4 Action potentials

4 Action potentials - Signal transmission along axons ac0on...

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Signal’transmission’along’axons:’ac0on’poten0als’
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Fig. 48-8 Microelectrode Voltage’ recorder Reference’ electrode We’can’measure’the’trans-membrane’electrical’poten0al’diFerence’across’ the’plasma’membrane’by’making’an’electrode’that’has’a’very’0ny’0p’(less’ than’±.1’micrometers’in’diameter),’inser0ng’that’electrode’through’the’cell’ membrane,’and’comparing’the’electrical’²elds’recorded’by’that’electrode’ with’the’²elds’recorded’by’an’electrode’in’the’saline’outside’the’neuron.’ Saline’
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Fig. 48-9a S0muli’ +5±’ Membrane’poten0al’(mV)’ –5± Threshold’ Res0ng’ poten0al Hyperpolariza0ons –1±± ±’ 2’ 3 4’ Time’(msec)’ (a)’Graded’hyperpolariza0ons’ ± 1’ 5 Studying’a’neuron’using’the’ recording’set’up’on’the’previous’ slide,’we’discover’that’the’res0ng’ poten0al’is’about’6±’mV’inside’ nega0ve.’ If’we’pass’current’through’our’ electrode’to’add’more’nega0ve’ charge’to’the’inside’of’the’cell,’ our’electrode’records’a’ transmembrane’poten0al’( V m )’ that’is’more’inside-nega0ve’than’ the’res0ng’value.’ When’ V m ’becomes’more’inside- nega0ve’than’rest,’we’say’the’ membrane’is’ hyperpolarized .’
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Fig. 48-9b S0muli’ +5±’ Membrane’poten0al’(mV)’ –5± Threshold’ Res0ng’ poten0al Depolariza0ons –1±± ±’ 2’ 3 4’ Time’(msec)’ (b)’Graded’depolariza0ons’ 1’ 5’ ± If’we’pass’current’through’our’ electrode’to’add’more’posi0ve’charge’ to’the’inside’of’the’cell,’our’electrode’
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4 Action potentials - Signal transmission along axons ac0on...

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