L3 Cells Of The Nervous System Pt 2

Question 1

How can we classify neurons?

Answer 1

By structure:
- Number of neurites
- Dendritic geometry
- Connections
- Axon length

By gene expression:
- Underlies structural differences
- Defines neurotransmitter expression

Question 2

What are the types of neurites by number?

Answer 2

1. Unipolar
2. Bipolar
3. Multipolar

Question 3

If you wanted to find out the density of neurons in a given brain area which technique would you use?

Answer 3

Nissl staining

Question 4

What is the difference between unipolar and pseudo unipolar?

Answer 4

Unipolar neuron has 2 branches into 1 dendrite and 1 axon

Pseudo unipolar divides into 2 axons. One goes to the spinal cord, and the other goes to the periphery of the body

Question 5

What does the term ganglion mean?

Answer 5

A ganglion is a collection of neuron cell bodies located outside the central nervous system. They are found in the peripheral nervous system

Question 6

What is the highly specialised function of bipolar neurites?

Answer 6

They have a small area for recieving synaptic input which leads to reliable relay of information.

Question 7

What is a bipolar neuron?

Answer 7

Bipolar neuron has two processes extending from it: one axon and one dendrite. The axon is the process that transmits signals to other neurons, and the dendrite is the process that receives signals from others neurons

Question 8

Where are bipolar neurons generally found?

Answer 8

Found in the retina of the eye

Question 9

Give me 3 features of multipolar neuron

Answer 9

• Majority of neurons in the brain
• Large area for receiving synaptic input
• High levels of convergence

Question 10

Give me 2 examples of other multipolar neurons

Answer 10

• Stellate
• Pyramidal neurons

Question 11

What are pyramidal neurons?

Answer 11

They have distinct dendritic domains that have different properties and receive input from distinct sources.

Question 12

What is a sensory neuron?

Answer 12

Also known as afferent neurons, are responsible for converting external stimuli into signals that the brain can interpret

Question 13

What is a motor neuron?

Answer 13

Motor neurons are vital for our ability to move, breathe, and perform essential bodily functions. They are the link between the nervous system and our muscles and glands.

Question 14

What are the 2 categories within interneuron?

Answer 14

• Relay or projection neurons (connect brain regions)
• Local interneurons
  (Short axons and process information in local circuits)

Question 15

Can glia proliferate throughout life?

Answer 15

Yes

Question 16

What are the 3 functions that can be performed by different types of glial cells?

Answer 16

• Homeostatic
• Myelinating
• Phagocytic

Question 17

Name the homeostatic glia cells of CNS and PNS.

Answer 17

CNS - Astrocytes
PNS - Satellite cells

Question 18

Which glial cells are responsible for homeostatic function ?

Answer 18

CNS - Astrocytes
PNS - Satellite cells
ENS - Enteric glia

Question 19

What glial cells are responsible for the function of myelinating?

Answer 19

CNS - Oligodendrocytes
PNS - Schwann cells

Question 20

What glial cells are responsible for the phagocytic function?

Answer 20

CNS - Microglia
PNS - Schwann cells & Macrophages

Question 21

What do astrocytes do? (5)

Answer 21

1. They control environment surrounding neurons.
2. They act as fuel suppliers
3. They buffer extracellular potassium
4. Form part of the blood brain barrier
5. Couple neuronal activity to blood supply

Question 22

Why do astrocytes act as fuel supplies?

Answer 22

They can take up glucose from the blood and convert it to lactate. Lactate is a fuel that neurons can use to generate ATP

Question 23

What is the end feet of the astrocytes?

Answer 23

They are close association with blood vessels allowing them facilitate the transport of nutrients from the blood to the brain tissue which can be ultimately used for ATP for neurons in lactate form

Question 24

What is the tripartite synapse?

Answer 24

Tripartite synapse expands on the traditional synapse (pre+postsynaptic membrane) by including the surrounding astrocyte

Question 25

What happens at the tripartite synapse?

Answer 25

• Terminates neurotransmitter activity
• Recycles neurotransmitters to presynaptic terminals

Question 26

Do astrocytes have receptors?

Answer 26

They have receptors.

Question 27

What are microglia?

Answer 27

They are a type of glial cells that are found in the central nervous system

Question 28

What is the role of microglia?

Answer 28

They have a key role in tissue surveillance and phagocytosis

They can also have harmful roles in neurodegeneration

Question 29

What is the difference between oligodendrocytes and shwann cells?

Answer 29

Oligodendrocytes myelinate multiple neuron - axons.
Schwann cell myelinate a single neuron - axon.

Question 30

What are oligodendrocytes?

Answer 30

They are a type of glial cell that are responsible for producing myelin sheaths of CNS axons

Can have 15-30 processes from cell body to myelin sheaths

Question 31

What do Schwann cells do?

Answer 31

They form myelin sheath of PMS

One Schwann cell provides one myelin segment to a single axon

Question 32

Describe the formation of the myelin sheath

Answer 32

Process of oligo cytoplasms wraps many times around the axons
Cytoplasm squeezed out of layers by compaction

Myelin sheath maintains contact with glial cells for nourishment

Imagine a swiss roll.

Question 33

What is the function of myelin?

Answer 33

It’s primary function is to increase the speed of nerve impulse transmission

Question 34

How does the myelin sheath increase the speed of impulse transmission?

Answer 34

1) Myelin acts as an eletrical insulator which wraps around the axon, preventing the leakage of ions across the axonal membrane

2) Gaps in the sheath called Nodes of Ranvier are essential for generating action potentials

3) Insulation provided allows current to ‘jump’ rapidly from one node to the next - saltatory conduction