General Neurophysiology

Question 1

What transporters are present on the apical and basolateral membranes of the choroid plexus cell and function in the production of CSF?

Answer 1

Basolateral: NCBE (Na/HCO3 exchanger), aquaporin 1

Apical: Na/K-ATPase, aquaporin 1

Question 2

T/F: the blood and CSF isosmotic

Answer 2

True

Question 3

H2O, Na, Cl, and HCO3 are found in higher concentrations in CSF, while ____ ion is found in higher concentrations in the blood

Answer 3

K+

Question 4

An osmotic gradient moves water from the blood to the ventricles across the choroid plexus. What creates the gradient?

Answer 4

Na/K-ATPase creates an electrochemical gradient for Na (increasing its intracellular concentration)

Final result is net flux of Na, HCO3, and Cl from blood across the epithelium and into the ventricles

Question 5

Where are protein, glucose, and pH greater — in serum or CSF?

Answer 5

Serum

Question 6

Production of CSF is constant over a wide range of intracranial pressures. CSF is typically absorbed by ____ ____ which occurs mostly by bulk flow. This absorption is proportional to intracranial pressure, so when intracranial pressure decreases, what happens to absorption?

Answer 6

Arachnoid villi

When ICP decreases, no absorption occurs

Question 7

The brain is 2% of body weight but receives ____% of cardiac output

Answer 7

15

Question 8

Regulators of blood flow to the brain

Answer 8

CO2 regulation

H+ concentratoin

Oxygen concentration

Astrocyte metabolites

Question 9

What effect does increasing CO2 in the blood have on cerebral blood flow?

Answer 9

Increases it

Question 10

Effect of sympathetics on cerebral circulation (and the neurotransmitters involved)

Answer 10

Leads to vasoconstriction when systemic CO or BP increases (protective of brain vasculature)

NTs = NE, NPY

[receptors are alpha-adrenergic]

Question 11

Effect of parasympathetics on cerebral circulation (and the neurotransmitters involved)

Answer 11

Leads to vasodilation when systemic CO or BP decreases (to maximize blood flow to brain)

NTs = ACh, VIP, CGRP, SP

Question 12

How do changes in cerebral circulation cause pain?

Answer 12

Cerebral circulation is innervated — sensory innervation monitors sensation of distal blood vessels using NTs SP, NKA, and CGRP

This renders blood vessels sensitive to torsion/manipulation, leading to pain! Likely to occur in cases of decreased CSF volume which renders the brain heavier

Question 13

Effect of reciprocal activation of sensory afferents on cerebral circulation and CSF volume

Answer 13

Reciprocal activation of sensory afferents activates vasodilation and increases blood flow, perhaps to increase CSF volume

Question 14

Causes of ICP include hydrocephalus, edema, infection, intracranial bleeding, and tumor blockage. What effect does increased intracranial pressure have on cerebral blood flow?

Answer 14

Increased ICP —> obstruction of venous outflow —> reduced arterial flow

Question 15

Sympathetics vasoconstrict vasculature in the face of high BP.

Vasoconstriction by sympathetics ______ systemic vascular resistance but protects the BBB and capillaries

Answer 15

Increases

Question 16

Autoregulation of cerebral blood flow is mediated by _____ stimulation

Answer 16

Sympathetic

Question 17

In the event of reduced brain perfusion, _____ centers are activated which _______ systemic blood pressure and drives blood to the brain

Answer 17

Vasomotor; increases

Question 18

Extrinsic regulators of cerebral blood flow include systemic BP, blood viscosity, and carotid/vertebral vessel lumen occlusions.

Things that affect blood viscosity, like anemia vs. polycythemia would hve what effect on cerebral blood flow?

Answer 18

Anemia (low erythrocyte count, low viscosity) —> increased CBF

Polycythemia (high viscosity) —> decreased CBF

Question 19

Intrinsic factors that affect cerebral blood flow include autoregulation, arterial CO2 and O2, and pH. What effect does CO2 concentration and pH have on cerebral blood flow?

Answer 19

High Pa CO2 (acidosis) —> increased CBF

Low PaCO2 (alkalosis) —> decreased CBF

Question 20

In what parts of the brain would you NOT find the BBB or blood-CSF barrier?

Answer 20

Circumventricular organs (CVOs)

Question 21

Characteristics of BBB in terms of permeability

Answer 21

Highly permeable to water, CO2, O2, and lipid-soluble substances

Slightly permeable to Na, Cl, and K

Nearly impermeable to plasma proteins and non-lipid-soluble organic molecules

Majority of capillaries lack typical slit pores

Question 22

Functions of BBB

Answer 22

Protection

Maintains electrolyte composition of CSF and neural parenchyma

Excludes toxins

Contains NTs

Question 23

Cellular consituents of BBB

Answer 23

Astrocyte endfeet
Pericytes
Endothelial cells

Question 24

What is the major energy source for the brain and how does it cross the BBB?

Answer 24

Glucose; crosses via GLUT1 transport protein (NOT insulin dependent)

Question 25

What transporter transports ions from CSF to the blood across the BBB?

Answer 25

Na-K-2Cl

[expression tied to endothelin 1 and 3; endothelin production tied to astrocyte signal; may be related to [K] in CSF]

Question 26

What role does P-glycoprotein play in transportation across BBB?

Answer 26

Moves drugs that don’t belong that crossed BBB back into the blood

[member of ABC transporter family]

Question 27

The most important glucose transporters in the brain are GLUT1, 3, and 5. Where are these found?

Answer 27

GLUT1 = astrocytes, microvessels, choroid plexus, ependymal cells

GLUT3 = neurons

GLUT5 = microglia

Question 28

What are the 4 circumventricular organs?

Answer 28

Posterior pituitary (secretory; endocrine)

Area postrema (sensory; initiation of vomiting from chemotactic trigger)

Organum vasculosum of lamina terminalis (sensory; regulation of TBW and thirst - target angiotensin II)

Subfornical organ (sensory)

Question 29

What theorized system may assist in macroscopic waste clearance system and is thought to be primarily engaged during sleep?

Answer 29

Glymphatic system