Exam 2: CNS Circulatory System Meninges Flashcards
What is the Tentorium cerebelli?
A shelf/barrier for occipital & cerebellum
What is the average brain mass?
1350g
What is the average blood flow to the brain?
50cc for every 100g of brain mass= ~700cc/min
What separates the Left & Right hemispheres
Falx cerebri
What gives the arachnoid structure?
Arachnoid trabeculae
What cranial meninge is the toughest & holds everything together?
Dura layer
Besides its major function, what does the CSF also serve as in the cranium?
Preserves brain integrity from blows to the head
What produces CSF & at what rate /day?
Ependymal cells produce CSF & produce 450cc/day.
How much CSF is circulating at any given time?
150cc
When is most CSF produced?
During sleep
The lateral ventricles empty into what & by what structure?
Into the 3rd ventricle via the Interventricular foramen
What is another name for the interventricular foramen?
Foramen of Monroe
Which ventricle sits right next to the hypothalamus?
3rd ventricle
How does the 3rd ventricle connect to the 4th ventricle?
Cerebral aqueduct
What structures does the Cerebral aqueduct connect?
3rd & 4th ventricle
What is another name for the Cerebral aqueduct?
Aqueduct of Sylvius
The 4th ventricle sits anterior to what major structure?
The cerebellum
Where does CSF go to when it exits the Median aperture?
Around the cerebellum
What are the CSF exit points from the 4th ventricle called?
Central canal, Median aperture, & 2 Lateral apertures
What structures does the Central canal supply?
The core structures
What is another name for the Median aperture?
Aqueduct of McGendie
Where is CSF turnover the least?
In the lower back & Dural sac around L-1
Where do the 2 lateral apertures drain into?
Front of brainstem & then superior
What are the openings of the Lateral apertures called?
Foramen of Luschka
What is the most common choke/occlusion point in the cranial meninges?
Cerebral aqueduct
What causes non-communicating hydrocephalus & which structures are affected?
Blockage in the cerebral aqueduct. The 3rd and the lateral ventricles would be affected & would become enlarged
What is a normal ICP?
5-10
How is CSF produced?
The Choroid Plexii via Sodium influx to Ependymal cells, Chloride follows which draws water (Ion pumps).
What structures are responsible for CSF production?
Choroid Plexii
What is the CSF blow off valves called & when are they activated?
Arachnoid granulations & at 10cm of water of ICP
Where does most CSF drain into & through what?
Into venous system in the cranium through Arachnoid granulations
What would cause communicating hydrocephalus & why is it called that way?
Blockage of all or most Arachnoid granulations causing an increase in pressure everywhere. Called because the connections between ventricles are not obstructed.
What area does the Median aperture drain into?
Cisterna magna
Besides lumbar puncture what is another access point to retrieve CSF?
Cisterna magna
What is the pH of CSF?
7.31 – 7.32
What are CSF’s Ion concentrations for Na+, Cl-, K+, glucose, pCO2, HCO3? (some have an actual value & some compare to plasma)
Na+= same as plasma
Cl-= +15% than plasma
K+= -40% of plasma
Glucose= 60
pCO2= 47
HCO3= 2 < plasma
What are CSF’s Ion concentrations for Na+, Cl-, K+, glucose, pCO2, HCO3? (some have an actual value & some compare to plasma)
Na+= same as plasma
Cl-= +15% than plasma
K+= -40% of plasma
Glucose= 60
pCO2= 47
HCO3= 2 < plasma
How does the brain get glucose?
Relies on concentration gradient
What are the two things the brain does not store?
Glucose & oxygen
Name the 5 Glial cells?
Ependymal, Schwann, astrocytes, microglia, oligodendrocytes
How does CSF move around the system?
Via passive movement
Cerebral blood flow is determined by what?
Metabolism in the brain
What are the byproducts from brain metabolism?
CO2, Adenosine, O2, H+
What is the Autoregulation range (MAP) for CBF(Cerebral blood flow)?
MAP of 60 to 150
Does cerebral blood flow go up or down when MAP is >150?
Goes up
What mechanism prevents too much cerebral blood flow when MAP increases?
Myogenic constriction, CBF vessels constrict
What happens autoregulation in someone with HTN?
The Lower Limits of Autoregulation & ULA shift. Preventing under & over perfusion.
What is a problem for someone with a long history of HTN having a big drop in MAP?
The cerebral vessels can only dilate so much.
How do you calculate Cerebral Perfusion Pressure (CPP)?
MAP minus ICP
What is the Normal Cardiac output?
5L/min
What average percentage of cardiac output is used for cerebral blood flow?
12-15%
What two categories of work does the CNS fall into & their % of overall use?
Electrophysiology 60% & Homeostasis 40%
What work does the Electrophysiology system do?
Conduct action potentials, resetting cells, maintain RMP, neurotransmitter recycling, Ion transport.
What work does the Homeostasis system do?
Repair worn out proteins, organelles, cell wall rebuild, lipid repair.
Anesthetics will reduce function of the __________ brain system.
Electrophysiology
What 2 anesthetics will not affect the Electrophysiology system?
Nitrous & Ketamine
How does Ketamine work, it is what kind of drug?
It interrupts communication between parts of nervous system, it is a dissociative.
What is the brain’s O2 demand formula?
3.5mL of O2 per 100g of brain mass per minute=
3.5mL x 100g
How much O2 does the whole body use per minute?
250mL/min
How much O2 does the average brain use per minute?
~50mL/min
