Lec 8 - CNS Flashcards
what types of cells compose 90% of the CNS
glial
what are the two types of glial cells in the CNS
astrocyte - many fxns
microglia - phagocytes
what are the 6 fxns of astrocytes
-develop neural connections
-regulate synaptic activity
-remove NTs from synaptic cleft
-communicate to neurons through chem messengers
-maintain normal electrolyte composition (K+) of ISF in CNS
-protect neurons against toxic substances and oxidative stress
what two things do microglia protect the CNS from and how
-foreign matter through phagocytosis (bact and dead cells)
-oxidative stress by removing ROS
what are the physical supports of the CNS
bones, meninges, CSF
what bones support the CNS
-cranium which encases the brain
-vertebrae through which the spinal cord runs
what are the 3 meninge membranes, where do they lie b/w
-lie b/w bones and tissue of CNS
-dura matter
-arachnoid matter
-pia matter
what are the 4 ventricles of the brain, what fluid are they filled w
-two lateral ventricles called ventricles 1 and 2
-third ventricle
-fourth ventricle
-CSF
what is it called when we collect a sample of the spinal fluid
spinal tap or lumbar puncture
what colour is the CSF, what cells secrete it and where does it circulate and get reabsorbed
-clear
-secreted by ependymal cells of choroid plexus
-circulates to subarachnoid space and ventricles, is reabsorbed by arachnoid villi
what are the fxns of CSF
-phys protection by cushioning brain
-chem protection by maintaining stable ISF enviro
-creates a closely regulated extracellular enviro for the neurons
-choroid plexus selects which substances it transports to ventricles
does plasma or CSF have a higher conc of K, H, Na, does the CSF contain protein or blood cells
-K is lower in CSF
-H is higher is CSF
-Na conc is similar
-v little protein and NO blood cells, presence of these indicates an infection
how many mL of CSF does the choroid plexus produce in a day
400-500mL
what does the choroid plexus consist of and what does it make
-made of pia matter, capillaries, endymal cells
-makes CSF
how many times a day is CSF recycled
3
how much of the blood supply does the CNS use (%)
15
how much oxygen and glucose (%) does the brain consume at rest, what does it rely on for energy
-20 for O and 50 for glucose
-relies on blood flow for energy
why does the brain depend on aerobic glycolysis, and what is it, what does it use during extreme conditions
-requires glucose and oxygen bc no glycogen stores
-ketones
what are capillaries the site of exchange b/w
blood and ISF
what is the blood brain barrier
the way that the anatomy of CNS capillaries limits exchange
what molecules can freely cross capillary walls, how to hydrophobic/philic and cells and proteins move across the endothelial cells
-small molecules (gases, inorg ions, monosachs, aa’s)
-phobic diffuse across membranes of endothelial cells
-philic diffuse through large pores b/w endothelial cells
-proteins and cells are actively transported via transcytosis
does transcytosis occur across capillary endothelial cells in the CNS, what restricts movement of hydrophilic molecules across capillary walls, what is this barrier caused by
-no
-blood brain barrier
-barrier is due to presence of tight jxns b/w capillary endothelial cells which eliminate capillary pores
does the CNS have more grey or white matter, what does grey matter do, why is white matter white
-white
-grey is site of synaptic communication and neural integration
-white due to myelin
what are the 3 types of white matter fibre, what do they do, what what is the corpus callosum
-projection fibres: connect cerebral cortex w lower lvls of brain or spinal cord
-association fibres: connect two areas of cerebral cortex on same side of brain
-commissural fibres: connect same cortical regions on two sides of the brain
-callosum is the primary location of commissural fibres
