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136 Cards in this Set
- Front
- Back
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resting membrane potential of a cell
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-70 mV
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There is net excess of positive or negative charge inside cell? why?
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excess negative charge due to abundace of protein and nucleic acids
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which ion is the most permeable at rest?
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potassium
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which ion is least permeable at rest?
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sodium
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which two forces cause ions to want to move?
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concentration gradient
electical force |
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T/F Sodium is more concentrated outside the cell at rest.
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T
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T/F Potassium is more concentrated inside the cell at rest.
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T
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T/F Sodium has a tendency to want to move out of the cell at rest.
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F---it wants to move into cell at rest, down its conc. gradient
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T/F Potassium wants to move outside the cell at rest.
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T
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What is the Nernst Potential?
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tells us what the membrane potential would have to be for the electrical force to cancel out the concentration force
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What is driving force and how is it calculated?
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the net force on an ion to diffuse; is the difference between the membrane potential and the nernst potential for that ion
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what is the nernst potential for sodium? Calculate driving force with this information.
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+70mV; D.F. = 140 mV (difference between -70mV [membrane potential] and nernst potential)
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flux?
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permeability * driving force
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at rest the most permeable ion is...
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potassium
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T/F The membrane potential will most closely represent the nernst potential for the most permeable ion.
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T
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The Na/K pump pumps out how many Na ions and pumps in how many K ions?
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pumps out 3 Na ions for every 2 K ions it pumps in. (constantly moving net negative charge into cell)
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threshold for generating an action potential
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-50 mV
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what is depolarization
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Na becomes more permeable, leaks into cell "removing" membrane potential from -70mV to 0mV
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what is overshoot?
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membrane potential becomes positive, up to 30mV
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what is repolarization?
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membrane potential returns back to -70mV as potassium leaks out of cell
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what is afterhyperpolarization?
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membrane potential briefly drops below -70mV making it harder to reach threshold and generate another action potential (relative refractory period)
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how do we change an ions permeability?
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by opening/closing voltage gated ion channels
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T/F
sodium channels have two gates and potassium channels have one gate |
T
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what happens to both K and Na gates as threshold is reached?
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they open
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Why don't the gates cancel each other out at threshold?
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Na has much larger driving force and flows more rapidly into cell; K's gates open slower
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what causes afterhyperpolarization?
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Na gates closed; K gates still open
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T/F At rest, the inactivation gate is open and the activation gate is closed for Na channel.
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T
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Physiologically, what is the absolute refractory period.
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The period of time when the inactivation gate is closed.
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When does the inactivation gate reopen?
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When membrane potential gets below threshold (-50mV)
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When does the potassium gate open?
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when threshold is reached
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When does repolarization occur?
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When Na channels close (inactivation gate closes) and K gates fully open.
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When does activation gate close?
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during repolarization
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define antidromic
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an action potential that travels toward the cell body
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define orthodromic
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an action potential that travels toward axon terminal
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glial cells in the peripheral n.s.
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Schwann cells
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insulating cells in central n.s.
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oligodendrocytes
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type of pain via "c-fibers"
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achy dull pain
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T/F action potentials regenerate at the nodes of ranvier b/c this is where the voltage gates channels are located.
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T
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what is saltatory conduction
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the skipping of the action potential from node to node
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what prevents reverberation along an axon?
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the absolute refractory period---(the node previous to the location of the A.P. cannot depolarize again)
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T/F vesicles are loaded with Neurotransmitter via ATP at axon terminal
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T
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purpose of the presynaptic density
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holds vesicles in place
prevents premature fusing of vesicles and exocytosis of NT |
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two proteins that compose presynaptic density
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actin (tether ball post) and synapsin (rope from post into tether ball) [vesicle is tether ball]
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type of Ca channels located in region of synapse
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n-type Ca channels
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what happens to Ca channels when an AP arrives?
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they open, allowing Ca to enter the neuron flowing down its Ec gradient
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what happens when ca enters the neuron and binds to calcineurin?
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inactivates Ca channels
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what occurs when Ca enters neuron and binds to calmodulin?
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activates calmodulin-dependent protein kinase (CAM kinase)
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what does CAM-kinase do?
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phosphorylates synapsin which releases vesicle to fuse with membrane and dump NT
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purpose of "docking stations"?
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activated by Ca, membrane bound proteins that aid exocytosis of NT
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fates of NT after it is released?
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binds to receptors
diffuse out of cleft and into blood (washout) metabolized to diff. structure pumped back in |
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primary excitatory NT in CNS
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glutamate
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primary inhibitory NT of brain
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GABA
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primary inhibitory NT in spinal chord
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glycine
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type of channels in post-synaptic cells
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ligand-gated channels
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what is the ligand in the post-synaptic cell?
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the NT
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What is EPSP?
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excitatory post-synaptic potential; a gate opening for both K and Na---mV goes to -20mV, closer to threshold
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What is IPSP?
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inhibitory post-synaptic potential; gate permeable to Cl that results in hyperpolarization and far from threshold
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Two types of summation for IPSP and EPSP
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temporal and spatial summation
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what is temporal summation?
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a second psp occurs before complete decrement of the first psp (same location)
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what is spatial summation?
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multiple psp's are generated at same time in different locations.
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type of summation if an IPSP and an EPSP are summed
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spatial (different locations)
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where are most EPSPs generated?
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dendrites
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where are most IPSPs generated?
