Blood Supply and CSF [1] Flashcards
Trace the path a corpuscle might take from the internal carotid artery to somatosensory cortex to the jugular vein. Does it matter whether it is the “foot” or “hand” region of somatosensory cortex?
Foot Region:
Internal carotid → ANTERIOR cerebral artery → somatosensory cortex → superior sagittal sinus → confluence of the sinuses → transverse sinus → sigmoid sinus → internal jugular vein
Hand Region:
Internal carotid → MIDDLE cerebral artery → somatosensory cortex → superior sagittal sinus → confluence of the sinuses → transverse sinus → sigmoid sinus → internal jugular vein
YES it matters- The foot regions is located close to the sagittal midline, the area served by the anterior cerebral artery. The hand region is more lateral and is served by the middle cerebral artery
How might blood from the left vertebral artery reach the frontal lobe of the right side in case of occlusion of an internal carotid artery?
Left vertebral artery → basilar artery → right posterior cerebral artery → right posterior communicating artery → right internal carotid → right middle cerebral OR right anterior cerebral artery (depending on where in the frontal lobe you’re headed).
Draw and label the components of the circle of Willis
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Describe the difference in physical relationships between the CNS, layers of the meninges and the bone, comparing the situation in the cranium to that for the spinal column
The CNS is separated from the bone encasements (cranium and spinal column) by 3 tissue layers which collectively form the meninges. From inside out, these are: pia, arachnoid and dura.
The pia is a single layer of cells closely covering the outside of the CNS. The arachnoid forms a loose, spongy layer between the pia and dura. The dura is a leathery layer which is closely applied to the cranium, but which hangs loosely within the spinal column.
The arachnoid space is filled with the same specialized fluid (CSF) that fills the ventricles.
Trace the path of CSF from its place of formation in the lateral ventricles to its site of resorbtion in the arachnoid granulations
Lateral ventricle → foramen of Monro (interventricular foramen) → third ventricle → aqueduct of Sylvius (cerebral aqueduct) → fourth ventricle → subarachnoid space via 3 cisterns (two lateral, one caudal) → flows around subarachnoid space → arachnoid granulations
Be able to identify on MRI images, CAT scans and sections through the brain: lateral ventricle, third ventricle, fourth ventricle, interventricular foramen, cerebral aqueduct, cisterna magna, interpeduncular cistern
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Describe the relationship between ependymal cells and capillaries in the choroid plexus and how CSF is formed by this structure
Ependymal cells: line the inside of the ventricles to form a leaky barrier most of the time
Choroid plexus: specialized areas of ependymal cells, mainly in the lateral ventricles, that produce CSF
Normally in the brain you have leaky ependymal cells and tight endothelial cells. In contrast, in the choroid plexus you have tight ependymal cells and leaky endothelial cells. This means that in the choroid plexus, the ependymal cells have free access to blood contents, but also have to take over active transport functions normally performed by the endothelial cells. The fluid source for CSF seems to be fluid from the plasma that leaks through the lose endothelial junctions.
Approximately, what is the volume and rate of production of CSF?
About 500mL of CSF is made every day, though the total volume of CSF at any particular time is only about 125mL.
100mL of this 125mL is outside of the ventricles in the subarachnoid space. Thus, you fill and empty the entire CSF system four times per day
Describe what happens to the composition of CSF as the ionic composition of plasma changes.
Fluctuations in plasma ion concentrations generally produce little to no effect on the ion concentrations in the CSF because of its careful regulation.
If you were to start altering the ionic composition of the CSF, you would be at risk of randomly hyperpolarizing or depolarizing CNS neurons, leading to epileptic-like activity in the brain. n.
Distinguish between communicating and non-communicating hydrocephalus
Non-communicating hydrocephalus: the flow of CSF is interrupted by obstruction of an interventricular foramen or of the cerebral aqueduct.
Communicating hydrocephalus: the CSF gets to the subarachnoid space but isn’t reabsorbed properly.
