Cerebral Circulation Flashcards
What is the total cerebral blood flow?
750 mL/min
Approximately what percent of body weight is the brain?
2%
What percent of resting CO will the brain get?
13-14%
How long does it take for lack of cerebral blood flow to induce fainting?
5 seconds
Cerebral blood flow under what value (mL/min) will cause irreversible brain damage?
10 mL/min
At what CBF value does cerebral impairment begin? Flat line EEG?
20-25 mL/min; 15-20 mL/min
What is the flow to the grey matter in mL/min/100g? White matter?
60-80; 20
The brain consumes what percentage of resting oxygen?
20%
What is the%O2 extraction in the brain?
30% extraction
What percent of body’s glucose is used by the brain at rest?
50%
How does the brain autoregulate cerebral blood flow?
Changes in resistance (vasodilation/ vasoconstriction)
What is the effect of arterial PCO2 on cerebral blood flow?
Small increases in PCO2 result in large increases in CBF
What is the effect of increasing ventilation on cerebral arteriole radius?
Vasocontriction
Neurometabolism is especially effective at regulating what kind of blood flow?
Regional blood flow
What metabolites stimulate vasoconstriction?
H+, K+, adenosine, CO2,
What is flow-metabolism coupling?
Increased blood flow to active tissue
What types of cells are included in the neurovascular unit?
Endothelial, pericytes, astrocytes
What is the ratio of pericytes to endothelial cells?
1:03
How does glutamate mediate vasodilation?
Glutamate binds to NMDA receptors on neurons, allowing for calcium influx which activates nitric oxide synthase, producing NO and causing vasodilation
True or False: SNS stimulation is not necessary to maintain proper cerebral blood flow?
FALSE
What is the strongest extrinsic activator of the cardiovascular system?
Cerebral ischemia
What is Cushing’s Reflex?
A physiological nervous system response to an increase in intra-cranial pressure
What is Cushing’s Triad?
Hypertension, Brandycardia, slow-irregular breathing
What structures create the brain-blood barrier?
Cerebral endothelial cells in the capillaries have continuous tight junctions with end/foot of an astrocyte surrounding the capillary
What is the clinical use of mannitol? What is the basis of its action?
Can be used as an oncotic agent to draw water out of the brain; carbohydrate that cannot cross BBB- oncotic agent
True or False: The blood brain barrier is has an equal permeability throughout the brain?
FALSE
What compounds can the brain use for energy?
Glucose and ketone bodies
What is the most important glucose carrier in the brain?
GLUT1
What is the aproximate volume of CSF?
100-160 mL
What produces cerebrospinal fluid?
Choroid plexus
How much CSF is made daily?
400-600 mL
What are the functions of CSF?
Buoyancy, Shock absorption, intracerebral transport
Where does the CSF circulate throughout the brain?
Subarachnoid space
Where is CSF reabsorbed into the venous system?
Arachnoid villi (granulations) into the superior sagittal sinus
What is the relationship between cerebrospinal fluid and extracellular fluid?
They are in communication/equilibrium with one another
