L2 Flashcards
what does meninges mean
membrane
what are the 3 layers of the meninges
dura (external), arachnoid (intermediate) and pia mater (internal)
what is in the subarachnoid space
it is a large space filled with CSF
it also contains blood vessels which are poorly protected
where is the sub arachnoid space located
in between the intermediate and internal layer of the miningies
what are the partitions within the skull made of
dura mater
decribe the arachnoid mater
it is a delicit transparent membrane
it does NOT go into the sulci
what connects the arachnoid mater to the pia mater
it is connected to the pia by fine strands of connective tissue called arachnoid trabecula
what does arachnida mean
spider
what is a subarachnoid hemorrhage
when bleeding results in blood being in the CSF
what are arachnoid villi are where are they located
knoblike projections of the arachnoid mater into the venis sines
these are particularly found in the upper parts of the brain at the midline
what are arachnoid granulations
aggregations of arachnoid villi which drain into the venous sinuses
what are cistern
enlarged regions of the subarachnoid space
what is the biggest cistern in the human (there is 2 names for it)
the cerebellomedullary cistern
also called the cisterna magna
where is the cerebellomedullary cistern located
below the cerebellum
where is the interpeduncular cistern
behind the pituitary gland
where is the pontine cistern
in front of the pons
where is the superior cistern
superior to the cerebellum
describe the membrane of the pia mater
it is a delicate membrane which follows cantors of the brain
what surrounds the blood vessels
pia mater
what forms the perivascular space
the pia mater
it does this by sending prolongations into the brain tissue along with blood vessels
what is the pia mater closely associated with
the chloride plexis and the ependyma
what is the chloride plexus
it is where CSF is produced
what are ependyma
these are the cells that line the ventricles
the spinal meninges contain dura. what is different in the spine compeered to the brain
the dura in the spin is made up of only the meningeal layer
it does NOT have a periosteal layer
why does the dura in the spinal cord not have a periosteal layer
the second layer would anchor the spinal cord too much.
you dont want your head to move too much but the spinal cord needs to be able to do a range of movements.
Therefore no having that layer allows for better flexion and extension of the spine
where is the epidural space
between the spinal sural sheath and the vertebral bony wall
what does the epidural space contain
fat tissue and the veins plexus
the fat acts as a cushion for the spinal cord
where is the epidural space largest
below the spinal cord (below L2)
this is where the epidural is injected. when this is done it numbs everything below L2
does the spinal cord have arachnoid and pia mater
yes
where is the lumbar cistern
it is inferior to the spinal cord (below L2)
where is a lumbar puncture performed
at the lumbar cistern (below L2)
why would we do a lumbar puncture
to test to see if there are immune cells in the CSF
if there are it could mean that you have meningitis (inflamation of the meninges)
how does the pia mater act in the spinal cord
it makes up 2 forms of support within the spinal cord
it forms the denticulate ligament which supports the spinal cord within the dural sheath. this provides lateral support
it also makes up the filum terminale which provides vertical support
meningitis is characterised by what
inflamation of the pia-arachnoid
not the dural layer
what is the most common infection of the CNS
meningitis
this is usually caused by a bacterium or a virus
what are common symptoms for meningitis
fever, headache, vomiting and stiff neck (due to inflamation)
more severe symptoms are deffiness, epilepsie and water on the brain
what is the treatment for meningitis
antibiotics
this needs to be administered quickly so that you can prevent the infection from traveling across the pia mater which will cause injury to the neurons of the brain
what are the names of the 4 ventricles
the left and the right lateral ventricles
the 3rd ventricle
the 4th ventricle
what are ventricles
fluid filled spaces in the brain which contain CSF
what connects the lateral verticals to the 3rd ventricle
the inter-ventricular foramen
what connects the 3rd ventricle to the 4th ventricle
the cerebral aqueduct
decribe the different parts of the lateral ventricles
the lateral ventricles consist of a body and 3 horns
the anterior horn is located in the frontal lobe
inferior horn is in the temporal lobe
the posterior horn is located in the occipital lobe
where is the chloride plexus located in the lateral ventricles
in the body and the inferior horn
looks like a backwards C
where is the 3rd ventricle located
between the lateral ventricle and the cerebral aqueduct
where is the chloride plexus located in the 3rd ventricle
in the roof
what structure sits on either side of the 3rd ventricle
the thaliums
where is the 4th ventricle located
it lies between the cerebellum (posteriorly) and the pons and medulla anteriorly
