Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ANAT 242 > L12 (C4) > Flashcards

L12 (C4) Flashcards

1
Q

how many glia are there per neuron

A

1-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Glial cells outnumber neurons in the human brain

Involved in almost all neural functions. what are some of these functions

A

Brain metabolism

Neuronal survival

Modulate synaptic activity

Communication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the key characteristics of neurons

A

they are excitable cells used for communication

there are 10^11 neurons and 10^14 synapses

they are post mitotic (meaning the neurons we had at birth we will have at death

they have a high metabolic rate (which is supported by glia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the key characteristics of glia

A

they are not excitable however they can be stimulated by Ca in astrocytes

they main role is support, nutrition and glue but they can communicate with themselves and other neurons

there are 10x more glia than neurons and they make up 50% of the brains volume

they undergo mitosis (regenerate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what do glia NOT have than neurons do

A

No chemical synapses,
action potentials,
neurotransmitters

but hey do have glial transmitters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does oligodendrocytes mean

A

Greek: Oligos=few; Dendron= tree

tree like structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the main role of oligodendrocytes

A

myelination and metabolic support

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are satellite oligodendrocytes

A

they are considered to be part of the gray matter whereas myelinated oligodendrocytes are part of the white matter

their role is to support metabolic function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how can the processes of the oligodendrocytes be recognised and distinguished from the
profiles of axons,

A

by their electron dense cytoplasm and their closely packed

microtubules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the process of myelination

the order in which things get myelinated

A

15 - 16 months we have full milination

16 weeks is the starts of milneation

4-6 is he formation of the corpus callosum

Anterior cerebral hemispheres 7 -10 months

Occipital 9-12 months

Parietal 9-12

Temporal lobe 11-14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what was a key driver in evolution

A

myelination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the 4 reasons why myelination is an evolutionary advantage

A
  1. Myelination strongly reduces energy consumption
  2. Rapid impulse propagation/increased conduction velocity
  3. Muscle control
  4. Neurotrophic contribution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how is neurotrophic contribution an evolutionary advantage

A

required for the long-term integrity and survival of axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is muscle control an evolutionary advantage

A

became the basis for the development of complex predatory
and escape behaviour, which ultimately drove body size and vertebrate evolution

This means that we would be able to run faster/respond faster from things that were trying to kill us

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how is rapid impulse propagation/increased conduction velocity an evolutionary advantage

A

allowed complex yet compact higher nervous systems to evolve.

makes APs 10x faster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how is myelination strongly reduces energy consumption an evolutionary advantage

A

action potentials and ion currents are restricted to less than 0.5% of the axon’s surface.

Myelin strongly reduces energy consumption because it is all focused at one point which also allows for rapid propagation and conduct velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the difference between myelinated axons in the CNS and the PNS

A

In the CNS this is the oligodendrocytes. One oligo can myelinate multiple internodes

The swann cells in the PNS only myenate one segment of one neuron

Therefore in the CNS myelination happens around more than one axon and in the PNS a schwann cell will only go around one but can be associated with many

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

why are very thin axons unmyelinated

A

In order to be myelinated the acon needs to have a diameter more than 1um because otherwise it won’t have an effect. Therefore small axons won’t be myelinated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

naked axons are found where

A

in the CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

why are unmyelinated axons in the CNS referred to as naked but unmyelinated in the PNS are not

A

In the PNS unmyelinated are still surrounded by membrane of the schwann cell. This is because thee swann cell needs to protect the axon therefore its membrane, although it is not completely covering it, they are associated

NOTE: PNS schwann cells are associated with many axons but you don’t completely encase the axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

why is it adventitious in the PNS to have schwann cells associated with many neurons

A

This is adventitious in the PNS as if one swann cell dies then it will only effect on axon where as in the CNS it will effect multiple

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

describe the structure of an oligodendrocyte

A

There is a inner cytoplasmic and a outer cytoplasmic ridge

When you cut away the myelin you can see that it comes in a bit in the nodes. This part is called the parra node

Oligodendrocytes have a wide reach

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what causes myeline gene expression

