The Role of Neurones and Glia

Question 1

What is the nervous system composed of?

Answer 1

A network of neurons with supporting glia

Question 2

What is the function of neurons in the nervous system?

Answer 2

They sense changes and communicate with other neurones

Question 3

How many neurones are there in the central nervous system?

Answer 3

Around 10¹¹

Question 4

What is the function of glia in the central nervous system?

Answer 4

Support, nourish, and insulate neurones, and remove ‘waste’

Question 5

How many glia are there in the CNS?

Answer 5

Around 10¹²

Question 6

What are the types of glial cells?

Answer 6

• Astrocytes
• Oligodendrocytes
• Microglia

Question 7

What is the most abundant type of glial cell?

Answer 7

Astrocytes

Question 8

What is the role of astrocytes?

Answer 8

• Structural support
• Help to provide nutrition for neurones
• Remove neurotransmitters
• Maintain ionic environment
• Help to form the blood brain barrier

Question 9

Where is the control of the concentration of neurotransmitters by astrocytes particularly important?

Answer 9

Glutamate

Question 10

Why is the control of the concentration of glutamate particularly important?

Answer 10

Because it is toxic

Question 11

How are astrocytes involved in maintaining an ionic environment?

Answer 11

K⁺ buffering

Question 12

Why are astrocytes needed to help provide energy from neurones?

Answer 12

Because neurones do not store or produce glycogen

Question 13

How do astrocytes help provide energy for neurones?

Answer 13

They produce lactate, which can be transferred to neurones via the glucose lactate shuttle, which supplements the neurones supply of glucose

Question 14

What facilitates the astrocytes function of removing neurotransmitters?

Answer 14

They have transporters for transmitters, such as for glutamate

Question 15

What can high levels of neuronal activity lead to?

Answer 15

A rise in [K⁺] in brain ECF

Question 16

What are oligodendrocytes responsible for?

Answer 16

Myelinating axons in the CNS

Question 17

What is responsible for myelinating axons in the PNS?

Answer 17

Schwann cells

Question 18

What kind of cells are microglia?

Answer 18

Immunocompetent cells

Question 19

How do microglia act as immunocompetent cells?

Answer 19

They recognise foregin material to activate, and them perform phagocytosis to remove debris and foreign material

Question 20

What is the function of the blood brain barrier?

Answer 20

It limits the diffusion of substances from the blood to the brain extracellular fluid, and maintains the correct environment for neurones

Question 21

Describe the structure of brain capillaries

Answer 21

• Tight junctions between endothelial cells
• Basement membrane surrounding the capillary
• End feet of astrocyte processes

Question 22

What substances can be transported across the BBB?

Answer 22

Glucose, amino acids, and potassium

Question 23

What does the ability to transport certain substances across the BBB allow?

Answer 23

Allows for the concentration to be controlled

Question 24

In terms of transplant, what is the significance of the immune privileged status of the CNS?

Answer 24

It does not undergo rapid rejection of allografts

Question 25

Why is it important that inflammatory reactions do not occur in the CNS?

Answer 25

The rigid skull will not tolerate volume expansion, and so too much inflammatory response would be harmful

Question 26

How does the CNS prevent inflammatory responses from occuring?

Answer 26

The CNS inhibits the initiation of pro-inflammatory T-cell responses

Question 27

How is the CNS immune protected?

Answer 27

• Microglia can act as antigen presenting cells
• T-cells can enter the CNS

Question 28

Is the CNS isolated from the immune system?

Answer 28

No, immune privilege is not immune isolation, rather specialisation