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Neuroscience & Mental Health Y2 > Regulation of Blood Flow / Blood Brain Barrier > Flashcards

Regulation of Blood Flow / Blood Brain Barrier Flashcards

1
Q

unconsciousness will result If CBF is interrupted for as little as …

A

4 seconds

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2
Q

What is SYNCOPE

A

Fainting

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3
Q

Causes of syncope? (5 -> resulting in?)

A

including low BP, postural changes, vaso-vagal attack, sudden pain, emotional shock etc. resulting in temporary interruption/reduction of blood flow to the brain

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4
Q

a VAST SURPLUS of glucose to the brain via the blood is important because….

A

the brain cannot store, synthesize or utilise any other source of energy (ketones to an extent during starvation)

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5
Q

HYPOGLYCAEMIA can occur as a result of?

A
  • Poorly managed diabetes
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6
Q

Symptoms of hypoglycaemia? (3)

A
  • Disorientation, slurred speech, impaired motor function
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7
Q

What is the level of blood glucose for unconsciousness

A

below 2mM

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8
Q

2 mechanistic targets of regulation of blood flow to brain?

A
  1. Mechanisms affecting total cerebral blood flow

2. Mechanisms which relate activity to the requirement in specific brain regions by altered localised blood flow

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9
Q

How is TOTAL CEREBRAL BLOOD FLOW regulated? what is the BP kept between?

A

Autoregulated, Kept between MABP of 60-160mmHg

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10
Q

What changes take place in high and low pressure blood flow to the brain to VSMC?

A
  • Stretch-sensitive cerebral vascular smooth muscle contracts at high BP and relaxes at lower BP
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11
Q

LOCAL CEREBRAL BLOOD FLOW 2 ways of control?

A
  • Neural control

- Chemical control

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12
Q

4 neural factors that affect cerebral blood flow resulting in vasoconstriction/dilation?

A
  1. Sympathetic nerve stimulation- vasoconstriction
  2. Parasympathetic nerve stimulation- vasodilation
  3. Central cortical neurones- releasing vasoconstrictor neurotransmitters e.g. catecholamines
  4. Dopaminergic neurones- vasoconstriction
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13
Q

How do DOPAMINERGIC NEURONES control blood flow? What do they innervate? What do they do? What effect does dopamine have?

A
  • Innervate penetrating arterioles and pericytes around capillaries (pericytes are cells that wrap around capillaries and can be contractile)
  • May participate in diversion of cerebral blood flow to areas of high activity
  • Dopamine may cause contraction of pericytes via aminergic and serotoninergic receptors
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14
Q

PATTERN OF VASCULARISATION of the brain? where do the arteries come from? where do the veins go? (think layers)

A
  • Arteries on the pial surface of the meninges produce branches that penetrate down into the parenchyma to form capillaries
  • These drain into venules which drain into pial veins
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15
Q

Chemical factors that influence local cerebral blood flow and their effect and do they cross the BBB or are they generated in the brain?? (7)

A
  1. CO2 (indirect- it actually affects pH via carbonic anhydrase and produces H+ ions)- vasodilator (CROSSES)
  2. pH (H+, lactic acid etc.)- vasodilator (DOESNT CROSS)
  3. Nitric oxide- vasodilator
  4. K+- vasodilator
  5. Adenosine- vasodilator
  6. Anoxia- vasodilator
  7. Other (kinins, prostaglandins, histamine, endothelins)
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16
Q

What does the choroid plexus do

A

Produce CSF

17
Q

What is the choroid plexus

A

Some regions in the ventricles where ependymal cells are modified to form branched villus structures. This is the choroid plexus

18
Q

Describe the formation of CSF

A
  • Capillaries are leaky, but adjacent ependymal cells have tight junctions at the plexus- not at all leaky
  • Choroid plexus ependymal cells secretes CSF into ventricles and it circulates (route of circulation in a previous lecture)
19
Q

Route of circulation of the CSF? (7)

A

o Lateral Ventricles
o 3rd Ventricle (via interventricular foramina)
o Cerebral Aqueduct
o 4th Ventricle
o Subarachnoid Space (via medial and lateral apertures)
 These openings lead to the subarachnoid space so have a continuous connection between ventricles and subarachnoid space.
o The fluid as its being produced will leak back into the venous system e.g. superior sagittal sinus via arachnoid granulations.
o It circulates around.

20
Q

3 functions of the CSF?

A

o Protection (chemical and physical)
o Nutrition of neurones
o Transport of molecules

21
Q

What is molecules are lacking in CSF?

A

protein

22
Q

Levels in CSF compared to blood of:
K
Mg
Ca

A

K - lowered
Mg - higher
Ca - lower

23
Q

• The pH of the CSF is slightly more X

A

ACIDIC

24
Q

• OSMOLARITY OF the CSF IS XX

A

THE SAME

25
Q

BBB - THE CAPILLARIES OF THE CNS PARENCHYMA DERIVED FROM XXX

A

SURFACE PIAL CELLS

26
Q

Where is the BBB found?

A

Capillaries of the CNS

27
Q

4 differences between BBB and normal capillaries?

A

BBB capillaries have little/no transcellular vesicular transport
their inter-endothelial tight junctions are much less leaky
- BBB capillaries have much denser pericyte coverage
- BBB capillaries are covered with “END FEET” from astrocytes (the ends of some of the astrocyte processes)

28
Q

What type of molecules cross the BBB easily

A
  • LIPOPHILIC molecules (O2, CO2, alcohol, anaesthetics?)
29
Q

How do water, glucose, amino acids and electrolytes cross the BBB?

A

WATER AQP1/AQP4 channels
GLUCOSE GLUT1 transporter proteins
AMINO ACIDS 3 different transporters
ELECTROLYTES Specific transporter systems

30
Q

Type of capillary in the circumventricular organs?

A

fenestrated

31
Q

capillaries in the circumventricular organs are generally involved in…

A

secreting into the circulation, or sampling plasma

32
Q
  1. The BBB breaks down in many pathological state such as? (4)
A

Inflammation, infection, trauma, stroke

33
Q

1st gen histamines [can/can’t] cross the BBB

A

can

34
Q

why cant 2nd gen antihistamines cross the BBB, and why is this useful

A

because they are polar, so they don’t cause drowsiness

35
Q

How is issue of dopamine being unable to cross the BBB sorted in Parkinsons

A
  • L-DOPA can cross the BBB via an AA transporter, and is converted to dopamine in the brain
36
Q

What do we administer with LDOPA and why

A

We co-administer L-DOPA with CARBIDOPA, a DOPA decarboxylase inhibitor to prevent peripheral breakdown of dopamine

Neuroscience & Mental Health Y2 (18 decks)

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