3. Cerebral Vasculature and Brain Homeostasis Flashcards
What are the main compositions within the skull?
10% CSF
10% blood/vasculature
80% brain (20% interstitial fluid, 60% intracellular fluid)
CSF is renewed every 6hrs and can be found in ventricles, cisterns and subarachnoid space. What are 4 of its functions?
cushioning
distributing secretory signals
regulating neurogensis
waste clearance
What does CSF do to the weight of the brain?
without CSF, the brain weighs as much as a toaster
with CSF, buoyancy allows the brain to float = gold ball weight
Choroid plexus cells make CSF. What can be found on the ventricular lumen (apical) and then blood side (basolateral)?
Apical: Na/K ATPase and AQP1
Basolateral: NCBE (Na dependent chloride bicarbonate exchanger) and AQP1
What moves water from the blood to the ventricles across the choroid plexus cells?
osmotic gradient
the Na/K ATPase creates an electrochemical gradient for Na resulting in what which creates what? *******important
Net flux of Na, HCO3, and Cl from blood into ventricles creating the osmotic gradient that drives H20 into ventricles via AQP1
What three things are greater in CSF than blood serum?
Cl-
CO2
pH more acidic (7.33)
What 3 main things are greater in serum than CSF?
protein
glucose
pH more basic (7.41)
What two things are equal after equilibration between CSF and blood serum?
Na and osmolarity
Production of CSF is constant over a wide range of intracranial pressures. Absorption of CSF is proportional to what?
intracranial pressure (as ICP inc, so does CSF and vice versa)
The brain receives 15% of cardiac output with blood flow of 750-900mL/min. What are the four main regulations of blood flow to the brain?
CO2 (inc in blood CO2= inc blood flow)**
[Hydrogen Ion] (inc=vasodi=inc blood)
[O2] (dec = inc blood)
Astrocyte Metabolites
Sympathetics leads to vasoconstriction when BP/CO increase to protect brain from surges. What are the NT/ receptors?
A-adrenergic via NE/ neuropeptide Y
Parasympathetics lead to vasodilation when CO/BP decreases to inc. blood to the brain. Via which NT and receptor? (4)
cholinergic via ACh, VIP, NO
Sensory innervation via NT SP and CGRP, which makes cerebral circulation sensitive to pain under what circumstances?
torsion/manipulation decreased CSF (increases brain weight)
What do the following lead to… hydrocephalus, edema, infection, intracranial bleeding and tumor?
increased ICP