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40 Cards in this Set
- Front
- Back
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What do the extensive endoplasmic reticulum and golgi apparatus do in neurons?
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produce secretory vesicles
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What is the role of the microtubules in neurons?
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transport neurotransmitter vesicles from site synthesis (soma) to site of storage
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What is the cell body of a neuron?
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soma
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what does the soma contain?
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cell nucleus and most of the intracellular organelles
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what is synthesized in the soma?
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proteins and neurotransmitter vesicles
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what is the one main protrusion in the neuron?
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axon
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What do axon branches do?
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give rise to a network of collateral axons
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What are axons specifically for?
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transmitting electrical signals known as action potentials
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What are dendrites?
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receiving points for incoming information from axons and other nerve cells
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What is the point of communication between the axon of one cell and a dendrite of another nerve cell called?
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synapse
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what are the components of a synapse?
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synaptic cleft, presynaptic membrane (axon) and post-synaptic membrane (dendrite)
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what do synaptic vesicles contain?
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neurotransmitters
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What is the function of neurotransmitters?
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chemical substances responsible for information transmission at the synapse
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where are synaptic vesicles synthesized?
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soma
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Where are synaptic vesicles stored?
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axon terminal
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What is the mitochondria's role in neurons?
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provide energy (ATP) for synthesis of neurotransmitters and for reuptake or enzymatic breakdown of neurotransmitters after their release
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What is the diffusion potential?
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-86 mV, caused by differential permeability of membrane "leak" channels to Na+ and K+
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What is the eletrogenic potential?
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-4 mV, caused by the sodium potassium pumps
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What is the net resting Em of large nerve fibers?
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-90 mV
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What happens when some stimulus acts on a nerve cell?
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permeability to Na increases, which causes it to diffuse into the cell
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What happens when Na+ diffuses into the nerve cell?
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It depolarizes
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What physical factors can depolarize cell membranes and initiate an action potential?
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pressure, vibrations, heat and cold, and tissue injury in sensory nerves
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What is the threshold level after depolarization for a nerve cell?
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-70 to -50 mV
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What happens when a nerve cell reaches -70 to -50 mV?
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"fast" Na channels open abruptly (voltage gating)
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What happens during repolarization?
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Na+ channels close and the PNa+ decreases, K+ channels open and diffuses OUT of the cell
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What is the duration of an action potential in a nerve fiber?
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0.5 to 1.0 milliseconds
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What is the absolute refractory period?
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another action potential CANNOT occur until the activation gates of Na+ channels reopen as the cell membrane returns to resting level (-90 mV)
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At what time would a nerve cell require higher stimulus for an action potential to occur?
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relative refractory period
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How is a nerve cell action potential propagated?
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"local currents" that cause depolarization of membrane adjacent to the point at which the action potential is happening
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What factors influence the velocity of propagation?
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diameter of axon, myelin
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How is velocity of propagation proportional to axon diameter?
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directly proportional
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Where is myelin produced?
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schwann cells (lie adjacent to nerve axons)
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True or false: the presence of myelin surrounding the axon decreases conduction velocity
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false, increases conduction velocity
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What are small breaks in the myelin sheath, and what are they for?
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Nodes of Ranvier, area that is not covered by myelin is where action potential can occur
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How often do Nodes of Ranvier occur?
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every 1 to 3 mm
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What is the movement of an action potential by the nodes of ranvier called?
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salutatory conduction
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What happens when there is decreased interstitial Ca++ in a nerve cell?
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hyper-excitability
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What happens when a nerve cell becomes hyper-excitable?
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threshold voltage for opening Na+ channels is lowered (more negative) - spontaneous depolarization may occur
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hypoexcitability in a nerve cell is caused by what?
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increased interstitial calcium
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What is the mechanism of action of local anesthetics?
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Bind to fast Na+ channels, keep gates in in-activated-close conformation, block action potential propagation
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