General Neurophysiology Flashcards
Blood Pressure=?
(HR x Stroke volume) x Total peripheral resistance (TPR)
Where do the afferents from the baroreceptors synapse?
Nucleus Tractus Solitarius (NTS)
The secondary afferents from the NTS do what to the depressor region (parasympathetics) and what to the pressor region (sympathetics)?
Stimulate depressor and inhibit presser
Blood flow to the brain is under ______ control
Local
Why is baroreceptor/central control unable to override local control mechanisms in the brain?
Largely due to reduced/absent sympathetic innervation of the vasculature
Can CO2 and hydrogen cross the blood brain barrier?
CO2 CAN
H+ CANNOT
What is ventriculomegaly and what can cause it?
An enlargement of the ventricles as a result of hydrocephalus but there is also a congenital form which is not related to increased intracranial pressure
What things have about the same concentration in CSF and plasma?
- Na
- Cl
- HCO3
What things are greater in concentration in the CSF than in plasma?
- Mg
- PCO2
- creatine
What things are lowing in concentration in the CSF than in plasma?
- K+
- Glucose
- Ca
- Protein
- Inorganic phosphate
- Urea
- Uric acid
- Cholesterol
pH of CSF?
7.33 (7.4 in plasma)
What foreman does CSF travel through after it leaves the ventricle?
- Magendie
- Luschka
What is the mechanism by which the mesothelial cells of the arachnoid villi take up CSF?
Bulk pressure driven flow and also Pinocytosis
Below what pressure does absorption of CSF stop?
68 mm CSF
What is hydrocephalus?
accumulation of excess CSF and results from a mismatch of production and reabsorption
What are the general causes of hydrocephalus?
- Decreased absorptive capacity of the arachnoid villi (external or communicating)
- Blockage of either foreman or somewhere else in the ventricular system (Internal or non communicating)
What is the transporter that allows glucose to enter the CSF from the blood?
GLUT1 (not insulin dependent)
What is the Na/K/2Cl transporter stimulated by?
ET-1 and 3
Areas of the brain that do NOT have a tight blood brain barrier?
- Posterior pituitary (hormone release into blood
- Area Postrema (chemotactic trigger zone that initiated vomiting from blood-borne chemicals
- OVLT (osmoreceptor for ADH) thirst
- Subfornical organ (Angiotensin acts here to initiate thirst)
Sympathetic innervation of cerebral vasculature
- Post ganglionics from superior cervical ganglion
- Norepinephrine and NPY
- ALPHA- adrenergic receptors for vasoconstriction
- Large arteries
Why does a lumbar puncture or decreased CSF cause a headache?
Distal arteries are innervated by nociceptors activated by torsion and reduced intracranial pressure reduced buoyancy which makes the brain heavier and normal motion can cause torsion
At any given moment how much CSF is in the central nervous system?
150 ml
Which form of GLUT1 is on capillaries?
55K
which form of GLUT1 is on astroglia?
45k
Do the GLUT1 transporters need insulin?
NOOOOOOOO!
When a drug crosses the blood brain barrier, what pumps it back to the blood?
P-glycoprotein
Parasympathetics to cerebral vasculature?
- Large vessels
- Ach
- VIP and PHM-27
- vasodilation
What are the substances that cause dilation of smaller vessels in response to torsion and nociception?
- Substance P
- Neurokinin A
- CGRP
