General Neurophysiology Flashcards
______ tissue makes Cerebrospinal Fluid?
Choroid Plexus (makes about 50-70% 0f the CSF) remaining CSF is made by the tissue that lines the ventricles and blood vessels
What are the two stages of making CSF?
Step 1: passive filtration of serum
Step 2: HCO3, CL, and K concentrations controlled by channels on epithelial cells, aquaporins also exits
T/F Production of CSF is constant over a wide range of intracranial pressures?
True
_____, ______, and ______ are equal or nearly equal in the CSF and plasma?
Na+, Cl-, and HCO3
_____ and _____ are in greater concentrations in the CSF than the plasma?
Mg2+ and CO2
_____, ______,_____, and ______ are in lesser concentration in the CSF than the plasma?
K+, Ca2+, protein, and Glucose
T/F CSF is recirculated.
False
make about 550 ml/day
What does CFS flow through?
ventricles, through the different foramen
Absorption of CSF is performed by ______ ____?
arachnoid villi
endothelium of sinus and the membrane on the villu have fuse; bulk flow of CFS into venous sinus is primary, pinocytosis also documented
( w/ aging the fusion of the membrane increases thus the CSF bulk flow decreasing therefore increase CFS
Absorption of CFS is proportional to _____ _______?
intracranial pressure
- at pressure below 68mm CSF, no absorption
- increased pressure causes damage to neurons
What is the role of the CSF?
to protect the brain (weight in air: 1400g; weight in CSF; 50 g; effect of CSF: priceless)
_______ and _______ are the two components in the capillaries that limit exchange
tight junctions b/w endothelial cells and glial endfeet come in close contact with blood vessel
_______, ________, _______, and _________ passively diffuse across the brain barrier.
H20, CO2, O2, free steroid hormone (most are protein bound)
lipid soluble molecule may cross
What is the major energy source for neurons?
glucose (does not cross the blood barrier readily)
How does the glucose get transport into the brain?
GLUT 1 transporter (not insulin-dependent) Two forms (45 and 55 K): 55K on capillaries, 45K on astroglia
What transporter moves all those ions from CSF to blood?
Na/K/2Cl transport, expression tied to endothelin 1 and 3
ET production tied to a signal from the ______?
astrocytes
may be related to [K+] CSF
___________ transports move drugs back across the BBB?
p-glycoproteins (type of MDR-1: protects the compositions of the CSF)
What is the function of the BBB?
protect the chemical composition of the CSF from blood-borne agents
maintain electrolyte composition (K= and membrane potentials)
protection from toxins
prevent escape of neurotransmitters
_______ are places where the brain is exposed to the blood?
Circumventricular junctions (capillary dont have tight junctions; allowing for paracellular transport)
What are the 4 circumventricular junctions?
The posterior pituitary ( neurohpophysis, release hormones into blood) Area Postrema ( aka chemoattrackant tigger center) causing vomiting reflex to blood-borne pathogens Organum vasculosum of the lamina terminalis (OVLT) Subfornical organ (both control of body water/thirst/blood volume)
Describe the sympathetic innervation of the Cerebral Circulation.
neurotransmitters: norepi, and NPY
receptors: alpha-adrenergics (vasoconstriction)
fires only when systemic BP is toooo high to protect the brains
Describe the parasympathetic innervation of the cerebral Circulation.
Larger blood vessels
Ach and vasoactive intestinal polypeptide (VIP) and PHM-27
cause vasodilation
Describe the sensory innervation of the cerebral circulation
sensory innervation to the distal blood vessels
Neurotransmitters: Substance P, nerokinin A, and CGRP (all cause dilation)
