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 neurites?

Answer 2

Refers to any projections from the soma of a neuron.

Question 3

What are the types of neurites by number?

Answer 3

1. Unipolar
2. Bipolar
3. Multipolar
4. Pseudo unipolar

Question 4

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

Answer 4

Nissl staining

Question 5

What is the difference between unipolar and pseudo unipolar?

Answer 5

Unipolar- a single process extending from cell body.

Pseudo unipolar - it has a single projection but each end branches out into something different. e.g. CNS or muscles

Question 6

What is a bipolar neuron?

Answer 6

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 7

Where are bipolar neurons generally found?

Answer 7

Found in the retina of the eye

Question 8

Give me 3 features of multipolar neuron

Answer 8

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

Question 9

Give me 2 examples of other multipolar neurons

Answer 9

• Stellate
• Pyramidal neurons

Question 10

What is a sensory neuron?

Answer 10

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

Question 11

What is a motor neuron?

Answer 11

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 12

What are the 2 categories within interneuron?

Answer 12

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

Question 13

Can glia proliferate throughout life?

Answer 13

Yes

Question 14

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

Answer 14

• Homeostatic
• Myelinating
• Phagocytic

Question 15

Name the homeostatic glia cells of CNS and PNS.

Answer 15

CNS - Astrocytes
PNS - Satellite cells

Question 16

Which glial cells are responsible for homeostatic function ?

Answer 16

CNS - Astrocytes
PNS - Satellite cells
ENS - Enteric glia

Question 17

What glial cells are responsible for the function of myelinating?

Answer 17

CNS - Oligodendrocytes
PNS - Schwann cells

Question 18

What glial cells are responsible for the phagocytic function?

Answer 18

CNS - Microglia
PNS - Schwann cells & Macrophages

Question 19

What do astrocytes do? (5)

Answer 19

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 20

Why do astrocytes act as fuel supplies?

Answer 20

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 21

What is the end feet of the astrocytes?

Answer 21

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 22

What is the tripartite synapse?

Answer 22

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

Question 23

What happens at the tripartite synapse?

Answer 23

• Terminates neurotransmitter activity
• Recycles neurotransmitters to presynaptic terminals

Question 24

Do astrocytes have receptors?

Answer 24

They have receptors.

Question 25

What are microglia?

Answer 25

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

Question 26

What is the role of microglia?

Answer 26

They have a key role in tissue surveillance and phagocytosis They can also have harmful roles in neurodegeneration

Question 27

What is the difference between oligodendrocytes and shwann cells?

Answer 27

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

Question 28

What are oligodendrocytes?

Answer 28

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 29

What do Schwann cells do?

Answer 29

They form myelin sheath of PNS One Schwann cell provides one myelin segment to a single axon

Question 30

Describe the formation of the myelin sheath

Answer 30

Process of oligo dendrocytes wraps many times around the axons Cytoplasm squeezed out of layers by compaction Myelin sheath maintains contact with glial cells for nourishment ## Footnote Imagine a swiss roll.

Question 31

What is the function of myelin?

Answer 31

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

Question 32

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

Answer 32

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

Question 33

Give me an example of a unipolar neuron

Answer 33

Dorsal root ganglion