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Year 2 Collin > Neuro 5 - Regulation of Blood flow > Flashcards

Neuro 5 - Regulation of Blood flow Flashcards

1
Q

Approximately how much of the CO does the brain take? (only 2% of body mass)

A

15%

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2
Q

What is syncope?

A

(=fainting)

Due to reduced blood supply to the brain

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3
Q

What can cause syncope?

A
  1. Low BP
  2. Postural changes
  3. Vaso-vagal attack
  4. Sudden pain
  5. Emotional shock, etc
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4
Q

What is the principal energy source of the brain?

A

Glucose

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5
Q

What are the normal fasting glucose levels?

A

4-6 mM

Below 2mM can cause unconsciousness, coma and death

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6
Q

Total cerebral blood flow is auto regulated between which mean arterial blood pressures?

A

60 - 160 mmHg

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7
Q

How is blood flow maintained over the wide range of MABPs?

A

Stretch-sensitive cerebral vascular SM contracts at high BP and dilates at low BP

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8
Q

What happens above the autoregulated pressure range of 60-160 mmHg

A

Increased blood flow leads to swelling of brain tissue - ICP increases which is dangerous

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9
Q

How can local regulation of cerebral blood flow be controlled?

A
  1. Neural control

2. Chemical control

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10
Q

Describe the pattern of vascularisation of CNS tissues

A

Surface Pial vessels —> branches penetrate into brain parenchyma —> form capillaries, which form veins which drain into surface pial veins

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11
Q

What are the 4 neural factors that regulate cerebral blood flow

A
  1. SNS nerve stimulation - causes main cerebral arteries to vasoconstriction - probably when there is high MABP
  2. PNS stimulation (facial nerve) - produces slight vasodilation
  3. Central cortical neurones - release many vasoconstrictor neurotransmitters (e.g. catecholamines or adrenaline)
  4. Dopaminergic neurones produce vasoconstriction - effect can be localised according to increased brain activity
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12
Q

How do dopaminergic neurones exert a local effect?

A

They innervate the penetrating arterioles and pericytes around capillaries

They may participate in diverting cerebral blood to regions of high activity

Dopamine may cause pericytic contraction vie aminergic and serotoninergic receptors

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13
Q

What are pericytes?

A

Cells that wrap around capillaries, and have a variety of functions

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14
Q

What chemical factors can regulate local cerebral blood flow?

A
  1. CO2
  2. pH
  3. NO
  4. K+
  5. Adenosine
  6. Anoxia

(ALL VASODILATOR)

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15
Q

What produces CSF?

A

Regions of choroid plexus in cerebral ventricles

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16
Q

What cells line the ventricles, aqueducts and canals of the brain?

A

Ependymal cells (they are epithelial-like glial cells that are often ciliated)

17
Q

What are the choroid plexus?

A

Ependymal lining that has been modified to form branched villus structures

18
Q

Describe the capillary and ependymal cell structure of choroid plexus cells

A

Capillaries are quite leaky

But the local ependymal cells have got extensive tight junctions

19
Q

CSF is secreted by choroid plexus into ventricles. via what does CSF enter the 3rd ventricle?

A

Interventricular foramina

20
Q

How does CSF enter the subarachnoid space?

A

Via medial and lateral apertures

21
Q

What are the functions of CSF?

A

Protection, nutrition of neurones and transport of molecules

22
Q

Roughly what is the volume of CSF?

A

80-150ml

23
Q

CSF has little protein in it, how can this be used clinically?

A

If there is protein found in CSF, could indicate a problem

24
Q

At what level is the blood brain barrier present?

A

At the level of the CNS capillaries

25
Q

What are the 3 types of capillary?

A
  1. Continuous
  2. Fenestrated
  3. Sinusoid
26
Q

BBB capillaries have extensive tight junctions, more as you go down from pial arterioles to capillary

A

T

27
Q

Name 2 differences between BBB capillaries and peripheral capillaries

A

Peripheral vessels = spare pericyte coverage, BBB vessels = dense pericyte coverage

BBB capillaries have “end-feet” astrocyte coverage - important for maintaining BBB properties

28
Q

How are pericytes important for BBB vessels?

A

Pericytes help maintain capillary integrity and function

29
Q

Hydrophilic solutes cannot cross the BBB. What does this mean?

A

Membrane transporters are present on BBB to control substance access into and out of CNS (influx / efflux transporters)

30
Q

Are the meninges’ vessels BBB?

A

No

31
Q

How does access to / removal of lipophilic substances occur in the CNS?

A

Diffusion down concentration gradients

32
Q

Name 4 hydrophilic substances that access the brain and how

A
  1. Water, via AQP1 and AQP4 channels
  2. Glucose via GLUT1 transporter proteins
  3. AA, via 3 different transporters
  4. Electrolytes via specific transporter systems
33
Q

What are CVOs?

A

Circumventricular organs. Regions of the brain (near ventricles) whose capillaries lack BBB.

34
Q

Describe the capillary structure of CVOs

A

Fenestrated capillaries, ventricular ependymal lining is much tighter than in other areas

35
Q

What are CVOs used for?

A

Secreting into the circulation of to sample the plasma

36
Q

Give 3 examples of CVOs

A
  1. PPG
  2. Median eminence
  3. Area postrema - samples plasma for toxins and induces vomiting

Year 2 Collin (114 decks)

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