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soma or cell body
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Why are ISPSs more poweful than EPSPs?
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b/c of sites of origin, ipsps move a shorter distance, lose less charge and can inhibit multiple epsps
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n.s. utilized when aware of a decision
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somatic nervous system
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involuntary n.s.
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autonomic nervous system
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two parts of autonomic nervous system
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sympathetic (F or F)
parasympathetic (rest/dig) |
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sympathetic n.s. encompasses which portions of vertebral column
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thoracolumbar
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parasympathetic n.s. encompasses which portions of vertebral column
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craniosacral
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which nerve plays an important part in parasympathetic activity
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vagus nerve
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what is a ganglion?
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nucleus outside of cns
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symp. preganglionic fibers: long or short?
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short
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all preganglionic fibers: myelinated or unmyelinated?
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myelinated
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symp postganglionic fibers: long or short?
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long
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all postganglionic fibers: myelinated or unmyelinated?
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unmyelinated
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parasympathetic preganglionic fibers: long or short?
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long
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parasympathetic postganglionic fibers: long or short?
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short
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T/F: every axon exiting cns is myelinated
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T
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2 types of receptors for acetylcholine?
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nicotinic
muscarinic |
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T/F: the first synapse involving acetylcholine is a nicotinic receptor?
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T
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parasympathetic n.s.: type of receptor found on target cells following pre/post ganglionic travel
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muscarinic
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beta-1 receptors located in...
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heart
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beta-2 receptors located in....
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lungs
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beta-3 receptors located in...
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adipocytes
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two types of receptors for acetylcholine
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nicotinic
muscarinic |
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enzyme that makes acetylcholine
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choline acetyltransferase
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Ach receptor for somatic activity to muscle cells
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nicotinic
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Ach receptor type in TARGETcells of para/symp n.s.
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muscarinic
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Ach receptor type in 1st synapse in para/symp n.s.
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usually nicotinic
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Ach receptor type fo splanchnic nerve
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nicotinic
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enzyme that metabolizes Ach after exocytosis into choline and acetate
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choline esterases
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effect of beta-bungaro toxin (black widow spider venom)
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hyper-release of vesicles depleting #
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effect of botulism toxim
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prevent exocytosis
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hemicholinium
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deplete Ach--choline is scarce
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neostigmine, physostigmine, malathion and nerve gas: mechanism of action
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overstimulation; prolongs Ach exocytosis
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3 nicotinic agonists
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Ach
nicotine carbachol |
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3 nicotinic antagonists
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curare
succinyl choline rabies virus |
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3 muscarinic agonists
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Ach
muscarine pilocarpine oxotremorine |
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3 muscarinic antagonists
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atropine
scopolamine |
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how do nicotinic receptors work?
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ionophore---nonspecific conductance pore through the membrane (Na and K can pass--EPP)
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how do muscarinic receptors work?
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use of G-proteins as coupling agents
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inhibiting adenylate cyclase does what?
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dec. cAMP in cells
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guanylate cyclase stimulation..
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inc. cGMP in cells
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stimulate phospholiase c
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inc DAG, IP3, and Ca
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what is tyrosine used to make?
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catecholamines
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three catecholamines..
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NE
epi dopamine |
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what do the catecholamines share as a precursor?
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L-tyrosine
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enzyme that adrenal medulla cells express to make epinephrine.
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PMNT enzyme
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1) L-tyrosine to L-dopa via...
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tyrosine hydroxylase
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2) L-dopa to dopamine via...
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dopa decarboxylase
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3) dopamine to norepi via...
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dopamine beta hydroxylase
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4) norepi to epi via...
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PMNT enzyme
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action of alpha-methyl tyrosine, alpha methyl dopa, diethyldithiocarbamate:
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depletes transmitter
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action of amphetamines
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initial release but long term depletion (crash later)
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what is cortisol? what does it do?
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stress hormone; inc. epi synthesis in medulla
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action of cocaine, desipramine,
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increased NE in cleft but inhibits reuptake; long term depletion
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action of reserpine
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inhibits recycling of NE
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waste product of norepi in urine
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vanillylmandelic (VMA)
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two enzymes producing endproduct of norepi in urine
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monoamine oxidase (MAO)
catechol-o-methyl transferase (COMT) |
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effect of MAO inhibitors
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inc. DA, epi and Norepi in nerve terminals (more into vesicles)
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practical uses for MAOI's
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antidepressants and blood pressure regulators
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T/F Norepi/dopamine are NT in cns as well as pns
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T
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name of the source of noradrenergic neurons
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locus coeruleus
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source of dopamine in the brain
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substantia nigra
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5 subtypes of dopamine receptors
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D1 to D5
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what do dopamine receptors do?
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alter cAMP in target cells (inc. adenylate cyclase activity)
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more potent stimulus: epi or norepi?
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epi
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what are adrenergic receptors
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receptors for epi and norepi
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T/F adrenergic receptors are located in both the cns and pns
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T
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primary antagonist for alpha-adrenergic receptors
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phenoxybenzamine
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primary agonist for all beta-adrenergic receptors
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isoproterenol
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primary antagonist for all beta-adrenergic receptors
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propranolol
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agonist for beta-1 adrenergic receptors
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dobutamine
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antagonist for beta-1 adrenergic receptors
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atenolol
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where are beta-3 adrenergic receptors located?
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adipocytes
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beta-2 adrenergic receptor agonist
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albuterol
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