Exam 2 - Meninges and Brain Blood Flow Flashcards
What structure is indicated by 2 on the figure below? What two things should be known about this structure?
- Pia Mater
- Pia Mater actually touches neurons and glial cells (essentially inseparable from neurons of cord)
- Pia Mater lies below the large blood vessels.
What structure is indicated by 3 on the figure below? What 2 things should be known about this structure?
The Arachnoid Mater
- Superficial to larger blood vessels with CSF in between arachnoid mater and pia mater
- Connected to dura with very little space in between dura and arachnoid.
What structure is indicated by 5 on the figure below? What two things should be known about this structure?
The Dura Mater of the spinal cord
- The dura mater is the outermost and strongest layer
- The dura mater has no space in between it and the arachnoid mater
What is the potential space between the arachnoid and dura mater called?
Sub-dural space, there is nothing there.
How far out do the spinal meninges go?
To the spinal nerves (end of CNS)
What space is indicated by 2 in the figure below? What inhabits this space?
Subarachnoid space
CSF and blood vessels
What space is indicated by 1 below? What 2 things inhabit this space? What are considerations if this space is accessed?
Epidural space
- Adipose Tissue - Could absorb lipophilic drugs and delay onset and offset
- Epidural Veins - Could bleed or transport drug elsewhere
What space is indicated by 3 in the figure below?
Arachnoid Mater
What space is indicated by 4 in the figure below?
Spinal Dura Mater
What structure is indicated by 1 in the figure below? Why is this a good location for spinals?
The Cauda Equina
There is no cord, faster onset than epidurals, nerves tend to move out of the way if needle is inserted too deep
What is the indicated structure? What does this indicate?
Conus medularis
The end of the spinal cord at L1
What structure is shown by 1 in the C spine below? Why is the spinal cord thicker here? Where do the nerves feed to?
C3 - C6 Cervical Enlargement
Heavy Innervation to upper body
Brachial Plexus
What is the indicated structure and where is it located?
Why is the cord larger here?
What do these nerves feed into?
T11-L1 Lumbosacral enlargement
Lots of innervation to the lower extremities
Sciatic nerve and lumbar plexus
Where does the dura mater end?
It covers all of the nerve roots to the end of the cauda equina and stops at the spinal nerves.
What structure is indicated by 2 in the figure below? What does this connect?
Filum Terminale Externa (extension of pia mater)
Connects end of dural sac to coccyx to anchor it in place
What structure is indicated by 1 in the figure below? What does this connect?
Filum Terminale Interna (extension of pia mater)
The conus medularis to the end of the dural sac
What structure is indicated by 2 in the figure below? What level is this at?
Dural Sac Termination at S2
What structure is indicated by 3 in the figure below? What is contained here?
Dural Sac or Lumbar Cistern
CSF
What is the concept being shown with images 1 and 2?
The difference between the Conus Medularis (CM) in an adult at L1 and the CM in a newborn at L2).
Bones grow faster than the cord lengthens
What needs to be known about the CSF in the dural sac?
It is furthest from the source of CSF (brain) and is not replenished as often because CSF circulation ends at the end of the cord.
What structure is indicated by 3? What is its function?
Arachnoid trabeculae
Creates subarachnoid space for blood vessels and CSF
What is indicated by number 10?
Dura mater
Note its thickness
What is number 11 and 1? Why are these related?
Cranial bone and epidural hematoma
A fracture of the skull, which contains many arterial vessels, can lead to an epidural hematoma which is an areterial bleed
What is 9? What is it made from?
Subdural hematoma
Venous blood from dural sinus tearing
What is number 7? What type of bleed is associated here?
Subarachnoid space
Subarachnoid hemmorage from arterial bleed
What is normal CSF pH? Why?
pH: 7.31
Bicarbonate concentrations are lower than plasma, can’t buffer CO2 as well
What is Na+, Cl-, K+, and Mg++ concentrations in CSF? What do these contribute to?
Na+: 140, equal to plasma
Cl-: 140, equal to Na (higher than plasma)
K+: 40% lower than plasma
Mg++: Higher than plasma
Hyperpolarization of the brain, helping to reduce it’s activity
What is normal CSF glucose? Why?
