Karius CSF flow

Question 1

CSF ml at any given moment around brain/SC

Answer 1

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

Question 2

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

2 lateral to what?

Answer 2

4th ventricle to cisterna magna

4th ventricle to arachnoid space

Question 3

50-70& of CSF is made by what?

Answer 3

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

Question 4

Formation of CSF a 2-step process:

Answer 4

1. Passive filtration of serum

2. Modification of serum

Question 5

Passive filtration of serum depends on 2 pressures:

Answer 5

Hydrostatic pressure and oncotic pressure

Question 6

hydrostatic pressure

Answer 6

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

Question 7

Oncotic pressure

Answer 7

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

Question 8

The modification of serum (step 2) is controlled by

Answer 8

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

Question 9

Relationship between CSF production and pressure?

Answer 9

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

Question 10

CSF = plasma

Answer 10

Sodium, Na and bicarb HCO3

Question 11

CSF > Plasma

Answer 11

Mg, Cl, CO2

Question 12

CSF < Plasma

Answer 12

K, Ca, Protein, Glucose

Question 13

Absorption of CSF is proportional to what?

Answer 13

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

Question 14

The main role of CSf is to what?

Answer 14

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

Question 15

Capillaries in brain have what 2 components that limit exchange?

Answer 15

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

Question 16

What substances can cross BBB via passive diffusion?

Answer 16

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

Question 17

BBB allows glucose entry via what?

Answer 17

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

glut3: allows glucose into neurons

Question 18

Na/K/2Cl transporter

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

BBB functions mainly in

Answer 21

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

Question 22

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

Answer 22

the capillaries do not have tight junctions between endothelial cells

Question 23

the 4 circumventricular organs are:

Answer 23

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

Question 24

Brain blood requirements per minute are:

Answer 24

750 ml/min, 14% of blood pumped

Question 25

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

Answer 25

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

Question 26

Sympathetic innervation of cerebral blood flow:

Answer 26

leads to constriction when systemic CO/BP increases

Question 27

Sympathetic innervation of cerebral blood flow NTs and receptors?

Answer 27

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

Question 28

Parasympathetic innervation of cerebral blood flow:

Answer 28

cause vasodilation, physiologic relevance uncertain

Question 29

Parasympathetic innervation of cerebral blood flow NTs and Rec

Answer 29

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

Question 30

Sensory innervation of distal brain BVs release:

Answer 30

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

Question 31

Local Control of cerebral blood flow by:

Answer 31

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

Question 32

Cerebral Blood flow and MAP

Answer 32

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

Question 33

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

Answer 33

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