The Role of Neurones and Glia Flashcards
What is the nervous system composed of?
A network of neurones with supporting glia
What is the function of neurones in the nervous system?
They sense changes and communicate with other neurones
How many neurones are there in the central nervous system?
Around 1011
What is the function of glia in the central nervous system?
Support, nourish, and insulate neurones, and remove ‘waste’
How many glia are there in the CNS?
Around 1012
What are the types of glial cells?
- Astrocytes
- Oligodendrocytes
- Microglia
What is the most abundant type of glial cell?
Astrocytes
What is the role of astrocytes?
- Structural support
- Help to provide nutrition for neurones
- Remove neurotransmitters
- Maintain ionic environment
- Help to form the blood brain barrier
Where is the control of the concentration of neurotransmitters by astrocytes particularly important?
Glutamate
Why is the control of the concentration of glutamate particularly important?
Because it is toxic
How are astrocytes involved in maintaining an ionic environment?
K+ buffering
Why are astrocytes needed to help provide energy from neurones?
Because neurones do not store or produce glycogen
How do astrocytes help provide energy for neurones?
They produce lactate, which can be transferred to neurones via the glucose lactate shuttle, which supplements the neurones supply of glucose
What facilitates the astrocytes function of removing neurotransmitters?
They have transporters for transmitters, such as for glutamate
What can high levels of neuronal activity lead to?
A rise in [K+] in brain ECF
What are oligodendrocytes responsible for?
Myelinating axons in the CNS
What is responsible for myelinating axons in the PNS?
Schwann cells
What kind of cells are microglia?
Immunocompetent cells
How do microglia act as immunocompetent cells?
They recognise foregin material to activate, and them perform phagocytosis to remove debris and foreign material
What is the function of the blood brain barrier?
It limits the diffusion of substances from the blood to the brain extracellular fluid, and maintains the correct environment for neurones
Describe the structure of brain capillaries
- Tight junctions between endothelial cells
- Basement membrane surrounding the capillary
- End feet of astrocyte processes
What substances can be transported across the BBB?
Glucose, amino acids, and potassium
What does the ability to transport certain substances across the BBB allow?
Allows for the concentration to be controlled
In terms of transplant, what is the significance of the immune privileged status of the CNS?
It does not undergo rapid rejection of allografts
Why is it important that inflammatory reactions do not occur in the CNS?
The rigid skull will not tolerate volume expansion, and so too much inflammatory response would be harmful
How does the CNS prevent inflammatory responses from occuring?
The CNS inhibits the initiation of pro-inflammatory T-cell responses
How is the CNS immune protected?
- Microglia can act as antigen presenting cells
- T-cells can enter the CNS
Is the CNS isolated from the immune system?
No, immune privilege is not immune isolation, rather specialisation
