PSYC-115 FA5 Lecture Notes - Lecture 23: Afterhyperpolarization, University Of Manchester, Repolarization
13 Jun 2018
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April 20, 2018
Lecture 23
**on exam: what is a neuron? A cell
Slide 19 on exam: caricature of cell
●Molecular biology
○The neuron: cell with all the major components of all other cells
○Phospholipids-fat
■Polar head (charged)-hydrophilic (love water)
■Hydrophobic (avoid water)- non-polar tail (s) non-charged
○Lipid barrier: molecular bi-layer--the membrane will not let water through it
○***ions unequally distributed bc they are charged and can’t get through the membrane
○Semi-permeable barrier: because the membrane is primarily fat (due to the fatty acid
tails), charged chemical (i.e., ions) which have formed a chemical bond with water are
trapped in the water and are unable to pass through the membrane (because water can’t
pass through the fat). Consequently, ions on the inside or outside tend not to move across
membrane; permeable to fat but not water
○Consequence of stimulation: action potential (firing neuron)
○Terminology
■Resting potential: -70 mV
■Threshold: -55mV
■Depolarization: -55 to +30 mV)
■Repolarization (+30 to -70 mV)
■Afterhyperpolarization (-70 to -80 mV)
■Resting potential (caveat) (-70 mV)
○You fire a neuron by taking it to the threshold
●Protein channels- gateways to allow ions to move through
○Resting potential- charge is due to the unequal distribution of ions inside and outside the
membrane of the neuron
○Upward curve?
■Opening of Na+ channels with Na+ influx
■Varying thresholds allow for an auto cataclysmic reaction, i.e., as Na= enters it
further depolarizes the membrane that opens up other Na+ channels
■Holes open up to sodium at threshold so it can go inside the cell
■Channel resumes normal positions msec after repolarization
○Downward Curve?
■Delayed and slow (1-5 msec) opening of K+ channels with K+ efflux
Document Summary
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