General Neurophys - Karius 3/24 Flashcards
What are the 2 stages in the creation of CSF?
- Passive filtration of serum
2. Ionic modification
What ions are modified during creation of CSF?
What else?
HCO3, Cl, K
Aquaporins
What ends up in equal [ ] in both the plasma and CSF?
Na
Cl
HCO3
What ions are greater in CSF than plasma
Mg
CO2
What is lower in CSF compared to plasma?
K
Ca
protein
Glucose
What absorbs CSF?
How is it moving?
Arachnoid villi
Bulk flow into venous sinus and pinocytosis
Relationship between absorption of CSF and intracranial pressure?
Proportional
At pressures below what, will no CSF be absorbed?
What is normal pressure?
68mm CSF
112mm CSF
What limits exchanges in the BB barrier?
Tight junctions bw endothelial cells
Glial end feet in contact w/blood vessel
What can cross the BB barrier via passive diffusion?
H2O, CO2, O2, free steroid hormones
What transporter does the BB barrier use for glucose?
Relationship with insulin?
What forms?
GLUT1
Insulin independent
55K on capillaries
45K on astroglia
What is the fx of the Na/K/2Cl transporter?
It’s expression is tied to what?
And this is related to what?
Moves these ions from CSF to blood
Endothelin 1 and 3
Signal from astrocytes
May be related to [K]csf
What moves drugs that have cross the BB barrier from CSF back into the blood?
P-glycoprotein and MDR-1
Fxs of BB barrier?
Protect CSF from blood borne agents
Maintain electrolyte compoisition (K+, Vm)
Protection from toxins
Prevent escape of nts
Areas that are susceptible to substances that cross the BB barrier are missing what?
What is the purpose?
What is the consequence?
Tight junctions bw endothelial cells
Allow certain parts of the brain access to plasma [ ]
Areas exposed to toxins that the rest of the brain is protected from
What are the areas that are not protected from the BB barrier?
Also give what they do
Post pituitary - release hormones
Area Postrema - vomiting
OVLT + subfornical organ - control body water/thirst/blood V (Angiotensin)
How much of the CO does the brain receive?
14% or 750mL/min required
The vasculature of the brain gets Symp innervation from what nt’s?
What are the receptors?
Leads to what?
NE and NPY
Alpha-adrenergic
Constriction when CO/BP INC
Vasculature of the brain receives PS innervation from what?
What parts of the brain?
Result?
Ach, VIP, PHM-27
Larger blood vessels
Vasodilation
What nt’s cause sensory innervation dilation of blood vessels?
Substance P
Neurokinin A
CGRP
PAC dat d
Sensory fibers render the blood vessels of the brain extremely sensitive to what?
Leads to what?
Torsion/manipulation
Pain
Reduced CSF makes the brain heavier leading to torsion of the brain and thus pain. Activation of those afferents will cause what?
Vasodilation and INC blood flow
What kind of control is cerebral blood flow under?
Local
Oxygen consumption dictates where in brain blood goes
What makes CSF?
Choroid plexus
Tissue lining the ventricles and blood vessels
As intracranial pressure increases, what happens to venous outflow?
Arterial flow?
Obstructed
reduced arterial flow
What controls cerebral blood flow?
Held constant over what range of what?
Autoregulation
60-140 mean arterial BP
If mean arterial BP goes too high what can extend the autoregulation of the brain?
Sympathetic stimulation to Vasoconstrict
What may increases the intracranial pressure?
Hydrocephalus
Edema
Bleeding within the skull