60 mg/dL
Glucose is brought from plasma by GLUT-1 transporters. It is used readily and not stored in neurons. Also not insulin dependent and glucose just moves down its concentration gradient.
What is normal circulating volume of CSF? How fast is it replaced?
150 mL
500 mL/day (replaced about 3 times per day)
What is the tissue called that is made of ependymal cells? Where are these located?
Choroid plexus
In each of the 4 ventricles
Describe how ependymal cells create CSF? How can anesthetics impair this?
They are leaky to Na, Cl, and H20 on the blood side. On the brain side, Na is pumped across by Na pump. This creates a gradient that allows Cl and H2O to follow (this makes up our CSF).
Anesthetics can slow down or speed up the Na pump and change the rate of CSF production.
What structure is indicated by 2 on the figure below?
Left Lateral Ventricle
What structure is indicated by 2 on the figure below? What structure is this near?
The 3rd ventricle
Diencephalon
What is the circled structure?
The 4th ventricle
What structure is indicated by 1 on the figure below? What should be known about this structure?
The two Foramen of Monroe (interventricular foramen)
This is where CSF flows from the two lateral ventricles into the 3rd ventricle.
What structure is indicated by 7 on the figure below?
Cerebral Aqueduct or Aqueduct of Sylvius (connection point for V3 and V4)
What structure is indicated by 9 on the figure below?
Central Canal
What structure is indicated by 10 on the figure below?
The Left Lateral Apeture of the 4th Ventricle (Foramen of Luschka)
What structure is indicated by 11 on the figure below?
Median Aperture of 4th ventricle (Foramen of Magendie)
Exit point into subarachnoid space for CSF to circulate around the cerebellum
What is the condition of having excess CSF? What are the types? Where is it most common?
Hydrocephalus
Communicating - CSF not being absorbed (blockage of arachnoid granulations). Ventricles not typically enlarged, just high ICP.
Non-communicating - CSF drainage pathway blocked, causing enlarged ventricles: most common in cerebral aqueduct
What structure is indicated by 3 on the figure below? What should be known about this structure?
Arachnoid Granulations - act as pressure blow off valves
If ICP > 10cmH2O then CSF will drain into venous system.
This is where CSF is dumped into venous drainage
What is the function of the cerebellum?
High complex motor movements
What structure is indicated by 10 on the figure below? What structure drains into this one?
The Cerebellomedullary Cistern (cisterna magna)
Median aperture of the 4th ventricle drains here
CSF could technically be accessed here through the foramen magnum by someone brave enough to try.
What structure is indicated by 2 on the figure below? What should be known about this structure?
Superior Sagittal Sinus
This is where Arachnoid Granulations are located, created by being surrounded by dura mater
What structure is indicated by 2 below?
Inferior Sagittal Sinus
What is the connective tissue that seperates the left and right hemispheres?
Falx cerebri
What structure is denoted by 2 on the figure below? What is the purpose of this structure? What lies underneath?
Tentorium Cerebelli
Rigid shelf for occipital lobe
Cerebellum lies underneath
What structure is indicated by 3 below?
Straight Sinus
What structure is indicated by 6 below?
Transverse Sinus
What structure is indicated by 7 below?
Sinus confluence
What structure is indicated by 5 below? Where does this empty blood?
Sigmoid Sinus
Internal jugular vein
What structure is indicated by 3 below? Where does this blood flow come from?
Cavernous Sinus
Venous drainage from eyes and face
What structure is indicated by 3 below? What is interesting to note about where the vertebral artery enters the vertebrae here?
Vertebral Artery
The artery enters at C6 and skips C7
What structure is indicated by 4 below? What important structures would this artery feed?
Internal Carotid Artery
The front and middle of the brain
What structure is indicated by 1 below? What structures does this feed?
External Carotid Artery
Face and facial structures
How much blood does our brain get?
750 mL/min or 15% of cardiac output
Brain is only 2-3% of body mass but recieves a large portion of our CO
How much blood is given per amount of cerebral blood flow? How much is delivered to white and gray matter?
50 mL/min/100 g
80% to grey matter (decisions made)
20% to white matter
Describe the strucutre of the sinuses in the brain? How does this relate to SDH?
