CSF / meninges

Question 1

Ion transport by choroid plexus epithelial cells

Answer 1

ventricular: Na+/K+ ATPase (Na+ in), Cl- and HCO3- passively diffuse down their gradient into CSF
into epithelial cell from capillary: Na+/H+ exchanger, HCO3-/Cl- antiporter, Cl-/Na+ cotransporter
carbonic anhydrase converts CO2+H2O -> H2CO3 to form HCO3- and H+

Question 2

CSF pressure

Answer 2

at 112 mm CSF, absorption = formation
lower than 68 -> absorption stops (net gain of CSF)
higher than 112 -> more absorbed than formed (net loss of CSF)
CSF formation is constant, absorption variable based on pressure

Question 3

CSF function

Answer 3

make brain lighter
remove brain metabolites from interstitial fluid to veins
regulate brain tissue

Question 4

CSF brain tissue regulation

Answer 4

CSF and ECF are equivalent pH in the brain. Sensors in CSF tell the body what the pH is and then the body can change respiration and cerebral blood flow to achieve homeostasis.

Question 5

Blood-brain barrier

Answer 5

between vessels and interstitial compartment of the brain

capillaries have pericytes, tight junctions, and astroglial cells to prevent some things from coming through

Question 6

blood-brain barrier transport

Answer 6

mainly via transport molecules
GLUT1 - glucose
L system - large neutral amino acids (L-DOPA)
A system - glycine, sort neutral amino acids; powered by Na+/K+ ATPase; manages levels of glycine and glutamate in brain and spinal cord
ASC system - ATPase (alanine, serine, cysteine)
Na+/K+ ATPase

Question 7

blood-brain barrier weaknesses

Answer 7

exist so the brain can measure levels of chemicals / hormones in blood
posterior pituitary (hormone release via fenestrated capillaries)
circumventrular organs

Question 8

Monro-Kellie doctrine

Answer 8

increase in volume of tissues / fluid in skull -> increased intracranial pressure because calvarium fixes the intracranial volume

Question 9

edema

Answer 9

vasogenic - more common

cytotoxic edema

Question 10

vasogenic edema

Answer 10

due to increased permeability of brain capillaries -> increased ECF volume ->lots of swelling around white matter, some around gray matter

Question 11

cytotoxic edema

Answer 11

due to swelling of injured neurons, glia, endothelial cells from hypoxia, asphyxia, or ischemia
Na+/K+ ATPase fails -> Na+ accumulation -> H2O accumulation
could also be due to water intoxication causing systemic hypo-osmolarity

Question 12

hydrocephalus

Answer 12

oversecretion of CSF (due to tumors of choroid plexus - papilomas)
impaired absorption of CSF at arachnoid vili (communicating hydrocephalus)
obstruction of CSF pathways (tumors, congenital malformations, scarring, etc.)
cerebral aqueduct is particularly vulnerable

Question 13

communicating hydrocephalus

Answer 13

enlargement of entire ventricular system without affecting flow after subarachnoid hemorrhage, trauma, or bacterial meningitis
may produce dementia, incontinence, apraxia if there are episodic pressure elevations

Question 14

blood supply of dura

Answer 14

internal carotid, maxillary, ascending pharyngeal, occipital, and vertebral arteries
middle meningeal artery most often injured

Question 15

innervation of dura

Answer 15

above tenroium - CN V

below tentorium - CN X and cranial nerves 1-3

Question 16

headache cause

Answer 16

activation of nociceptors due to changes in meninges or vascular
likely to be abnormal processing as well