages

Derived from bone marrow

Question 22

What is myelin?

Answer 22

A lipid-rich insulating membrane

Question 23

What do ependymal cells do?

Answer 23

Produce CSF

Line ventricles and spinal cord

Question 24

Where and what are satellite cells?

Answer 24

In the PNS

Function like astrocytes

Question 25

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

Answer 25

In the grey matter
Type I - pyramidal cells of cerebral cortex, purkinje cells of cerebellum
Type II - stellate cells of cerebral cortex and cerebellum