Lecture 10/11 - CNS Circulatory Systems Meninges Flashcards
Exam 2
What is the downside of having the grey matter superficial in the brain?
Prone to concussion
Arterial vs venous bleed
Arterial bleeds get worse quicker, venous bleed slower to progress
The pia mater sits on top of _____ in the brain
Neural and glial cells, outside border of the brain
The space between the pia mater and the arachnoid mater is the ______. What is in this space?
Subarachnoid space - blood vessels and CSF
A subarachnoid hemorrhage is ______ in nature
arterial
aka arterial aneurysms
The ______ are the pillars that create space between the arachnoid and pia layers
Arachnoid trabeculaes - create space for CSF and blood vessels
A subdural hemorrhage is ______ in nature
venous - slower to develop, headache a couple days after trauma
A _______ is when the arterial blood vessels rupture with a skull fracture
Epidural hematoma
Which layer perfuses the skull?
The dura layer - cranial sinuses
What is the total volume of CSF?
150 mL
What is the rate at which the CSF is produced?
500 mL/day - replaced 3x a day on average
What cells are responsible for maintaining the electrolyte levels of the CSF?
Astrocytes
pH of CSF vs plasma
CSF pH more acidic
- blood 7.4
- brain 7.31
Why is the CSF more acidic than the blood?
- Lower bicarb level in CSF - more acidic
- Brain has its own buffer system with bicarb to remove CO2 that is produced through metabolism
Na levels of CSF vs plasma
140 - same
Cl levels of CSF vs plasma
Higher in CSF than plasma
Same as Na - 140
K levels of CSF vs plasma
40% less than normal plasma values - 2.4
The ______ doesn’t get refreshed with CSF as much as areas higher up
Lumbar cistern
Mg levels of CSF vs plasma
Higher in CSF
The changes in electrolyte concentrations in CSF helps keep the _____ on the NS
brakes
How do different electrolyte values in the CSF help keep the brakes on neurological systems?
Raising Cl - makes more (-) - hyperpolarized, GABA receptors
Lower K - hyperpolarized cell
Higher Mg - lower overactivity
Glucose levels of CSF vs plasma
Lower in CSF → 60 mg/dL
Plasma 90 mg/dL
Why is glucose lower in the CSF than in the plasma?
Glucose is transported into CSF via GLUT1 transporters
Follows concentration gradient (facilitated diffusion) so need CSF < plasma
- CSF uses glucose
- Neurons can’t store glucose as glycogen - need transport in
What are the units used for glucose concentration?
mg/dL
CSF samples should be ______ in color
clear - no RBCs or proteins
What are the units used for electrolyte concentration?
mEq/L
______ cells produce CSF and separate CSF from blood
Ependymal
Differentiate between ependymal cells, astrocytes, and microglia
All are types of glial cells
- Ependymal cells - produce CSF, line ventricles and central canal; have cilia
- Astrocytes - provide nutrients to neurons, maintain their extracellular environment, and provide structural support
- Microglia - main form of active immune defense in the CNS
Differentiate between ganglia and nuclei
Ganglia are clusters of nerve cell bodies in the PNS
Nuclei are clusters of nerve cell bodies in the CNS
Differentiate between neurons and glial cells
Neurons are the “communication” cells
Glial cells are the “support” cells of the nervous system
If you want to increase the rate of CSF production, you can give an anesthetic that
Increases the rate of sodium pumping into CSF from ependymal cells
If you want to decrease the rate of CSF production, you can give an anesthetic that
Decreases the rate of sodium pumping into CSF from ependymal cells
CSF production relies on
The active sodium pump moving sodium into the CSF from the ependymal cells
- Dictates rate of Cl and H2O movement into CSF
What regulates the potassium levels in the CSF?
Astrocytes - potassium accumulation
Where does CSF glucose come from?
Anywhere with a BBB, doesn’t need specialized cells
What tissue is CSF produced in?
Choriod Plexus - consists of ependymal cells
Where is the choroid plexus found?
4 ventricles - shown in red
The 3rd ventricle is in the location of the _______
diencephalon, right around where the hypothalamus is
Where is the 4th ventricle located?
In the middle of the brain stem, anterior to the cerebellum
What are the names of ventricles 1 and 2? Where are they located?
Lateral ventricles - in the cerebral hemispheres L/R
What is the name of the pathway that the CSF takes from the lateral ventricles to empty into 3rd ventricle
Interventricular Foramen aka Foramen of Monroe
What is the name of the pathway that the CSF takes to get from 3rd → 4th ventricle
Cerebral Aquaduct aka aquaduct of Sylvius
What is the name of the pathway that the CSF takes to get out of the 4th ventricle?
There are 2:
Lateral Apertures - aka foramen of Luschka; left and right exit of 4th ventricle
Median Aperture - aka foramen of Magendie; exit midline and out the back of 4th ventricle; allows CSF to circulate around cerebellum
What pathway allows CSF to leave the 4th ventricle and circulate the cerebellum?
Median Aperture - aka foramen of Magendie
Posterior, midline of 4th ventricle
What pathway allows CSF to leave the 4th ventricle and travel back to the circulatory system?
Lateral Apertures - aka foramen of Luschka; left and right exit of 4th ventricle
Where is the majority of the CSF reabsorbed back into the CV system? Where are they located?
Arachnoid granulations - infoldings above the longitudinal fissure
How do arachnoid granulations decide how much CSF volume to empty into the CV system?
Pressure blow-off valves - normal pressure is 10mmHg
Which pathway is the most common cause of blockage of CSF drainage?
cerebral aquaduct (tumor)
What is the term for extra fluid in the circulatory system of the brain? What does this result in?
Hydrocephalus - increased ICP, putting pressure around the surrounding tissues and neurons
What are the types of hydrocephalus?
Non-communicating - occluding of CSF pathway
Communicating - pathways are intact, but CSF not being absorbed like it normally is
Where does ICP increase based on the type of hydrocephalus?
Non-communicating - increased ICP above blockage, results in swelling of the ventricles
Communicating - generalized increase in ICP
How fast is CSF reabsorbed into the CV system?
Usually, CSF is reabsorbed into the CV system at the same rate that it is being produced
- depends on the pressure
What kind of hydrocephalus occurs as a result of a stroke caused by a clot in the arachnoid granulations?
Communicating
What kind of hydrocephalus results in ventricular enlargement?
Non-communicating