Oligodendrocytes And Other Myelinating Neuron And Slee

Question 1

What are oligodendrocytes?

Answer 1

Myelinating cell of the CNS. Myelinated multiple neurones.

Question 2

What is a schwann cell?

Answer 2

Myelinating cell of the PNS only myelinated one cell.

Question 3

What is G-ratio?

Answer 3

This is the interdependent relationship of radial growth:myelin sheath (lamellae number)

Question 4

What does it mean when Glia and axons are interdependent?

Answer 4

• if you lose the axon results in degeneration of oligdendrocytes and dedifferentiation of schwann cells.
• conversely axons degenerate in the absence of schwanna cells or oligodendrocytes

Question 5

What two types of schwann cells do you get?

Answer 5

Myelinating and unmyelinating

Question 6

What is the function of nonmyelinating schwann cell?

Answer 6

Surround bundles of small diameters, also provide support and isolation from myelinated axons.

Question 7

What markers do non-myelinating schwann cells express?

Answer 7

Express markers L1 and NCAM which aren’t found in myelinating schwann cell.

Question 8

What is the function of myelinating schwann cells?

Answer 8

They are perisynaptic glial cells that ensheath the synapse. They respond to synaptic activity through calcium waves. They are able to modulate synaptic activity by regulation of extracellular ion levels and receptor aggregation.

Question 9

What is an OBEC?

Answer 9

Olfactory bulb ensheathibg cell

Question 10

Where are OBECs located?

Answer 10

Located at the interphase of CNS and PNS.

Question 11

What are the functions of OBECs?

Answer 11

They phagocytose a zonal debris and dead cells

Also support and guide olfactory axons by secreting neurotrophic factors.

Question 12

What is the myelin sheath?

Answer 12

Fatty insulated layer that facilitates saltatory conduction. It separated by nodes of renvier.

Question 13

What’s a node of renvier?

Answer 13

These are the gaps in the myelin sheath.

Question 14

What’s the composition of myelin?

Answer 14

Lipids 70%

Protein 30%

Question 15

How many phases are there to myelination?

Answer 15

4 phases

Question 16

What is phase 1 of myelination?

Answer 16

Axon contact

Question 17

How does axon contact occur in myelination?

Answer 17

The axonal surface loses NCAM. Then tags axons with L1 to be myelinated. Then the contact of axons triggers OPCs to differentiate into oligodendrocytes

Question 18

What is phase 2 of myelination?

Answer 18

Axon ensheathment and internodal segements

Question 19

How does axon ensheathment and internodal segments happen?

Answer 19

Extension of initiator process spiral rounds axon. Myelinated man axons followed by remodelling.

Question 20

What is phase 3/4 of myelination?

Answer 20

Remodelling and maturation

Question 21

What happens during remodelling and maturation in myelination?

Answer 21

Subsequent wraps around axon produced fuse together using PLP and MBP proteins

Question 22

What happens in multiple sclerosis?

Answer 22

Immune system attacks CNS forming plaques and lesions. Also generate autoantibodies against myelin sheath- directly causing damage to oligodendrocytes.

Question 23

What happens to the BBB during multiple sclerosis?

Answer 23

BBB breaks down and drives entrance of immune cells (T-cells). Then demyelination by T-cells drive inflammation leading to swelling.

Question 24

What are the two different phases of sleep?

Answer 24

NREM & REM

Question 25

What do REM & NREM sleep stand for?

Answer 25

Rapid eye movement

Non-rapid eye movement

Question 26

What is NREM sleep?

Answer 26

This is sleep with reduced physiological activity but more parasympathetic activity.

Question 27

What is the sleep cycle?

Answer 27

REM sleep happens every 90-120 mins- most REM sleep occurs late at night.

Question 28

What is REM sleep?

Answer 28

This when dreaming occurs and resembles the awake state for brain activity heart rate and respiration.

Question 29

Why do we need sleep?

Answer 29

Otherwise it leads to inattention, slower computational speeds, impaired verbal fluency, learning issues and lower IQ (caused by sleep deprivation)

Question 30

What is narcolepsy?

Answer 30

Daytime sleepiness- can have sleep attacks ,sleep paralysis Can also have excessive dreaming and waking at night.

Question 31

What causes narcolepsy?

Answer 31

Orexin signalling defect

Question 32

What is sleep apnea?

Answer 32

Blocks airways causing risk of cardiovascular disease and death if untreated

Question 33

How does the molecular body clock work?

Answer 33

Heterodimeric TF clock,cycle bind to promoter called E box which turns in transcription of period and timeless genes.

Question 34

What happens to the Period protein in the molecular body clock?

Answer 34

Period can bind a kinase called double time, if period doesn’t bind double time (DBT) then it phosphorylase Period at site for ubiquination making it take more time to build up.

Question 35

What happens when period and timeless complex?

Answer 35

Form heterotrimer with DBT. At midnight enough is made it moves into the nucleus stopping binding of clock and cycle to promoter. This causes depletion of protein as it’s phosphorylated causing awakening.

Question 36

What is SCF mediated protein degradation?

Answer 36

Skip-Cul-F box mediated protein degradation.

Question 37

How does SCF-mediated protein degradation work?

Answer 37

Proteins E1,2,3 add ubiquitin proteins to substrate protein. Substrate protein is recognised by the F-box due to phosphorylation. Ubiquitous chain produced is recognised by 26s proteosome which does the degradation.?

Question 38

How is SCF-mediated light dependent degradation different?

Answer 38

Uses a molecule called CRY which is sensitive to blue light which causes conformational change allowing timeless binding. This allows kinase to phosphorylate timeless. Allowing ubiquination via same route as SCF