Cerebral Vasculature and Brain Homeostasis

Question 1

Intraventricular foramen

Answer 1

Connects lateral ventricles to 3rd ventricles

Question 2

Cerebral aquaduct

Answer 2

Connects 3rd and 4th ventricles

Question 3

Median aperture

Answer 3

Connects 4th ventricle to cisterna magna

Question 4

Lateral apertures

Answer 4

Connects 4th ventricle to arachnoid space

Question 5

Hydrostatic pressure

Answer 5

Equal to blood pressure
Pushes the fluid out of the capillary
Tissue hydrostatic pressure pushes fluid in to capillary

Question 6

Oncotic pressure

Answer 6

Osmotic pressure
Inside capillary- pulls fluid in
Surrounding capillary- pulls fluid out

Question 7

CSF production in relation to intracranial pressure

Answer 7

CSF production is constant over a wide range of intracranial pressure (even if pressure is getting high, CSF will continue to be made)

Question 8

Bicarbonate HCO3 concentration in plasma vs CSF

Answer 8

Equal

Question 9

Arachnoid villi

Answer 9

Absorb CSF from arachnoid space into dural venous sinuses

Proportional to intracranial pressure- higher pressure causes more to be absorbed

Question 10

Blood brain barrier

Answer 10

Formed by tight junctions b/w endothelial cells and the foot processes of astrocytes

Question 11

Glucose transporters in BBB

Answer 11

Glut1 transporters
Not insulin-dependent
Larger transporter on capillaries, smaller one on astroglia
Glut3 transporter for neurons

Question 12

What can cross BBB via passive diffusion

Answer 12

H20
CO2
O2
Free steroid hormones (not protein bound)

Question 13

Na/K/2Cl transporter

Answer 13

Moves all these ions from CSF to blood

Related to K+ levels, when K+ levels are high, it starts transporting out of CSF

Question 14

P-glycoprotein

Answer 14

Takes drugs from CSF and kicks them back to the blood

Question 15

BBB exceptions

Answer 15

Areas of brain that require exposure to blood borne substances- tight junctions are removed
Posterior pituitary
Area postrema in medulla (vomiting)
Organum vasculosum
Subfornical organ
Latter two are involved in control of body water

Question 16

Circle of willis disruption

Answer 16

There is not much mixing of blood from different inputs to the circle of willis, so if one is disrupted, that area of the brain will be damaged

Question 17

Cerebral circulation innervation

Answer 17

Parasympathetic
Ach
Vasoactive intestinal polypeptide
Causes vasodilation
Sensory innervation of distal blood vessels by:
Substance P, Neurokinin A, CGRP (all dilation)- activation leaves to headaches (can be caused by decrease in CSF volume)
Decreased CSF leaves to torqueing of blood vessels, then these NTs are released