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NEER E2 > Karius CSF flow > Flashcards

Karius CSF flow Flashcards

1
Q

CSF ml at any given moment around brain/SC

A

150 ml; not recirculated so make ~550 ml/day

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2
Q

The median aperture of 4th ventricle allows flow into what?

2 lateral to what?

A

4th ventricle to cisterna magna

4th ventricle to arachnoid space

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3
Q

50-70& of CSF is made by what?

A

Choroid plexus, the remaining is made by tissue that line the ventricles and BVs

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4
Q

Formation of CSF a 2-step process:

A
  1. Passive filtration of serum

2. Modification of serum

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5
Q

Passive filtration of serum depends on 2 pressures:

A

Hydrostatic pressure and oncotic pressure

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6
Q

hydrostatic pressure

A
  1. The pressure inside the capillary and 2.around the surrounding tissues. Inside capillary is basically blood pressure. Tissue pressure usually ‘small’ so 1 wins
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7
Q

Oncotic pressure

A

The pressure that objects pulls towards themselves. Inside capillary, proteins etc pulls pressure into capillary, same with tissues. In choroid plexus this is equal and opposite so cancels out

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8
Q

The modification of serum (step 2) is controlled by

A

channels on the epithelial cells for bicarb, Cl and K. Aquaporin 1 allows H2O to cross

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9
Q

Relationship between CSF production and pressure?

A

Production of CSF is constant over a wide range of pressures. Even if ICP is high CSF production will continue

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10
Q

CSF = plasma

A

Sodium, Na and bicarb HCO3

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11
Q

CSF > Plasma

A

Mg, Cl, CO2

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12
Q

CSF < Plasma

A

K, Ca, Protein, Glucose

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13
Q

Absorption of CSF is proportional to what?

A

ICP; below 68 mmCSF no absorb.
normal pressure = 112 mmCSF
inc. pressure will damage neurons

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14
Q

The main role of CSf is to what?

A

protect the brain. brain weight in air is 1400g in CSF is 50g

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15
Q

Capillaries in brain have what 2 components that limit exchange?

A
  1. Tight junctions between endothelial cells
  2. Glial endfeet in close contact with BVs. aka extra lipid bilayers
    * this results in us needing transporters for things we want exchanged
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16
Q

What substances can cross BBB via passive diffusion?

A

H2O (via AQP4)
CO2
O2
free steroid hormones (note that most steroid hormones are protein bound)

17
Q

BBB allows glucose entry via what?

A

glut1 transporter: not insulin dependent. 55k on caps and 45k on astroglia

glut3: allows glucose into neurons

18
Q

Na/K/2Cl transporter

A

moves all those ions from CSF to blood. Seems to be related to [K] in CSF -if K is high starts shoving others out

19
Q

Expression of the Na/K/Cl transporter controlled by what?

A

release of endothelin 1 & 3 from endothelial cells of the BVs

20
Q

Many drugs able to cross the BBB are moved back to blood via what?

A

P-glycoprotein; binds to a wide variety of substances (this isnt typical of most transporters)

21
Q

BBB functions mainly in

A

protecting chemical comp. of CSF, esp K, maintenance of Vm, protection from toxins

22
Q

There are 4 areas (circumventricular organs) where we want open exchange and to handicap the BBB, we do this by what?

A

the capillaries do not have tight junctions between endothelial cells

23
Q

the 4 circumventricular organs are:

A
  1. POST. PITUITARY -releases hormone into blood
  2. Area Postrema- vomiting
    3,4. Organum vasculosum of the lamina terminalis (OCLT), and subfornical organ- both are involved in control of body water/thirst/blood volume
24
Q

Brain blood requirements per minute are:

A

750 ml/min, 14% of blood pumped

25
Q

The circle of willis has little blood mixing despite appearance, what is impact of this?

A

disruption of one of the inputs produces localized, discrete areas of ischemia

26
Q

Sympathetic innervation of cerebral blood flow:

A

leads to constriction when systemic CO/BP increases

27
Q

Sympathetic innervation of cerebral blood flow NTs and receptors?

A

NTs: Norepi & Neuropeptide Y(NPY)
Rec: alpha-adrenergics

28
Q

Parasympathetic innervation of cerebral blood flow:

A

cause vasodilation, physiologic relevance uncertain

29
Q

Parasympathetic innervation of cerebral blood flow NTs and Rec

A

NTs: Ach, VIP, PHM27 (derived from pre-pro VIP

30
Q

Sensory innervation of distal brain BVs release:

A

Substance P, Neurokinin A, CGRP-all dilators, sense brain moving more bc weighs more

lead to pain

31
Q

Local Control of cerebral blood flow by:

A

oxygen, consumption of oxygen will dictate where blood goes in brain

32
Q

Cerebral Blood flow and MAP

A

Cerebral blood flow is held constant over a wide range of Mean arterial pressure. It is ‘autoregulated’ 60-140mmhg constant

33
Q

In the face of high blood pressure sympathetics in the bran will do what?

A

vasoconstrict, although this inc. systemic vascular resistance it protects capillaries in the brain and therefore the BBB

NEER E2 (4 decks)

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