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Flashcards in Maintenance of the CNS Environment Deck (40):
0

How much CSF is there at any given moment

150 ml

1

does CSF recirculate?

NO, so we make about 550ml/day

2

Where is most of the CSF made?

The specialized tissue of the choroid plexus (50-70%)

3

Where is the remainder of the CSF made

the tissue that lines the ventricles and blood vessels

4

What is the two step process of CSF formation

1. passive filtration of serum
2. modification of CSF (HCO3-, Cl- and K+ concentrations controlled by channels on epithelial cells, aquaporins also exist)

5

Important note regarding CSF production and ICP

production of CSF is constant over a wide range of ICPs

6

things that ed up in equal concentrations in plasma and CSF (3)

Na
Cl
HCO3

7

things that are present in higher concentration in the CSF than plasma (2)

Mg2+
CO2

8

Things that are present in lower concentrations in CSF than plasma
(4)

K
Ca
protein
glucose

9

CSF flows through the _______. Flow is _______ and CSF must be ________.

ventricular system
one way
reabsorbed at the end

10

Absorption of CSF is through

arachnoid villi

11

arachnoid villi - how is CSF reabsorbed

endothelium of sinus and the membrane on the villi have fused.
bulk flow of CSF into venous sinus is primary
pinocytosis is also documented

12

Absorption of CSF related to ICP

absorption of CSF is proportional to ICP
at pressures below 68mm CSF, no absoption
normal pressure =112 mm CSF
increased pressure causes damage to neurons

13

Role of CSF

to protect the brain
weight in air= 1400g
weight in CSF= 50g

14

BBB - two components that limit exchange in cpillaries in brain

tight junctions between endothelial cells
glial endfeet come in close contact with blood vessel

15

things that can passively diffuse across the BBB

H2O
CO2
O2
FREE steroid hormones (most are bound to protein)

16

major energy source for neurons? Does it cross BBB

glucose, does NOT cross BBB readily

17

How does glucose cross the blood brain barrier

GLUT1 transporter

18

Is the GLUT 1 transporter insulin dependent?

no

19

Two forms of GLUT1 transporters

45K= astroglia
55K= capillaries

20

Importance of NaK2Cl transporter at BBB

moves all those ions from CSF to blood
expression tied to endothelin 1 and 3
ET production tied to a signal from the astrocytes, may be related to [K] in CSF

21

Many drugs do cross the BBB, but are moved back to the blood via?

P-glycoprotein

22

Function of BBB

to protect the chemical composition of the CSF from blood-borne agents, maintain electrolyte composition, protect from toxins, prevent escape of NTs

23

BBB in particular maintains electrolyte composition related to _____. Why?

K+ to keep Vm maintained

24

Circumventricular organs

places in teh brain where we want the brain exposed to the blood.

25

Circumventricular organs are different in that they dont have a BBB. What is different

the capillaries do not have tight junctions between endothelial cells.

26

4 circumventricular organs

area postrema - vomitting
posterior pituitary - releases hormones into the blood
OVLT - control of body water/thirst/ blood volume, angiotensin control
subfornical organ - control of body water/thirst/blood volume, angiotensin control

27

Cerebral circulation receives _______ml (___% of CO)

750
14

28

Circle of Willis is formed by

2 internal carodtids and the basilar artery

29

Does blood from different sources mix in the Circle of willis? What is the impact?

NO
disruption of one of the inputs prduces localized (discrete) areas of ischemia.

30

Sympathetic Innervation of the vasculature
NT
R
effect

NE, NPY
alpha adrenergics
leads to constriction when systemic cardiac output/BP increases

31

Parasympathetic innervation of cerebral circulation
where
NT
effect

larger blood vessels
Ach, VIP, PHM-27 (derived from pre pro VIP)
cause vasodilation

32

Sensory innervation
NT
effect
impact

substance P, neurokinin A, CGRP
DILATION
these sensory fibers render the blood vessls of the brain extremely sensitive to torsion/manipulation - lead to pain

33

Role of Sensory innervation

in reduced CSF volume, the brain is effectively heavier and simple motion can cause bain bc of torsion of the blood vessels
the activation of those afferents will also cause vasodilation and increase blood flow (returns total intracranial volume closer to normal?)

34

Cerebral blood flow is under what kind of control

local control
oxygen consumption dictates where in the brain blood will go

35

What happens to cerebral blood flow as ICP increases

venous outflow is obstructed, leading to reduced arterial flow

36

cerebral bloodflow is strongly autoregulated, meaning

it is held constant over a wide range of systemic (mean arterial) blood pressures

37

In the face of high BP (which could damage the BBB), sympathetics in the brain will _______ the vasculature

vasoconstrict

although this will increase the systemic vascular resistance, it protects the capillaries in the brain from damage - sacrifice the heart for the brain

38

a decrease in brain perfusion will activate the vasomotor centers and _______systemic BP

increase, sometimes drastically. --> the brain will drive the body's bp up in hopes of sending enough blood to the brain to get adequate perfusion

39

what might incrrease the ICP

hydrocephalus of any variety
edema
bleeding within the skull