Week 5: T2 (1) Micro: cells of the brain

Question 1

What are glial cells?

Answer 1

Non-neuronal support cells of the nervous system. Also known as neuroglia or glia. About 90% of cells in the brain.

Question 2

What types of glial cells are there?

Answer 2

Astrocytes
Oligodendrocytes
Microglia
Ependymal cells

Question 3

What are the characteristics and functions of astrocytes?

Answer 3

Most abundant cell type in the brain.
They have ion channels and can communicate with one another.
1. Scaffolding, or structure network, for the brain.
2. Help maintain the blood-brain barrier, thus protecting the brain from infection and bacteria.
3. Have ‘foot processes,’ which are physical structures that are built onto the blood vessels and maintain the integrity of the structure.
4. Help maintain the microenvironement around neurons.
5. Help mop up or recycle neurotransmitters such as glutamate.
6. Help form glial scars, a form of repair after brain injuries.

Question 4

What is the blood-brain barrier?

Answer 4

The blood-brain barrier is a tight junction around blood vessels that go into the brain.

Question 5

What are “foot Processes”

Answer 5

Physical structures of astrocytes which are built onto the blood vessel and maintain the structure.

Question 6

How do astrocytes maintain the microenvironment around neurons?

Answer 6

1. They mopping up different irons such as potassium which is released when neurons depolarize.
2. Help mop up neurotransmitters/recycle neurotransmitters such as glutamate which if abundant might be toxic.
   This is also “physiological support” = recycle the small spheres of orange neurotransmitter. in the diagram.

Question 7

What are endothelium?

Answer 7

Blood vessel walls. It is supported by astrocytes.

Question 8

What are oligodendrocytes and what are their characteristics?

Answer 8

1. A type of glial cell in the brain that
   ‘Myelinate’ axons
2. In utero, wrap around axon in concentric lamellae
3. Largely finished after first year
4. Not complete until ~20 years old,
5. Especially associated with PFC cortices: individuals are more prone to damage during this time.
6. Myelination makes neurotransmission 20-50 times faster.

Question 9

What is myeline, what is it used for, and what is its characteristics?

Answer 9

1. A wrap a fatty layer around the axon that helps insulate it.
2. It stops cross-conduction.
3. It speeds up conduction of transmission along neurons.
4. Begins when foetus and gradually wraps fatty layers around the axon throughout life.
5. Mostly done by 1 year, but PFC until 20 years of age.

Question 10

What are microglia and what are their characteristics?

Answer 10

Glial cells.

1. A type of macrophage found only in the brain.
2. Occur amongst neurons.
3. Found also in blood vessels in the brain.
4. Found in the meninges that surrounds the brain.
5. In utero, help clear waste material.
6. Important in apoptosis.
7. highly immunosuppressed

Question 11

What are macrophages?

Answer 11

Type of white blood cells that engulf, digest, and kill anything that’s recognized as foreign within the body; a process without antibodies (immunoglobulin protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses).

Question 12

What is apoptosis?

Answer 12

A programmed cell death.

Question 13

What type of glial cell is immunosuppressed, and what does it mean?

Answer 13

Microglia cells are immunosuppressed. It means that they are only activated in response to a particular immune conditions such as an infection.

Question 14

What are ependymal cells?

Answer 14

1. They line the ventricles (the ventricles of the brain are a communicating network of cavities filled with cerebrospinal fluid (CSF) and located within the brain parenchyma, i.e., the functional tissue in the brain that is made up of the two types of brain cell, neurons and glial cells.
2. They secrete and absorb cerebrospinal fluid that helps support and buffer the brain.

Question 15

What are neurons?

Answer 15

1. Electrically excitable cells.
2. Collect chemical information via their dendrites
   a. All neurons have receptors for glutamate and GABA.
   b. Have a dendritic tree which collects information.
3. Constitute 10% of brain cells
   Specialized ion pumps establish an electrical gradient
4. neuronal membranes are polarized (charged) and depolarize spontaneously, but this can be stimulated and inhibited
5. Neurons are named according to their output Neurotransmitter.

Question 16

What is glutamate

Answer 16

The main excitatory neurotransmitter in the brain; it is important for ionotropic transmission; it makes neurons fire. It is also an amino acid, i.e., a basic constituent of protein.
The main excitatory neurotransmitter in the brain; it makes neurons fire; ubiquitous ‘go’ signal in the brain. It binds to neurons, opens ion channel that makes the neuron more polarized and more likely to fire.

Question 17

What is GABA

Answer 17

An inhibitory neurotransmitter in the brain; it stops neurons from firing. It opens pores that lets different ions in that makes the neuron more stable.

Question 18

What is dendritic tree?

Answer 18

1. Part of the neuron, a receptor, grows out of the top of the neuron and collects information.
2. It is covered with receptors of different types, depending on the location in the brain.
3. Various receptors bind specific neurotransmitters, primarily ionotopric NTs, but also metabotropic NTs and neurohormonal molecules.

Question 19

What is a soma?

Answer 19

The cell body of a neuron. Also named perikaryon. It assimilates all the information.
Assimilates metabortropic input (NTs such as serotonin, dopamine, acetylcholine) & neurohormonal input (ex. cortisol).

Question 20

What is a perikaryon?

Answer 20

the cell body of a neuron; soma. peri=around, karyon = nutneurotransmitters

Question 21

What is a neurotransmitter and what are common types of neurotransmitters?

Answer 21

A (chemical agent) substance that is released from the axon terminal of a presynaptic neuron on excitation, and that travels across the synaptic cleft to either excite or inhibit the target cell.
Serotonin
Dopamin
Acetylcholine

Question 22

What are common types of neurohormonal inputs?

Answer 22

Cortisol

Question 23

What is ionotropic

Answer 23

Electrical charge. Electrical charge of a neuron can be altered by information that is assimilated in the cell body (soma; perikaryon).
Ionotropic transmission opens pores in the cell that make it more or less excitable, more or less electrically charged.

Question 24

How is internal cellular functioning?

Answer 24

metatabolic and neurohormonl function of the soma (cell body; perikaryon).

Question 25

What is depolarization?

Answer 25

Firing of a neuron. It depends of the summation of the information assimilated in the soma. The current travels along the axon.

Question 26

What are ions?

Answer 26

Ions are molecules that move in and out of neurons and make them more of less charged.

Question 27

Which basic neurotransmitters are involved in iontropic transmission?

Answer 27

Glutamate and GABA

Question 28

Which basic neurotransmitters are involved in iontropic transmission?

Answer 28

Glutamate and GABA. The continuous binding of GABA and glutamate makes neurons more or less excitable.

Question 29

What is Dale’s Law?

Answer 29

Incomplete. Schematically, whatever type of input a neuron receives, it only releases one type of output

Question 30

What change in GABA and glutamate occurs across life?

Answer 30

The ratio between the two. Between ages 15 and 20 there are large changes when there is a reduction in glutamate, and an increase in GABA , i.e., pruning.

Question 31

What happened in psychosis?

Answer 31

There is a difference in the ratio of inhibitory and excitatory synapses in comparison with “normal” state.
There is a deficient myelination.

Question 32

What is a synapse?

Answer 32

A junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.

Question 33

What do GABA and glutamate have in common?

Answer 33

Both are neurotransmitters. These are amino acids, which are a Amino acids but GABA is not an alpha amino acid and cannot incorporate into protein.