| Cytology | ||
|---|---|---|
Cytology | ||
| Cytology | ||
| Question | Answer | Note/Hint |
| What percentage of your energy is used by your brain? | 40% | |
| What type of stain is specific for myelin? | Hiedenheim Stain | |
| Which cell type is larger in general? Neuron or Glial | Neuron | |
| of the 10^13 cells in the brain, what percentage are neurons and what percentage are glial cells? | 1. 10-20% Neurons 2. 90-80% Glial | |
| What percentage of space do neurons and glial space take up respectively? | 50% | |
| What percentage of the brain is extracellular space? In cc's? | 15% or 250cc | |
| As dendrites branch more and more, what happens to their diameter? | It gets smaller. | |
| As an axon extends farther and farther, what happens to its diameter? | It doesn't change. | |
| What manner is information collected by a neuron transmitted? | In a graded fashion | |
| Dendrite information propagation is (Active/Passive)? | Passive | |
| What is concentrated at Nodes of Ranvier? | Sodium Channels | |
| the fastest neuron transmits signals up to what frequency? | 300Hz | |
| Half the energy used by the CNS is used for what? | Maintaining ion concentrations after action potentials (Na/K pump) | |
| Almost all of a neuron's cell membrane is where? | Dendrites | |
| What specific type of cell never uses axons? | Retinal amacrine cells | |
| What type of cell has a fusion of the dendrite and the axon? | Pseudounipolar neuron | |
| How much of the cell body does the nucleus take up? | 1/3 | |
| How many genes make up the CNS set of genes? | 5000 | |
| the outermost nuclear membrane is continuous with what? | the ER | |
| Where does post-transcriptional modification take place in the cell? | the Golgi | |
| What part of a neuron will you find the highest levels of mitochondria? | the nodes of ranvier | |
| the cytoskeleton of a neuron typically contains what three types of fibers? | 1. Neurofilaments 2. Microfilaments 3. Microtubules | |
| What is the substrate for axonal transport? | Microtubules | |
| What does the drug Vincristine do? What is it used for? | It interferes with microtubule formation. This drug is used to fight cancerous tumors. | |
| What is a side-effect of Vincristine? | Tingling in the extremities | |
| How fast is bulk flow of material down an axon? | 1 mm/day | |
| How fast is microtubule flow down an axon? | 40 mm/day | |
| What is delivered to the cell body by way of retrograde transport? What do they let the cell body know? | 1. Neurotrophic factors 2. All is well | |
| the cell nucleus will only replenish what type of NT? | Neuropeptides | |
| What protein is associated with Alzheimers? | Tau | |
| Most excitatory synapses are found where? | Dendritic spines | |
| What do spines contain? | Actin and myosin; contractile | |
| What about your neurons is abnormal in Rett or Down syndrome? | Abnormal dendritic spines | |
| Are chemical synapses unidirectional or bidirectional? | Unidirectional | |
| Which faster, chemical synapse or an electrical synapse? | Electrical synapse | |
| Are electrical synapses unidirectional or bidirectional? | Bidirectional | |
| How large is the gap between two cells (connexons)? | 4nm | |
| What types of materials pass through connexons? | Second messangers, ions and macromolecules | |
| All spaces not occupied by neurons or blood vessels are occupied by what? | Glial cells | |
| Are glial cells polar? Are they signaling cells? | No and No | |
| A lot of healing in the CNS and PNS is due to what? | Scarring of glial cells | |
| the symbiotic relationship between what two cells is very important to the CNS? | Glial cells and Neurons | |
| Glial cells get their energy through what process? | Glycolysis -anaerobic respriration | |
| How many glial cells are their per neuron in a human? | 10 per neuron | |
| What are the two broad categories of glial cells? | Microglial and Macroglial | |
| What are microglial cell's derived from? | Mesoderm; macrophages | |
| What are macroglial cells derived from? | neuroectoderm | |
| What are the two type of astrocytes? | 1. Type I: associated with grey matter 2. Type II: Fibrous astrocytes -associated with white matter | |