the 4th ventricle has 3 openings which allow CSF to flow out. what are these called
there are 2 lateral apertures (foramina of luschka)
and 1 median aperture (foramen of magendie)
what is the roof of the 4th ventricle formed by
the superior medullary velum
what is the floor of the 4th ventricle formed by
the brainstem
where is the choroid plexus located in the 4th ventricle
the inferior medullary velum
where is CSF located
in the cerebral ventricles, spinal canal and the subarachnoid space
how much CSF does the brain produce/absorb per day
500mL/day
what are the functions of the CSF
buoyancy, protection, chemical stability (homeostasis)
its most important function is buoyancy as it causes the brain to flot therefore decreasing the weight of the brain by 97%
this stops the tissue from compressing down on the tissue underneath
CSF reduced the weight of the brain by how much
97%
what is the blood brain barrier formed by
tight junctions between endothelial cells of the cerebral capillaries
what is the blood brain selective for
nutrients such as glucose, essential amino acids and electrolytes
it keeps out certain chemicals and drugs
what is the role of the blood brain barrier
it acts as a protective mechanism to maintain a stable environment for the brain
what is the blood brain barrier ineffective against
fat soluble molecules (such as alcohol and nicotine), O2, CO2
what is hydrocephalus
water on the brain
hydrocephalus is characterised by an excessive amount of CSF in the ventricular system
what causes this
increased production of fluid
or
disturbance in its circulation (because of a tumor)
or
a problem with absorption into the venus sines
how come babies with hydrocephalus have large heads
In babies the skull is not fused yet which means that the brain can keep getting bigger and bigger
after the skull has fused what does hydrocephalus cause
the pressure causes gradual ventricular dilation which causes compression and thinning of the brain
the ventricles get larger and larger
the brain is 2% of your body weight but receives how much blood
15% which is about 750 mL/min
what % of the bodys oxygen and glucose does the brain consume
20%
if blood flow were to stop to the brain what would happen depending on the time that it happened for
10 sec interruption in flow causes unconsciousness
1-2 min = impaired neural function
4 min + = interruption causes irreversible brain damage
which artery suplys the most blood to the brain
the internal carotid artery
what artery suplys the face and the outside of your skull with blood
the external carotid artery
name the cerebral arteries
basilar artery
vertebral arteries
internal carotid artery
the basilar artery is divided into what
two posterior cerebral arteries
which of the cerebral arteries are found on both sides of the brain
internal carotid artery
anterior cerebral artery (medially)
middle cerebral artery (laterally)
where do the anterior cerebral artery and the middle cerebral artery stem from
internal carotid artery
what is the circle of willis
where the basilar artery connects to the internal carotid artery via posterior communicating arteries
what is the role of the circle of willis
to maintain blood supply to the brain even if one of the main arteries is blocked or narrow
the classic anatomy seen in most diagragm of the circle of willis represents what % of people
33%
the classic anatomy seen in most diagragm of the circle of willis represents what % of people
33%
These is lots of variation and what is happening in your circle of willis has effects on your brain
what does the posterior cerebral artery supply
the medial aspect of the hemisphere (the posterior 1/3 of the brain)
specifically it supplies the occipital lobes, inferior temporal lobe regions, brainstem, the 3rd and lateral ventricles
what does the middle cerebral artery supply
almost all the lateral surface of the cerebral hemispheres
when you put your hand on your head
what does the anterior cerebral artery supply
supplies the medial aspect of the cerebral hemispheres (the anterior 2/3rds) and the basal nuclei
what is a stroke
the neurological dysfunction the results from a reduction of blood supply to the brain
what causes a stroke
a blockage of cerebral artery (or less commonly a vein) leading to cerebral infarction or haemorrhage
this occlusion (blockage) is usually caused by a blood clot, cholesterol deposit or hemorrhagic bleeding from a ruptured vessel
the neurological signs and syndromes of a stroke depend on what
which blood vessels and their branches are involved
occlusion (blockage) of the anterior cerebral artery causes what symptoms
contralateral hemiplegia (one artery) or bilateral paralysis (2 arteries) and impearled sensation
this is greatest in the lower limb
occlusion (blockage) of the middle cerebral artery causes what symptoms
a severe contralateral hemiplegia and impaired sensation mostly in the upper limb and face
you can also get severe aphasia (if the dominant hemisphere is affected) means have trouble speaking
occlusion (blockage) of the posterior cerebral artery causes what symptoms
contralateral homonymous hemianopia (you either see the left of the right visual field)
