Chapter 61

Question 1

What metabolic factors are related to cerebral blood flow?

Answer 1

• [CO2]
• [H+]
• [O2]
• astrocyte releases

Question 2

When [CO2] and [H+] are increased in the CNS tissues, what happens to cerebral blood flow?

Answer 2

-it increases to carry away the waste and bring fresh nutrient

Question 3

How does O2 affect cerebral blood flow?

Answer 3

-if pO2 drops below 30mmHg then dilation of cerebral vessesls is stimulated.

Increases flow

Question 4

What happen when sympathetic activity causes a rise in arterial BP?

Answer 4

-the larger and medium cerebral vessels constrict to lower the BP in the distal capillaries and prevent hemorrhage.

Question 5

What happens when sympathetic innervation to the cerebral vessels is lesioned?

Answer 5

-little cerebral flow modulation exists

Question 6

How do astrocytes help to regulate cerebral blood flow?

Answer 6

• vasodilation is mediated by several vasoactive metabolites released by astrocytes
• stimulation of excitatory glutaminergic neurons leads to increases in intracellular Ca+ in the astrocyte foot causing vasodilation

Question 7

Does cerebral blood flow change much in individuals with BP ranging from 60-140 (or even 180)mmHg?

Answer 7

No, autoregulation of larger and mesium vessels prevents this. See earlier picture

Question 8

What is a stroke? (yes, I’m serious)

Answer 8

-occurs when cerebral blood vessels are blocked and cause a disturbance in brain function

Question 9

How can HTN cause a stroke?

Answer 9

• Blood vessel rupture and hemorrhage
• compresses brain tissue and compromises function

Question 10

What is the most common stroke type?

Answer 10

-Blockage of the MCA

Question 11

What are the signs and symptoms in a left MCA stroke?

Answer 11

• Motor and sensory deficits on the right side
• Los of wernike’s area (speech comprehension) and loss of Broca’s area (speech production: motor component)

Question 12

What are the signs and symptoms of a PCA stroke?

Answer 12

-Loss of upper and contralaeral visual field (ipsilaeral retina)

Question 13

What is the main dependant factor of fluid secretion by the choriod plexus?

Answer 13

-Na+ movement attracting Cl- and therefore causeing osmosis of water along with it

Question 14

What other movements of substances in the CSF are less important?

Answer 14

• Movement of glucose into the CSF
• Movement of K+ and HCO3- out

Question 15

How do arachnoidal villi allow for the movement of particles and CSF into venous circulation?

Answer 15

-Cells have vesicular passageways directly through the large cell bodies that allow free movement of:

–> CSF

–>protein

–>red and white blood cells

out and into the venous blood

Question 16

How do arachnoid villi regualte CSF volume and therefore pressure?

Answer 16

• Production of CSF is almost always contrant, therefore modulation has to come from the reabsorbtion
• vesicles in the arachnoid villi function like valves, they allows movement into the venous system as long as the venous system pressure is about 1.5mmHg lower than the CSF pressure.
• As CSF pressure increases, the “valves” open more widely and allow for higher filtration rates.

Question 17

Can damage to the arachnoid villi like large particulate matter, fibrosis or excess blood cells, compromise CSF drainage?

Answer 17

-Absotootly

Question 18

What disease states can cause high CSF pressure and blockages?

Answer 18

• brain tumors compromising reabsorbtion
• Hemorrhage or infection clogging the arachnoid villi
• Abnormally formed arachnoid villi or not enough functional ones (infant hydrocephalus)

Question 19

How does increased ICP cause papillodema?

Answer 19

-the dura of the brain extens along with the optic nerve to connect with the sclera.

High ICP pushes excess fluid into this nerve sheath, then along the spaces between the optic nerve to the interor of the eyeball. High pressure then decreases venous drainage and therefore causes increased IOP

Question 20

What is the functional permiability of the BBB?

Question 21

What is the functional unit of the BBB?

Answer 21

Tight Junctions

Question 22

Is it possible to obtain theraputic concentrations of protein antibodies in the CSF or other proetinous based drugs?

Answer 22

• No not really.
• Pretty much no.

I guess it depends……If they ask on the test though, I would say no.

God I am sick of these cards.

Question 23

What are the major causes of brain edema?

Answer 23

• greatly increased capillary pressure
• damage to the capillary wall that makes it leaky to fluid

Question 24

Even though it is not explicitly in the objectives, why does brain edema tend to feedback positively?

Answer 24

• compression of vasculature leads to ischema which then leads to further dilation and leakyness of vesels
• decreased blood flow leads to low [O2] which again causes increased blood flow and more leakage

Question 25

Does the brain use a lot of our glucose?

Answer 25

-Hells yes. Accounts for about 15% of total metabolism.

Question 26

Does the transport of glucose into the neurons through the cell membrane dependant on glucose in the brain? Why is this important?

Answer 26

No

Question 27

Do the neurons in the CNS have a high glycogen stores in the case of hypoglycemia?

Answer 27

No- bad for diabetics who take too much of their insuline