A&P Test 2 Flashcards
CNS is surrounded by 3 layers of connective tissue called the
Pia- thin layer
arachnoid mater-thin layer
dura mater- thick and leathery
subarachnoid hemorrhage happen in the
subarachnoid space
What is the dividing point between the cns and pns?
spinal nerves
the Pia, arachnoid, and dura mater cover the nerve until the point of
where the rootlets join together and form that spinal nerve
Spinal meninges are the
pia mater
arachnoid mater
dural mater
The meninges are covering up the
central nervous system
What is immediately outside of the dura layer?
epidural space
epidural space is filled with
fat and venous blood vessels
Because the epidural space is fatty, many of our lipophilic drugs are going to be
sucked into the adipose tissue making onset longer and wearing off longer after the drugs are stopped
What is a spinal?
when drugs are injected into the subarachnoid space. Onset is faster, but more dangerous
Where is the safest place to do a spinal? why?
In the lower back below L1
The spinal cord splits up into the cauda equina
What is the tip of the spinal cord called?
Conus medullaris
Where is the conus medullaris found?
L1
The enlargement at the top of the spine is called the
cervical enlargement
Where is the cervical enlargement found?
C3-C6
The enlargement at the bottom of the spine is called the
lumbar enlargement
Where is the lumbar enlargement found?
T11-L1
The cervical enlargement nerves exit the spinal cord and form the
brachial plexus
The lumbar enlargement nerves exit the spinal cord and form the
lumbar plexus and sciatic nerve
The dura mater are continuous with the nerves all the way down until the
bottom of the sacrum
What is the cuada equina made of?
posterior and anterior spinal roots
What is the extension of the pia matter that comes off the conus medullaris and ends in the dural sac, that anchors the cord and all of those structures to the spine?
the Filum terminale
What is the dural sac filled with?
CSF
What is the dural sac?
a continuation of the dura and arachnoid maters
What is another name for the lumbar sac?
Lumbar cycstern
the dural sac extends to the level of
S2
What is the upper portion of the ligament called at the end of the spinal cord?
Filum Terminale Internum
from end of cord to end of sac
What is the ligament that starts at s2 and anchors the bottom portion of the dural sac in place?
Filum Terminale Externum
Where does the conus medullaris end in a newborn?
L3
Why does the conus medullaris shift upwards as we mature?
Because the bones grow faster than the cord lengthens.
What is the downside to having the lumbar cystern at the bottom of the spine?
The CSF in the Lumbar cystern is “stale”
Where is a good place to sample CSF?
in the lower back; in the subarachnoid layer
Which vertebral space do we use to pull CSF or infuse meds into the spine?
L3-L4 interspace
L4-L5 interspace
Take CSF results from the lumbar cystern with a grain of salt because
the CSF is “stale” here
Besides the L3-L4 and L4-L5 interspaces to inject meds, what is another access point in the spine?
Sacral hiatus
What is one benefit to using the epidural space instead of giving a spinal?
You don’t puncture the CSF holding space so CSF doesn’t leak out when you pull the needle out
What is a place to inject meds in the sacral spine?
posterior sacral foramina
What angle should you shift the needle while giving an epidural or spinal?
15 degree angle
What is a arachnoid trabeculae?
pillar like structures the help hold open the arachnoid space and makes sure there is enough room for our blood vessels and CSF to provide a cushion for the brain
our bones are not solid structures and are innervated by
arteries and veins
When we crack the skull, we create an
epidural hematoma
majority of the epidural hematomas are
arterial
Subdural hemorrhages are mostly
venous, because the dura layer is basically continuous with some of the venous sinuses
subarachnoid hemorrhages are typically
arterial
CSF pH is_____
why?
7.31
there is less HCO3-
CO2 is constantly made through cellular metabolism making it more acidic
Na+ levels in the CSF are
140mOsm, about the same as plasma
Cl- levels in the CSF are
close to the Na+ levels, about 140mOsm which is more than the plasma
K+ in the CSF is about ____ than in the plasma
40% less
Mg+ in CSF are _____ than plasma
higher
What electrolyte concentrations are going to limit our neurological activity?
Na+
Cl-
K+
Mg+
CSF glucose is about
60mg/dL
Plasma glucose is about
90mg/dL
What color should CSF be?
clear
What is the volume of CSF?
150mL
How fast is CSF made in a day?
500mL/day
What separates the CSF from the cardiovascular system?
Ependymal cells
Ependymal cells are leaky to which electrolytes?
Na+
Cl-
Water
How does an ependymal cell get electrolytes into the CSF?