A

NRG 1 type 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

how does NRG 1 type 3 cause myelin gene expression

A

When NRG 1 type 3 is expressed in the axon and when it recognised that then it starts a signal cascade cascade which causes myelin gene expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the inner and the outer part of the myelin called

A

The inner mesaxon is the inner part of the membrane and the otter mesaxon is the outer part

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is important about the myelins thickness

A

The bigger the diameter the bragger the myelin sheath

if there are issues with the thickness it means means that there is a problem with that axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is the g ratio (thickness) for myelin wrapping

A

0.6 - 0.7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is the equation for g ratio

A

g ratio = d/D

d = axon diameter

D = axon + myelin diameter

29
Q

is remyelination of an axon possible

A

yes but the remyelination will never be as thick as it originally was

30
Q

describe the process of lateral radial wrapping in oligodendrocyte myelination

A

The oligodendrocyte has a precursor cell

When it starts growing then it makes more plasma membrane and starts to ensheath the axon. It rolls around it. When it grows it gets wider and longer, this is lateral radial wrapping

While the wapping is happening then the channels become clustered in the nodes

The smitlansion incisures or clefts and these are the cytoplasmic channels which are there to deliver the proteins needed

You then have created the nodes

The incisures close but the incisures around the cleft are still there so it is able to keep growing if it is needed

31
Q

what are The smitlansion incisures or clefts

A

The smitlansion incisures or clefts and these are the cytoplasmic channels which are there to deliver the proteins needed

32
Q

what is the difference between oligodendrocyte and schwann cell myelination

A

oligodendrocytes have one extension which wrapps one part of one axon for many axons

Whereas schwann cells wrap one part of one axon

33
Q

why do we need local protein synthesis in the oligodendrocytes

A

synthesis of myelin proteins needs to happen distal

to the cell body

34
Q

what is needed for local protein synthesis to take place in the oligodendrocytes

A

microtubule based transport takes RNA granules that contain mRNA and ribosomes from the nucleus to the parranodes

35
Q

what is the major dense line

A

MDL is the 2 inner layer of plasma membrane – a tiny bit of cytoplasm

toothpaste tube and the little bit of toothpaste left inside

36
Q

what is the intraperiod line

A

IPL is the 2 outer layers of plasma membrane and ECS

the outside of the toothpaste tube and the space inbetween the layers

37
Q

what proteins stop the myelin sheath from unrolling

A

P0 protein zero (PNS) located from cytoplasm to extracellular space (across the membranes) where it will bind to another PO protein

MBP myelin basic protein (PNS/CNS) only in the cytoplasm

PMP 22 peripheral myelin protein (22kD)
(PNS) transmembrane protein

38
Q

describe the structure of the internodes

A

node -> paranodal region -> juxtaparanodal region -> internodeal region

39
Q

where are the stabilising proteins located in the internode

the ones that stop the myelin sliding along the axon

A

in the paranodal and juxtaparanodal regions

40
Q

what proteins stabilise the internode

the ones that stop the myelin sliding along the axon

A

NF155 - neurofascin – glial/axon cell adhesion molecule

Cntn/Cntn2 – contactin - cell adhesion – glial/axon

Caspr – transmembrane protein on axon – contactin-associated protein

41
Q

what is the role of casper NF155 and Cntn/Cntn2

A

seals periaxonal

space to outside

42
Q

what do we know about NF115

A

NF stands for neurofilament

I the parranode there is neurophassin this can be 155 or 165 as it is not just produced by the myelin sheath but also the axons

Therefor it goes through the space from the myelination and the axon to hold them together

43
Q

where is casper produced

A

Casper is produced in the paranodal regions and it binds to neurophassin

44
Q

what is casper associated with

A

Casper is also called contatic associated protein because they are always together and they bine to stabilise the paranodal section

At the juxtaparanodal region there are lots of different contactins and casper

45
Q

what does casper bind to

A

neurophassin

46
Q

what % of a myelinated axon is ensheathed in myelin

A

99%

47
Q

when does the axon use nodally sourced energy

A

Nodally sourced energy is for basal activity or small-diameter
myelinated axons with short internodes as they only fire at low frequencies.

48
Q

how will they get energy continually along the length of

internode or when demand increases?

