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Neuro > Homeostasis in the nervous system > Flashcards

Homeostasis in the nervous system Flashcards

1
Q

What is the neuronal microenvironment composed of ?

A

Glia
Capillaries
Neurons
Extracellular space

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2
Q

What is extracellular space composed of?

A

Extracellular matrix
Brain extracellular fluid (interstitial fluid)

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3
Q

What can uncontrolled neuronal influence of brain extracellular fluid lead to?

A

Neuronal dysfunction
Neuronal death

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4
Q

How can neuronal activity change the composition of the BECF?

A

Increase K+ conc
Changes in Ca+ conc
Changes in O2, glucose and CO2 conc
Increase in H+,, leading to acidifcation

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5
Q

How could a change in BECF composition change neuronal activity?

A

Increase in K+ conc can elevate resting potential
-> Brings the cell closer to ap firing potential, increasing neurotransmitter release

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6
Q

How is the neuronal microenvironment regulated?

A

Blood brain barrier
CSF in ventricular system
Neurons
Glial cells

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7
Q

How was the blood brain barrier identified?

A

Intravenous injection of dyes
- Dyes pass across leaky capillaries
- Stain soft tissue
- No staining in the brain

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8
Q

Why does the brain not get stained?

A

The capillaries are less leaky than those in the spinal cord

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9
Q

Function of brain blood barrier

A

Protect neurons from fluctuations in concentrations of substances in the blood

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10
Q

How is the brain blood barrier maintained?

A

Tight junctions between endothelial cells
Thick basement membrane
Astrocytic endfeet

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11
Q

How do endothelial cells maintain the brain blood barrier?

A

Prevents paracellular diffusion of materials

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12
Q

How does the thick basement membrane maintain the bbb?

A

Acts as a physical barrier

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13
Q

How do astrocytic end feet maintain the bbb?

A

Interact with blood vessels and form a capsule

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14
Q

What is the difference between an exchanger and a cotransporter?

A

Exchanger is in opposite directions, cotransporters are in the same direction

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15
Q

What molecules pass the bbb easily?

A

Small, uncharged or lipid soluble molecules

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16
Q

What is an example of a facilitated transporter in bbb?

A

Glut1

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17
Q

What is an example of an exchanger in bbb?

A

Na - H exchanger

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18
Q

Where is cerebrospinal fluid produced?

A

Choroid plexuses

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19
Q

What are the circumventricular organs function?

A

Form tight junctions (in the form of ependymal cells) beneath the blood vessels

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20
Q

Why are there leaky areas of the bbb?

A

To allow secretion of hormones
Osmoreceptors
Temperature control centres

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21
Q

Function of the ventricular system?

A

Increased buoyancy
Physical protection
Maintains appropriate level of ions
Removes waste products

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22
Q

How does the ventricular system increase the buoyancy of the brain?

A

The brain doesn’t move with full weight when moving around

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23
Q

What does the cerebral aqueduct lead to?

A

The 4th ventricle where it thins through the medulla and becomes the central canal

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24
Q

What is in CSF?

A

Electrolytes
Amino acids
Proteins
Osmolality

25
Q

What is exchanged between CSF and BECF?

A

Macronutrients
Micronutrients
Ions

26
Q

What is exchanged between BECF and CSF?

A

Metabolic waste products
Neurotransmitters

27
Q

What areas does the CSF circulate around?

A
  • 3rd ventricle
  • 4th ventricle
  • central canal
  • foramens
  • outer brain
  • sinuses
  • venus system
28
Q

What happens to CSF at the superior sagittal sinus?

A

CSF is absorbed from the subarachnoid space into the venous blood system

29
Q

How much CSF is produced a day?

A

500 mls

30
Q

What is an ependymal cell?

A

A specialised glial cell that line the ventricles

31
Q

What are the stages of CSF secretion?

A
  1. Ultrafiltration of plasma into ECF across normal ‘leaky’ capillaries
  2. Selective absorption of substances into csf across choroidal epithelial cells
  3. Free movement of substances from CSF to BECF across ependymal cells
32
Q

What are the 3 types of meninges?

A

Pia mater
Arachnoid mater
Dura mater

33
Q

Describe pia mater

A

Covers the surface of brain and blood vessels and allow diffusion between CSF and BECF

34
Q

Describe arachnoid mater

A

Cells linked by tight junctions preventing diffusion between CSF and plasma

35
Q

Describe dura mater

A

Thick inelastic membrane with 2 layers split to form intercranial sinuses
Prevents too much movement

36
Q

How do things enter the dura mater?

A

Arachnoid granulations push through dura mater

37
Q

What is the mechanism of csf absorption?

A

Arachnoid granulations push up through the dura matter into the venous sinus
- The csf is transported in vesicles driven by pressure build up

38
Q

What is hydrocephalus a result of ?

A

Dilation of ventricular system
Obstruction in ventricular system
Interrupted csf absorption

39
Q

What are the symptoms of hydrocephalus?

A

Increased intercranial pressure
Less of brain cells
Loss of brainstem reflexes

40
Q

Where do neurons and astrocytes terminate transmission?

A

Tripartite synapse

41
Q

How is neurotransmission terminated?

A

Neurotransmitters are removed from synaptic cleft and recycled
Via neurons and astrocytes

42
Q

How is glutamate neurotransmission terminated?

A

EEAT transports glutamate back into the cell for recycling
Astrocytes convert glutamate to glutamine

43
Q

What is the main excitatory neurotransmitter?

A

Glutamate

44
Q

What occurs if glutamate is left in the cleft?

A

Excitotoxicity

45
Q

How is K+ removed from extracellular space?

A

Astrocytes and neurons
Sodium potassium ATPase pump, moves against gradient back into the cell

46
Q

What happens when astrocytes sense high K+ in ECF?

A

Convert glucose into lactate to excite neurons

47
Q

How does extracellular K+ affect astrocyte function?

A

Astrocytes drive K+ into ECF
Can drive K+ to be taken up in the cell, increasing glucose metabolism
More glucose allows better K+ uptake via ATPases

48
Q

Why do neurons have a resting membrane potential of -65mV and glia have -85mV?

A

Neuronal membranes are more permeable to Na+ than astrocytic membranes
Astrocytes are more sensitive to extracellular K+ changes

49
Q

What creates a syncytium?

A

Astrocytes coupling to each other via gap junctions

50
Q

How is a gap junction formed?

A

Connexins form a connexon on 1 membrane
2 connexons in different membranes form a gap junction.

51
Q

What is spatial buffering?

A

Regulation of extracellular potassium concentration

52
Q

What is neurovascular coupling?

A

Neurons are coupled to vasculature

53
Q

Describe the process of neurovascular coupling

A

Increased neuron firing rate leads to an increase in astrocyte Ca2+ levels ->
Leads to a release of vasoactive substances from the astrocyte ->
Blood vessels and diameter change

54
Q

What do MRI allow imaging of ?

A

3d structural images of the brain

55
Q

What is the function of a PET scan?

A

Exploits the use of glucose

56
Q

What is the function of an fMRI scan?

A

Exploits the use of oxygen

57
Q

What is BOLD in terms of fMRI?

A

Blood
Oxygenation
Level
Dependent

58
Q

What state is the person undergoing fMRI in?

A

Unconscious state

Neuro (25 decks)

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