Through a Na+ ATP pump
Sodium leaves the cell
Cl- follows Na+
Water follows both Cl- and Na+
How can anesthetics increase or decrease CSF production?
by slowing down or speeding up the Na+ ATP pump
Which cell manages K+ levels in the CSF?
astrocytes
what is a group of ependymal cells called?
choroid plexus. found in a bunch of the parts of the brain’s CSF circulatory system.
What are the containers of the CSF circulatory system called?
Ventricles
The third ventricle is located where the
diencephalon and hypothalamus is
The fourth ventricle is located where?
middle of the brainstem next to the cerebellum
what are the two ventricles called at the top of the brain?
the left and right lateral ventricles
where is CSF made?
in choroid plexuses in the ventrucles
Name the CSF flow through the brain
- Left and right lateral ventricles
- interventricular foramen (foramen of monroe)
- 3rd ventricle
- cerebral aqueduct (aqueduct of Sylvius)
- 4th ventricle
* central canal
* lateral apertures (foramen of Luschka)
* median aperature (foramen of Magendi)
- cerebellomedullary cistern (cisterna magna)
The foramen of monroe is also called
the interventricular foramen
The aqueduct of Sylvius is also called
the cerebral aqueduct
The foramen of Magendi is also called
the median aperture
If we occlude one of the exit points in the CFS pathway, we would expect
the ventricles to swell and cause a problem
Where is the most common block in the CSF pathway?
in the cerebral aqueduct (aqueduct of sylvius)
What is non-communicating hydrocephalus?
A block in the pathway of the production and emptying system
What is communicating hydrocephalus?
ventricular system is intact but for whatever reason the CSF isn’t being absorbed like it should be so we have pressure building up surrounding the brain
Hydrocephalus gives us
high ICP and problems with brain profusion
normally CSF is absorbed at the same clip that it is
being made
Where are CSF reabsorbed in the CSF circulation?
at arachnoid granulations
What are arachnoid granulations?
infoldings found at the longitudinal fissure. They are the CSF blow-off valves that open for a ICP > 10mmHg to mediate CSF reabsorption
What is a normal ICP?
10mmHg
The majority of the CSF is reabsorbed at the arachnoid granulations but some is reabsorbed in the
spinal cord
If we have a stroke and clots form over the arachnoid granulation, you would expect to see
communicating hydrocephalus and increased pressures throughout the system
What is the cerebellum?
part of the brain that is responsible for coordinating complex tasks
What is the compartment located at the base of the skull that can be accessed to pull fresh CSF?
Cerebellomedullary cistern (cisterna magna)
What is another name for the Cisterna magna?
cerebellomedullary cistern
What feeds the Cerebellomedullary cistern (cisterna magna) with CSF?
the median aperture
Sinus in the cardiovascular system is a
big vein
What is the sinus that runs midline in the sagittal plane of the skull is called the
superior sagittal sinus
Parallel and Below the Sagittal sinus is the
Inferior sagittal sinus
What is the fan of connective tissue that separates the left brain from the right cerebral hemispheres?
Falx Cerebri
The Falx cerebri continues down to the back of the brain and provides a floor for the occipital lobe to sit on called the
Tentorium cerebelli
Below the Tentorium cerebelli is the
cerebellum
The small stretch of vessel that connects the superior and inferior sinus is called the
straight sinus
From the straight sinus, blood follows a lateral path to the left and right of the skull to provide an exit point for the blood returning from the superior and inferior sagittal sinuses called the
transverse sinus
The sinus confluence is where
the superior sagittal, inferior sagittal and straight sinus all connect
The blood comes from the transverse sinuses and makes a hairpin turn at the
sigmoid sinus
The venous collection pool that is located in the front middle part of the brain that feeds the face and front of the brain is called the
cavernous sinus
Where is all of the cranial blood emptied into?
The internal jugular
The exertnal jugular takes care of the more
superficial structures on the side of the head
We have vertebral arteries that supplies blood to the
back of the brain
we have two internal carotid arteries that supplies blood to the
internal structures of the brain
The external carotid arteries are in charge of supplying blood to the more
superficial parts of the brain
Arterial blood flow is about ______mL/min
and _____ of our CO
750
15%
Cardiac output is
5L/min
the brain makes up what percent of the body weight?
2-3%
lopsided blood flow
How much blood is supplied per minute per grams of tissue?
50mL/min/100g of tissue
how much of blood flow to the brain goes to grey matter?
80%
The main metabolic requirement of the CSN is to get blood to the
grey matter