A

through MCTs (monocarboxylate transporters )

these are extracellular
membrane channels which transport lactate, pyruvate, and ketone bodies, along with protons, down their concentration
gradient across membranes

49
Q

how many MCTs (monocarboxylate transporters ) do we know of

A

there are 14 or more

50
Q

how many MCTs (monocarboxylate transporters ) in the CNS

A

MCT1, 2 and 4 are in the CNS

51
Q

which MCTs (monocarboxylate transporters ) is located in oligodendrocytes

A

MCT1

52
Q

how do Oligodendrocytes uniquely provide metabolic support to neurons/axons

A

they carry molecules with one carboxylate group (monocarboxylates), e.g. lactate and pyruvate, across
biological membranes.

53
Q

where are MCT1 and 2 located and how does their location get energy into the axon

A

MCT1- oligo plasma membrane

MCT 2 - axon plasma membrane under
Myelin

This is about getting energy into the axon, it gets it from the outside of the oligodendrocyte and brings it into the paraxonal space (1) and then from the space into the axon (2)

54
Q

what is the principal

metabolic supplier of lactate to neurons an axons

A

oligodendrocytes

´Why is this important? Expression
of MCT1 reduced in motor
cortex of ALS patients
ALS = amyotrophic lateral sclerosis

55
Q

what is ALS

amyotrophic lateral sclerosis

A

Expression

of MCT1 reduced in motor cortex of ALS patients which causes issues with voluntary movement

56
Q

why do you want lactate in the oligodendrocytes

A

It can get latate from the blood or it can get glucose which it breaks down into lactate which is then converted to pyruvate by lactate dehydrogenase which is used by mitochondria for oxidative phosphorylation to make ATP

57
Q

how does glucose get into the oligodendrocyte

A

through GLUT

58
Q

what is the NMDA receptors role in the e metabolic supportive function of oligodendrocytes

A

The neuron releases glutamate into the synaptic cleft which binds to NMDA receptors on the oligodendrocyte which then sends a signal to transport lactate into the neurons

59
Q

what is the effect of excessive NMDA signaling

A

Deleterious (damaging) effect of excessive NMDA receptor signaling in
oligodendrocytes is now
confirmed to be closely related with demyelinating white matter diseases, such as cerebral palsy,
multiple sclerosis, schizophrenia,
and Alzheimer’s disease

60
Q

Multiple sclerosis
Guillain Barr syndrome (both autoimmune diseases) which involve disruption of myelin, loss of myelin. what does this cause

A

Changes in function (CNS and PNS)

Slowed nerve conduction because AP are not saltatory

this affects movement, bodily functions and causes loss of sensations, co-ordination, and balance

it also causes muscle weakness, difficulty with walking, Numbness and Visual disturbances

61
Q

what does Multiple sclerosis refer to

A

sclerosis = scars

Multiple sclerosis refers to scars (sclerae- known as plaques or lesions) particularly in the white matter of the brain and spinal cord

this is from the immune system targeting the myelin

62
Q

Multiple sclerosis causes…

A

Loss of oligodendrocytes, Microglia and Astrocytes

Degradation of myelin

Immune response- inflammatory response

63
Q

when does onset of MS usually happen

A

20-40s

64
Q

what is the initial cause of MS

A

Within the cellular system we have T cell which are not supposed to be in the brain.

Somehow they get into the brain

These express lots of cytokines which recruit other T cells and macrophages to attack

They also propagate they cycle of inflammation

It also causes the release of antibodies which means that the macrophage will attack the myelin sheath

65
Q

every clinical episode of MS how many new plaques will they develop

A

10

66
Q

what are some hypothesis for the cause of MS

A

people think that it could be from stress or about the latertude

Further away from the equator more common

67
Q

there are 3 stages to MS damage what are these

A
  1. lymphocyte driven inflammation
  2. microglia activation
  3. chronic tissue injury (astrocytic gliosis)
68
Q

what causes the microglia to be activated

A

the role of microglia are for inflammation and repair

at the start they removal of myelin debris and Promote remyelination

But: Chronic activation of microglia leads ultimately to neuronal loss in late stage (because of their inflammatory response)

ANAT 242 (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions