| Question | Answer |
| What accounts for 90% of the cells in the CNS? what are the 3 main types? | GLIAL CELLS.
1.Astrocytes (protoplasmic and fibrous).
2.Oligodendrocytes.
3.Microglial cells.
**all 3 aid in development and maintenance of neurons & Synapses. |
| 3 main functions of Astrocytes (50% of cells in the CNS) | 1.Metabolic compartmentation.
2.Synaptogenesis.
3.Tissue Repair (gliosis).
**Form the BBB and traffic nutrients and waste in and out of neuronal somas (compartmentalize & protect brain). |
| What is Gliosis? | Proliferation of astrocytes which forms glial scars.
**Can be hamrful. |
| Is the neuronal cell membrane exposed to the extracellular? | NO, it is MOSTLY covered by end feet of astrocytes, the rest are locations of Axosomatic synapses. |
| When might you see a fibrous gliosis? | After a stroke |
| Are Oligodendrocytes limited to supporting only ONE axon like Schwann cells are? | NO, they can wrap/myelinate and support multiple axons at a time. |
| Describe the myelin sheath that the Oligodendrocytes wrap around axons | Flat (until axon is rolled up in it), protein and lipid rich.
**Therefore viral infections can trigger an immune response which could then target the myelin (MS in CNS, Guillian Barret in PNS) |
| Corpus Callosum | Heavily myelinated bridge b/w right and left hemispheres of the brain (will appear very white due all myelination).
**Will see plaques there with MS due to overactive microglial cells. |
| What are Astrocytes and Oligodendrocytes derived from? | Ectoderm. |
| What are Microglial cells derived from? | Monocytes that have migrated out of the BL into the brain. |
| What will cause a proliferation of Microglial cells? what is their function? | Damage to the brain, or to the BBB (allows more macrophages to migrate out of the BL).
**They Phagocytize the damaged neurons (serve as the immune system of the brian). |
| What CNS cells are responsible for producing Cytokines? name the 4 it produces | MICROGLIAL CELLS:
1.Interleukin-1.
2.Interleukin-6.
3.Tumor necrosis factor.
4.Transforming growth factor. |
| 3 types of cells lining the brain | 1.Ependymal cells (line the ventricles).
2.Choroid plexus (proliferating ependymal cells that produce CSF by acting like a glomerulus found in EACH ventricle).
3.Pial cells (flattened cells lining entire brain minus ventricles). |
| Since the brain is protected by BBB and linings, how do hormones and ions reach the BL from the Hypothalamus? | Ependymal cells. |
| What connects the 2 lateral ventricles? | Interventricular foramen. |
| Where does the 3rd ventricle lie? what connects it to the 4th ventricle? | MIDLINE.
**The cerebral aquaduct connects it to the 4th. |
| Where does the CSF go from the 4th ventricle? | It drains into the subarachnoid space via 3 foramina (2 lateral, 1 medial). |
| Is there a choroid plexus in every ventricle? | YES. The CSF it prodcues only circulates b/w the ventricles and subarachnoid space. |
| Is CSF production under neurogenic control? if so, what Inc or Dec production? | YES.
**SNS adrenergic system DEC production.
**PNS cholinergic system INC production (by 2X). |
| How much CSF is produced per day and what drives its movement? | 500-600mL per day (40% is extruded off ventricular wall).
**Movement results from a hydrostatic gradient between ventricles and venous channels. Ventricular pressure can be 180 mm of water while that of the superior sagittal sinus is 90 mm of water |
| 2 ways CSF drains from the subarachnoid space | 1.Subarachnoid granules of superior sagittal sinus.
2.Spinal granulations of spinal nerves. |
| 2 main functions of CSF | 1.Waste removal.
2.Helps brain combat gravity by providing a floating material. |
| Hydrocephalus | Imbalance b/w CSF prduction and drainage which leads to a build up of CSF from:
1.Overproduction.
2.Occlusion/blockage.
**Very Destructive. |
| What occurs in hydrocephalus as a result of the build up of CSF? | Brain becomes erroded. |
| What does hydrocephalus sometimes follow? (due to the increased dead brain tissue draining into the CSF and clogging the drainage pathways) | STROKE (will develope rapidly afterwards if this occurs). |