They walls are very rigid because they are made up of the dura mater. That is why a subdural results in venous bleed, because the dura tears which allows blood to leak from the sinuses.
What is the main dictator of cerebral blood flow?
The metabolic demand of the brain. An increased demand will result in more flow to the brain. This is meditated by the amount of CO2 released as a byproduct of metabolism.
What is the circle of willis and what is its function?
A circular connection of blood vessels that allows for collateral circulation if one of the feed arteries becomes compromised.
What structure is indicated by 2 below?
Internal Carotid Artery (Left)
What structure is indicated by 11 below? What is the importance of this structure? Where does this structure sit?
- The Right Vertebral Artery
- This structure perfuses the posterior of the brain
- The two vertebral arteries sit on the brainstem
What structure is indicated by 8 below? On which structure does this artery sit? What two arteries converge to form this one?
- Basilar Artery
- Pons
- Left and Right Vertebral Arteries
What structure is indicated by 2 below?
Basilar Artery
What structure is indicated by 15 below?
Precommunicating (P1) of the Posterior Cerebral Artery
What structure is indicated by 16 below?
Postcommunicating (P2) of the Posterior Cerebral Artery
What structure is indicated by 3 below? What large artery precedes this one?
- Middle Cerebral Artery
- Internal Carotid Artery
Middle cerebral arteries is the largest of the circle of willis
What vessels perfuse the pink shaded area?
Anterior cerebral arteries
What vessels perfuse the green shaded areas?
Middle cerebral arteries
What vessels perfuse the purple shaded area?
Posterior cerebral arteries
What structure is indicated by 17 below?
Precommunicating (A1) of the Anterior Cerebral Artery
What structure is indicated by 18 below?
Postcommunicating (A2) of the Anterior Cerebral Artery
What structure is indicated by 1 below? What is its function?
- Anterior Communicating Artery
- Allows for “cross talk” between left and right anterior cerebral arteries
What structures are indicated by 4 below? What do they connect?
- Posterior Communicating Arteries
- Connects the posterior cerebral arteries to middle cerebral arteries
What structure is indicated by 7 below?
Superior Cerebellar Artery
What structure is indicated by 1 below?
Superior Cerebellar Artery
What structure is indicated by 13 below?
AnteroInferior Cerebellar Artery
What structure is indicated by 3 below?
AnteroInferior Cerebellar Artery
What structure is indicated by 12 below?
PosteroInferior Cerebellar Artery
What structure is indicated by 4 below?
PosteroInferior Cerebellar Artery
What cerebral hemorrhage is the hardest to treat?
Subarachnoid hemmorhage. It will leak into the surrounding structures and would cause damage if attempted to be fixed surgically.
How does the brain autoregulate it’s blood flow under normal conditions?
The cerebral arteries will manage flow to the brain based upon the pressure (MAP, CPP). If pressure is high, the arteries will constrict to reduce excess flow to the brain. If the pressure is low, the arteries will dilate to increase flow to the brain.
What is the range of pressures that can be managed by autoregulation? What would happen to flow if we did not have autoregulation?
50 mmHg (LLA) to 150 mmHg (ULA)
Their would be a linear proportional relationship to pressure i.e. flow would be determined by pressure
What changes occur during autoregulation for someone with uncontrolled hypertension? What are the side effects of this?
- Autoregulation will adapt to a new normal by the cerebral arteries contstricing more forcefully than normal to regulate flow.
- This results in arterosclerosis and does not allow them to dilate as well, raising the LLA.
- If this person has a pressure of 50, they will not be able to compensate due to the changes in cerebral vasculature. On the other hand, if they have a hemorrhagic stroke, the vessels cant dilate enough to reduce blood flow, making the bleed worse.
What is a determinant of vascular health?
The ability of the arteries to dilate.
How do anesthetics effect autoregulation?
Most volatile anesthetics effect autoregulation. Lessening the bodies ability to respond to changes in pressure.
What are the 3 main causes of subarachnoid hemorrhage?
EtOH, HTN, and genetics
Where does a minority of CSF flow get reabsorbed? Where does it come from?
Subarachnoid space in the spine
From the foramen of magendie or median aperture of the 4th ventricle
What does the Filum Terminale extend from?
The pia mater