Lecture 1: Cellular Components

Question 1

What are the different types of glia?

Answer 1

1. Oligodendrocytes
2. Microglia
3. Astrocytes
4. Ependymal cells
5. Radial glia

Question 2

How are Neurones classified?

Answer 2

1. Structurally/Morphologically: Unipolar, Bipolar, or Multipolar neurones
2. Location: eg. Cortical pyramidal cells as they are found in the cortex

Phenotypically

1. Functionally: Sensory, motor, or interneurons, based on the direction of signal transmission and their role in the nervous system.
2. Chemical: What type of neurotransmitters do they use to communicate with other cells.

Question 3

What are the properties Neurones?

Answer 3

Excitability: They can respond to stimuli by generating an electrical signal.

Conductivity: Transmit signals over long distances through their processes.

Release Neurotransmitters: Allows them to communicate with other Neurones and cells.

Plasticity: Undergo structural and functional changes.

Question 4

What does the functional phenotype of a neurone describe?

Answer 4

The functional phenotype of a neuron is like a “personality” for the neuron - it describes how the neuron behaves and what it does in the nervous system.

e.g. motor neurone which excites skeletal muscle cells for motor function

Question 5

What are different types of functional phenotype?

Answer 5

motor neurone, excitatory neurone

Question 6

How can the functional phenotype of a neurone be identified?

Answer 6

• Electrophysiologically (measuring and directly recording the activity)
• Observing the effect of exciting the neurone, i.e. What effect does exciting the neurone have on the synaptic target.

Question 7

What does the chemical phenotype of a neurone describe?

Answer 7

which neurotransmitter is produced by the neurone e.g. acetylcholine (cholinergic neurone)

Question 8

How can the chemical phenotype of a neurone be identified?

Answer 8

• Direct labelling (immunohistochemistry)
• mRNA (in situ hybridisation)
• Genetic markers

Question 9

What are the most essential parts of a neurone

Answer 9

1. Dendrites
2. Cell body/Soma
3. Axon hillock
4. Axon
5. Synapse

Question 10

How does information flow occur in neurones?

Answer 10

Dendrites -> Cell body -> Axon

Question 11

What is the role of the cell body of a neurone?

Answer 11

information is integrated and sent out through the axon

Question 12

What are synaptic processes?

Answer 12

communication between neurones, can be axo-dendritic and axo-somatic

Question 13

What is myelin characterised by?

Answer 13

specialised properties for electrical conduction

Question 14

Are there more neurones or glia in the nervous system?

Answer 14

there are more glia in the nervous system

Question 15

What is the role of satellite cells?

Answer 15

supports cell bodies

Question 16

What is the role of Schwann cells (PNS) and oligodendrocytes (CNS)?

Answer 16

forms myelin sheaths

Question 17

What is the role of microglia?

Answer 17

1.Immune cells found in the central nervous system.
2. Monitor the brain for damage, infection, and abnormal activity.
3. Can engulf and destroy harmful substances through phagocytosis.
4. They release cytokines and other molecules to recruit other immune cells to the site of injury or infection.
5. Help to shape the developing brain by removing weak or unnecessary synapses.

Question 18

What is the role of ependymal cells?

Answer 18

Ependymal cells produce and circulate cerebrospinal fluid in the central nervous system.

Question 19

What is the role of astrocytes?

Answer 19

1. Involved in NT uptake as they have glutamate transporters
2. Possess an array of ion transporters to clean up extracellular spaces between neurones (Extracellular homeostasis)
3. Regulate local micro-vasculature and blood flow
   important for the BBB
4. Release Gliotransmitters
5. Help maintain the integrity of the blood brain barrier

Question 20

Why do astrocytes depolarise after neurones?

Answer 20

levels of extracellular potassium increases dramatically following the depolarisation of neurones and is taken up by astrocytes which become activated

Question 21

Why don’t astrocytes suffer from potassium toxicity?

Answer 21

• Astrocytes are connected to each other by channels called gap junctions.
• Gap junctions allow potassium to move between astrocytes.
• If one astrocyte has too much potassium, it can move through the gap junctions to another astrocyte with less potassium.

Question 22

Why do arterioles dilate as neural activity increases?

Answer 22

activation of neurones results in increased metabolic demand, producing metabolic waste which needs to be excreted.

Question 23

What is the role of astrocytic end-feet?

Answer 23

• Astrocytic end-feet help regulate blood flow in the brain
• They control the diameter of blood vessels they wrap around
• They aid in moving nutrients and waste products between blood vessels and brain cells to keep the brain healthy

Question 24

What are tripartite synapses?

Answer 24

Astrocytic foot processes contact both pre- and post-synaptic areas

Question 25

What are Gliotransmitters?

Answer 25

Chemical transmitters released by astrocytes -> not only are they passive cleaners but astrocytes actively participate in cellular communication in the brain

Question 26

What stimulates the release of gliotransmitters?

Answer 26

1. Increased activity in adjacent neurones and astrocytes
2. Increased [Ca2+] in astrocyte
3. Release Gliotransmitters (e.g. glutamate, ATP)

Question 27

What are characteristics of a neural circuit?

Answer 27

essential for complex functions, output varies depending on constituent components

Question 28

What is the functional phenotype of a neurone usually determined by?

Answer 28

the NT released -> effect on post-synaptic receptor (however exact effect of NT can depend on the post-synaptic receptor esp. GPCRs)

Question 29

What is a convergent circuit?

Answer 29

when multiple neurones send axons to a single neurone

Question 30

What is a divergent circuit?

Answer 30

when a neurone sends axons to multiple neurones

Question 31

What are different types of circuits?

Answer 31

convergent, divergent, feedback, lateral excitation, feedforward inhibition, feedback inhibition and disinhibition

Question 32

How was the Cholinergic Motor Neurone named?

Answer 32

Functional phenotype: Motor Neurone
Chemical Phenotype: Acetylcholine, thus it became Cholinergic

Question 33

What is glutamate?

Answer 33

Glutamate is a neurotransmitter that is released into the synaptic cleft when a neuron fires.

Question 34

What happens when there is excess glutamate in the synaptic cleft?

Answer 34

Excess glutamate in the synaptic cleft can lead to excitotoxicity and damage to the postsynaptic neuron.

Question 35

What is glutamate uptake?

Answer 35

Glutamate uptake is the process by which astrocytes take up excess glutamate from the synaptic cleft and convert it into a non-toxic form.

Question 36

What is excitotoxicity?

Answer 36

Excitotoxicity is a process that occurs when there is excessive stimulation of neurons by the neurotransmitter glutamate, leading to the over-activation of excitatory receptors on the postsynaptic neuron and subsequent damage or death of the neuron.

Question 37

What is extracellular ion homeostasis?

Answer 37

Extracellular ion homeostasis is the maintenance of a balance of ions, such as sodium, potassium, and calcium, outside of cells in the body. Astrocytes are involved in the process.

Question 38

What is the role of astrocytes in the neurovascular unit?

Answer 38

1. Astrocytes regulate blood flow
2. Maintain the blood-brain barrier
3. Provide nutrients to neurones
4. Regulate ion homeostasis.