neural communication: action potential
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Neural Communication: Action Potential. Lesson 10. Neural Signaling: Axon. Action Potentials propagated electrical signal regenerated Large & rapid changes in E m depolarization repolarization ~. Action Potentials. Electrically-gated channels or voltage-gated Characteristics - PowerPoint PPT PresentationTRANSCRIPT
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NeuralCommunication: Action Potential
Lesson 10
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Neural Signaling: Axon
Action Potentials propagated electrical signal regenerated
Large & rapid changes in Em depolarization repolarization ~
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Action Potentials Electrically-gated channels
or voltage-gated Characteristics
all-or-none relatively slow non-decremental ~
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Threshold of Excitation
also: threshold potential Triggered at axon hillock
point of decision integration
Threshold potential Depolarization; approximately 10 mV EPSPs AP ~
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-70
-60
0
+40
-80
Time
Em
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Depolarization
Na+ influx
C & E gradientsdrive Na+ into cell
Em
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Na+
K+
+
-
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Na+
K++
-
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Repolarization
K+ efflux Em
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Na+
K++
-
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Na+
K++
-
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After- hyperpolarization
Em
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Refractory Period
After AP time-out prohibits or resists AP absolute & relative ~
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Refractory Period
Absolute refractory period Na+ channels deactivate will not trigger AP must reset one-way transmission of signal
Ball & Chain Model ~
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Na+ channel deactivation
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Na+ channel deactivation
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Refractory Period
Relative refractory period during after-hyperpolarization requires greater depolarization to
reach threshold ~
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Frequency Code
Intensity of stimulus frequency of APs Pattern
Type of stimulus Brain area that receives signal Visual, auditory, pain, etc. Doctrine of Specific Nerve Energies ~
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FREQUENCY CODE
1.
2.
3.
Weak stimulus
Moderate stimulus
Strong stimulus
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Saltatory Conduction
Myelinated neurons oligodendrocytes & Schwann cells
Long distances transmission APs relatively slow, regenerates EPSPs - fast, decremental
Saltatory: combines both types of current speed without loss of signal ~
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Saltatory Conduction
Nodes of Ranvier action potentials no myelin
Myelinated portions passive current decremental but triggers AP at
next node ~
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Saltatory Conduction
Nodes of Ranvier
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PSPs vs APs
GradedSummation
longer duration10-100 msec
chemical-gated passive spread
instantaneousdecremental
All-or-none
short1-2 msec
voltage-gated propagated
slownondecremental