Cells of the Nervous System

Question 1

What are the protrusions coming out of dendrites called?

Answer 1

Dendritic spines

• These receive the majority of synapses
• Dendritic spines can have multiple synapses e.g. over 80,000 spines per cell

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

what type of cells do you have lots of in the cerebellum

Answer 3

Purkinje cells

Question 4

Where do axons originate?

Answer 4

Axon hillock

Question 5

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

Answer 5

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

Question 6

Describe the cytoskeleton of axons.

Answer 6

They have abundant intermediate filaments (needed for tensile strength )and microtubules and neurofilaments.

Question 7

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

Answer 7

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 8

What are the two forms of axon terminal?

Answer 8

Butons and Varicosities

Question 9

Where are varicosities found?

Answer 9

Along smooth muscle where one axon will stimulate the contraction of several smooth muscle cells
- Sometimes axons will synapse with many smooth muscle cells as it passes so you have multiple swellings containing neurotransmitter called varicosities

Question 10

What are the three arrangements of axons?

Answer 10

Axo-axonic: often modulatory
Axo-somatic: often inhibitory
Axo-dendritic: often excitatory

Question 11

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

Answer 11

Vesicles of neurotransmitter are carried along microtubules
These microtubules are unidirectional because the microtubules are polarised. There is retrograde transport(moving vesicles containing various molecules back to the cell body) but that occurs along other unidirectional microtubules.

Question 12

What happens when the axon is damaged during multiple sclerosis?

Answer 12

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

Question 13

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

Answer 13

Type 1 has long axons whereas Type II have short axons

Question 14

What are some features of the synapses?

Answer 14

Abundant mitchondria: lots of energy needed for ion pumping and synaptic transmission, therefore synpase is sensitive to oxygen deprivation.

• can be either inhibitory or excitatory
• competing inputs are integrated in the postsynaptic neurone-NEURONAL INTEGRATION

Question 15

what is pseudounipolar neurone

Answer 15

Pseudounipolar:

• tend to be sensory
• have 2 fused processes which are axonal in structure
• signal recieved goes straight axon terminal without going through soma

Question 16

where is bipolar neurones found

Answer 16

involved in the white matter of the cerebral cortex

Question 17

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

Answer 17

Astrocytes -

• star shape
• they are the support cells of the central nervous system
• numerous Intermediate filaments bundles in the cytoplasm of fibrous astroglia
• 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 18

What are the two types of oligodendrocyte?

Answer 18

Interfascicular and Perineuronal

Myelin forming cells of the CNS

Question 19

Give two myelin disease states.

Answer 19

1. Multiple Sclerosis (loss of myelin due to autoimmune reaction)
2. Adrenoleukodystrophy (leads to progressive loss of myelin)

Question 20

What is the role of microglia?

How do microglial cells change as they respond to a change?

Answer 20

They are the immune cells of the CNS.

• Cell shape changes and if the stimulus is strong enough it becomes phagocytic
• MS - microglial cells could be the ones destroying the myelin sheath

Question 21

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

Answer 21

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 22

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

Answer 22

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 23

What is the normal morphology of sensory neurones?

Answer 23

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

Question 24

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

Answer 24

Dendritic - excitatory
Somatic - inhibitory
Axonic - modulatory

Question 25

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

Answer 25

Grays Type I = vesicles are clear and rounded - EXCITATORY

Grays Type II = vesicles are oval or flattened - INHIBITORY

Question 26

What are the subtypes of astroglia?

Answer 26

Fibrous astrocytes
Protoplasmic astrocytes
Radial glia

Question 27

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

Answer 27

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

schwann cells:
Myelin producing cells of the PNS:
promote axon regeneration.

Question 28

What is multiple sclerosis

Answer 28

• A chronic inflammatory disease of the central nervous system of unknown cause causing oligodendroglial and axonal pathology
• Typically affecting young adults with relapsing – remitting pattern or chronic progressive evolution

Question 29

How to diagnose Multiple sclerosis

Answer 29

• Cerebrospinal fluid (CSF) analysis typically shows indices of inflammation
• MRI demonstrates characteristic lesions in CNS white matter (high signal = bright spots
• Primarily based on clinical history

Question 30

Pathophysiology of Multiple sclerosis?

Answer 30

-Cause unknown

– Inflammation and loss of myelin in the CNS

Question 31

Why do axons include intermediate filaments?

Answer 31

Needed for tensile strength as the cells can be very long