| What are the two type myelin-forming cells? | 1. Oligodendrocytes - CNS 2. Schwann Cells -PNS | |
| What is the only glial cell associated with the PNS? | Schwann Cell | |
| where are electrical synapses found? | retina and pacemaking functions (myocardium) | |
| what is a connexon? | a connexon is a gap junction made up of 4 connexins | |
| do glia have connexons/electrical synapses b/t eachother | yes, why else would i ask? | |
| what invades an ischemic area in a stroke? | glia (they dont need O2) | |
| what are the 2 types of glia? | macroglia -everything else microglia -macrophages | |
| embryological origin of microglia? | mesoderm (they are macrophages) | |
| 2 types of astrocytes, structure, location and function | type 1 -short and stubby -in grey matter type 2 - Long processes -in white matter -form end feet on blood vessels | |
| what is principally responsible for enforcing the blood brain barrier? | the astrocytic end feet? | |
| where are radial glial cells cell bodies located? | near the ventricles | |
| why is heroin more potent than morphine? | heroin is more lipophilic and can therefore cross the BBB more easily | |
| what are 3 of the substances that form the BBB? | occludin claudin cadherins | |
| what do astrocytes release that cause the formation of new blood vessels in response to ischemia? | vacular endothelial growth factor (VEGF) | |
| what substance do type 2 astrocytes release that induces the blood vessels to form tight junctions? | angiopoietin-I | |
| what must be given along w/ L-Dopa to allow it to cross the BBB? | MAO inhibitors | |
| what substances are actively transported across the endothelial cell in the brain? | glucose amino acids vitamins | |
| why can glial tumors be given chemotherapeutic agents w/o worrying about the BBB? | they dont have a BBB | |
| why can the loss of one oligodendrocyte in the CNS cause so much damage? | an oligodendrocyte may myelinate 50 different axons. | |
| what molecule makes the initial contact b/t the oligodendrocyte processes and the axon in the CNS? | MCAM | |
| what molecule anchors adjacent layers of myelin in the CNS? | PLP -phospolipid proteins | |
| what molecule anchors adjacent layers of myelin in the PNS? | P0 -protein zero | |
| what molecule serves as a spacer b/t adjacent layers of myelin in the CNS and PNS? | myelin basic protein -MBP | |
| what is the signal conduction velocity in a myelinated axon? | 200 m/s | |
| what determines if an axon will be myelinated in the PNS? | the size of the axon greater than 1/3 micrometer and it will be myelinated | |
| how does a progenitor cell produce either an oligodendrocyte or an astrocyte? | the progenitor cell will divide exactly 8 times in the presence of PDGF (platelet derived growth factor) it has a set number of PDGF receptors and after 8 divisions, it can no longer respond in the presence of CNTF (cellular neurotrophic factor), the daughter cells will become astrocytes. by default, they become oligodendrocytes | |
| what forms a scar in the CNS when an axon is damaged? | astrocytes | |
| what molecules do oligodendrocytes produce that are paralyzing neurites? | NOGO and neurite outgrowth factor | |
| when do schwann cells release Ach? | when a muscle is denervated, schwann cells will release Ach to stimulate it so it does not atrophy | |
| where does the different regenerative abilities of the CNS and PNS come from? | differences in the glia? | |
| where are ERB-2 and ERB-4 receptors expressed? | on radial glial cells | |
| what happens to radial glial cells after they stop interacting with neurons | they collapse, retract their processes, and become astrocytes or interneurons | |
| how do astrocytes control the potassium concentration in the extracellular space in the brain? | they take up K (from lots of AP) with their end feet on nodes of ranvier and dump K into the blood vessels via their end-feet on vessels | |
| how do astrocytes and neurons eat off the same plate? | astrocytes take up glucose from epithelial cells and turn it into lactate taking 2 ATP's from the 36. they then deliver lactate to the neuron's far reaching axons, etc. | |
| when the brain swells, which cells are swelling? | the glia. the neurons dont swell that much. |