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52 Cards in this Set
- Front
- Back
what are the 4 different types of ion channels?
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Ligand gated
voltage gated background mechanosensitive |
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which ion channels are responsible for generating graded potentials?
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ligand gated
mechanosensitive |
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which ion channel is responsible for generating action potentials?
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voltage gated
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which ion channel is responsible for maintaining the resting membrane potential?
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background
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what causes the magnitude of the graded potential to change?
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the magnitude of the stimulus
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what is the difference in propagation paths between graded and action potentials?
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graded- bidirectional
action- unidirectional |
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what is the difference in conduction between action and graded potentials?
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graded- decremental and bidirectional
action- non-decremental and unidirectional |
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what is the difference in the location of graded potentials vs action potentials?
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graded- in the cell body or at a neuromuscular jxn
action- at the axon hillock and along the axon. or along the muscle fiber (sarcolemma) |
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what are the two types of postsynaptic, graded potentials?
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excititory- EPSP
inhibitory- IPSP |
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What is a GPSP and what does it mean?
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Grand Postsynaptic Potential
it is the culmination of all presynaptic stimuli at any given time |
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what is temporal summation?
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one way of bringing a post synaptic neuron to threshold.
it is the summation of repeated firings from a single presynaptic neuron |
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what is spatial summation?
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one way of bringing a post synaptic neuron to threshold.
it is the summation of repeated firings from multiple presynaptic neurons |
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what are the 4 types of voltage gated channels?
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Na+, K+, Ca+, and DHP
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what are the differences between a Na+ and K+ voltage gated ion channel?
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Na+ channels have an activation and inactivation gate. K+ channels only have activation gates.
the activation gates of Na+ channels open rapidly when threshold is reached. K+ channels are also triggered at threshold, but they have a delayed response |
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what events are triggered to happen when an action potential threshold is reached?
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Na+ and K+ activation gates are triggered to open
Na+ inactivation gates are triggered to close. |
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why doesnt the Na+ inactivation gate prevent siganal propagation if it is triggered to close at the same time as the activation gate?
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because the inactivation gate closes slowly
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why doesnt the K+ channel prevent signal propagation if its activation gate is triggered at the same time as Na+'s?
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because its response is delayed
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about how large must a graded potential be in order to create an action potential?
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10 to 15mV
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are depolarizing signals excititory or inhibitory?
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Excitatory
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are polarizing signals excititory or inhibitory?
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inhibitory
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where is the highest concentration of voltage gated ion channels located within a neuron?
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at the axon hillock
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during depolarization, what is the relationship between Na+ movement and K+ movement?
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Na+ movement into the cell exceeds the K+ movement out of the cell
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during repolarization, what is the relationship between Na+ movement and K+ movement?
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Na+ movement into the cell is less than the K+ movement out of the cell
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what type of feedback is established at the threshold of a Na+ channel?
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positive feedback
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what restores a cell to resting membrane potential after hyperpolarization?
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the Na+/K+ pump
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Why does tetrodotoxin prevent nerve impulses?
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it binds to the extracellular pore opening of voltage gated Na+ channels and prevents action potentials from occuring
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what event, within an action potential, are you inhibiting by blocking a voltage gated Na+ channel?
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depolarization
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how does topical lidocaine work?
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blocks voltage gated sodium channels
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what is the difference between an absolute and relative refractory period?
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Absolute- no stimulus can elicit an action potential
Relative- only a massive stimulus can elicit an action potential |
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why is it impossible to generate an action potential during an absolute refractory period?
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because all of the inactivation gates of voltage gated Na+ channels are closed. impossible to depolarize the membrane
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why is it harder than normal, but possible, to generate an action potential during the relative refractory period?
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do to the increased permiability of the membrane to K+ and the partial/residual inactivation of voltage gated Na+ channels
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what happens to muscles during hyperkalemic conditions?
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spontaneous muscle contractions that eventually lead to total muscle paralysis.
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Why do hyperkalemic conditions lead to muscle paralysis?
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high conc of ECF K+ prevents K+ channels from repolarizing the cell. this continuous state of depolarization causes Na+ channels to be inactivated, further decreasing the cells ability to create an action potential.
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what determines the speed of conduction?
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the diameter of a neuron and the degree of myelination.
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which sends a signal faster, a saltatory or contiguous axon?
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saltatory.
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why do saltatory axons send signals faster?
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because they are myelinated. the myelin acts as a capacitor and allows for signals to jump sections of the axon
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what do contiguous axons lack?
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myelination
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how much faster are myelinated fibers than unmyelinated ones of the same size?
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50 times
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what are the myelinating cells of the CNS?
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oligodendricytes
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what are the myelinating cells of the PNS?
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schwann cells
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If action potentials have an invariable intensity, how do you alter the intensity of a signal?
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by increasing or decreasing the frequency of impulse transmission
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how do plasma Ca+ levels effect the generation of action potentials?
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it alters the threshold of activation
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what happens to the threshold under high plasma Ca+ levels?
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the threshold is increased
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what happens to the threshold under low plasma Ca+ levels?
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the threshold is decreased
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why do plasma Ca+ levels have an effect on threshold?
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Ca+ can bind to phospholipids and make the plasma membrane less excitable, effectively decreasing the sensitivity of voltage gated Na+ channels
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What plasma components effect the amount of free calcium?
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Albumin
small anions (Phosphate, bicarbonate, and citrate) |
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what effect does hyperparathyroidism have on plasma Ca+ levels?
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increases Ca+ levels
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what effect does hypoparathyroidism have on plasma Ca+ levels?
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decreases Ca+ levels
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what effect does hyperparathyroidism have on plasma phosphate levels?
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decreases Phosphate levels
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what effect does hypoparathyroidism have on plasma phosphate levels?
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increases Phosphate levels
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What effect does an acidic plasma condition have on the amount of free Ca+ levels?
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H+ will compete with Ca+ binding sites on albumin and cause an increase in free plasma Ca+
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What effect does an alkaline plasma condition have on the amount of free Ca+ levels?
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The excess OH- will tie up free H+, reducing Ca+ binding site competition. This decreases plasma Ca+ concentrations
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