Term
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Definition
| Difference in electrical charge between the inside and outside of a cell |
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Term
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Definition
| Electrode used to record a membrane potential, one tip placed inside neuron and another electrode placed outside neuron in extracellular fluid |
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Term
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Definition
| Occurs around -70mV; neuron is said to be polarized; means that the potential inside the neuron is 70mV less than outside the neuron |
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Term
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Definition
| More negative on the inside than outside |
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Term
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Definition
| Ions in neural tissue are in constant random motion and are more likely to spread out evenly because of concentration gradients |
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Term
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Definition
| Any accumulation of charges in one area tends to be dispersed by the repulsion among the like charges in the vicinity and the attraction of opposite charges concentrated elsewhere |
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Term
| Differential Permeability |
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Definition
| Passive property responsible for unequal distribution; K+ and Cl- ions easily pass through, Na+ passes through with difficulty, and protein ions do not pass through at all |
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Term
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Definition
| Specialized channel through which ions pass through the neural membrane |
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Term
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Definition
| Active transport mechanism that continually exchance 3 Na+ ions inside neuron for 2 K+ ions outside |
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Term
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Definition
| Decrease resting membrane potential from -70 to -67 mV |
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Term
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Definition
| Increase resting membrane potential from -70 to -72mV |
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Term
| Excitatory Postsynaptic Potentials |
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Definition
| Increase the likelihood that the neuron will fire (depolarize) |
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Term
| Inhibitory Postsynaptic Potentials |
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Definition
| Decrease the likelihoodd that a neuron will fire (hyperpolarize) |
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Term
| Characteristics of Transmission of Postsynaptic Potentials |
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Definition
1) Transmission is so rapid it can be assumed to be instantaneous
2) Transmission is decremental, they decrease in amplitude as they travel through the neuron, like an echo |
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Term
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Definition
| Conical structure at the junction between cell body and axon, formerly believed to be generation site of action potentials |
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Term
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Definition
| Sum of all graded EPSPs and IPSPs into one overall signal; makes neuron decide whether or not to fire |
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Term
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Definition
| Massive but momentary reversal of membrane potential from -70 to +50mV; all-or-none response |
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Term
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Definition
| Local EPSPs and IPSPs that are produced on different parts of the membrane sum to form a greater EPSPs or IPSPs |
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Term
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Definition
| Postsynaptic potentials produced in rapid succession at the same synapse sum to form a greater signal |
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Term
| Voltage-Activated Ion Channels |
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Definition
| Ion channels that open or close in response to changes in the level of the membrane potential; open due to influx of Na+ ions; K+ ions are pushed out of cell by conc. grad. and then by + charge |
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Term
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Definition
| 1 millisecond later, Na+ channels close, marking end of rising phase |
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Term
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Definition
| Continued efflux of K+ ions, because K+ ion channels close slowly, the neuron is left briefly hyperpolarized because too many K+ ions flow out |
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Term
| Absolute Refractory Period |
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Definition
| 1-2 milliseconds after initiation of an action potential in which it is impossible to elicit a 2nd one |
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Term
| Relative Refractory Period |
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Definition
| Possible for neuron to fire again, but only by applying higher-than-normal levels of stimulation |
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Term
| Refractory Period Responsibilities |
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Definition
1) APs normally travel along axons in only one direction; because the portions of an axon where a membrane potential just occurred are refractory, an AP can't reverse
2) Rate of neural firing is related to intensity of the stimulation; constant high stimulation leads to constant firing whereas intermediate levels wait through absolute and refractory periods |
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Term
| Difference Between Conduction of AP and EPSPs and IPSPs |
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Definition
1) Conduction of AP is nondecremental, they do not grow weaker as they travel along the axonal membrane
2) APs are conducted more slowly than postsynatpic potentials
3) Conduction of APs are active, IPSPs and EPSPs are passive
4) Wave of excitation triggered by generation of AP near axon hilock always passively spreads back through soma and dendrites |
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Term
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Definition
| If electrical stimulation of sufficient intensity is applied to terminal end of an axon, an action potential will be generated and will travel along the axon back to the cell body |
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Term
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Definition
| Axonal conduction in the natural direction from cell body to terminal buttons |
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