151.L1.Lect14.15.Neur.12.11_13.13.Stu

Saltatory conduction of action potential myelinated

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Unformatted text preview: tatory conduction (of action potential) - myelinated neurons: ~150 m/sec - unmyelinated neurons: ~1m/sec 5. Release of neurotransmitter molecules from neuron 5. terminal (chemical signal; neurotransmission) terminal Fig. 43.2 Fig. Na+ channels open 1. Sensory stimulus (such as light) or neurotransmitter opens Na+ channels on a dendrite or cell body (ligand-gated) 2. Cell cytoplasm at (1) changes electrochemical gradient in positive direction by >20mV Campbell Figure 48.4 Fig. 43.2 Fig. Na+ channels open 1. Sensory stimulus (such as light) or neurotransmitter opens Na+ channels on a dendrite or cell body 2. Cell cytoplasm at (1) changes electrochemical gradient in a positive direction by >20mV 3. Voltage gated Na+ channels are progressively opened from site at (1) up to the axon hillock 4. Action potential WILL be generated at the axon hillock Campbell Figure 48.4 -50mV Before Na+ ion influx gets here Ll Fast responding Slow responding This action potential is an “all or none” event that begins at the axon hillock Campbell Figure 48.11 Slow responding http://outreach.mcb.harvard.edu/animations/actionpotential.swf -50mV Ll The influx of Na+ ions from the dendrites and cell body decrease the electrochemical gradient at the axon hillock to less than -50mV (moved >20mV in a positive direction) and above threshold Campbell Figure 48.11 http://outreach.mcb.harvard.edu/animations/actionpotential.swf +40mV Depolarization -50mV Ll Campbell Figure 48.11 http://outreach.mcb.harvard.edu/animations/actionpotential.swf Repolarization -50mV Ll Campbell Figure 48.11 http://outreach.mcb.harvard.edu/animations/actionpotential.swf -50mV -75mV Ll Undershoot: K+ channels are slow to close and neuron reaches about -75mV Na+ channels refractory to opening until electrochemical gradient is highly negative (such as below -50mV) http://outreach.mcb.harvard.edu/animations/actionpotential.swf Campbell Figure 48.11 -50mV Ll Na+/K+ ATPase pumps work together with other K+ “leak” channels to return the electrochemical gradient to -70mV Given the high concs. of ions in and arou...
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This note was uploaded on 04/02/2014 for the course BIO 151 taught by Professor Grinblat during the Spring '08 term at University of Wisconsin.

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