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Lecture 4

PSYC 211 Lecture 4: 4
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by OneClass967593 , Fall 2015
2 Pages
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Fall 2015

Department
Psychology
Course Code
PSYC 211
Professor
Yogita Chaudasama
Lecture
4

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7
Lecture'#4'
The'Neuron’s'Electrical'Activity'
$
Measuring'Electrical'Potentials'of'Axons'
- an$action$potential$is$sent$from$the$soma$down$the$axon$to$the$terminal$button$$
- recording$from$an$axon$
o a$wire'electrode$is$placed$in$the$extracellular$fluid;$it$is$an$electrical$conductor$that$
provides$a$path$for$the$electricity$to$enter$or$leave$the$medium$
o a$fine$glass'microelectrode$is$inserted$into$the$axon.$This$records$activity$of$the$
neuronà$at$the$tip,$it$is$un-insulated$and$it$records$the$activity$inside$the$neuron$and$
then$
o the$oscilloscope,$a$sensitive$voltmeter,$turns$electrical$fluctuations$into$visible$signals$
Membrane'Potentials'
- the$difference$in$the$charge$between$the$inside$of$the$axon$and$the$extracellular$fluid$is$the$
membrane'potential'
- the'neurons'resting$potential'is$when$the'steady$membrane'potential$is$-70mV,$unless$it$is$
stimulated.$The$inside$of$the$axon$is$negative'
- in$its$resting$state,$the$neuron$is$polarized'
- we$can$stimulate$the$neuron$by$passing$a$positive$charge$through$another$microelectrode.$This$
changes$the$value$of$the$membrane$potential$(towards$0).$$The$neuron$is$now$depolarized'
- polarized$at$-70mV$
- depolarized$when$becoming$more$positive$and$peaks$at$+30mV$
- hyperpolarized$when$it$is$more$negative$than$-70mV$
The'Action'Potential'
- a$rapid$reversal$of$the$membrane$potential$(reversal$of$the$charge)$(i.e.$the$inside$of$the$
membrane$becomes$positive).$It’s$peak$is$+30mVà$really$negative$to$really$positive$
- the$membrane$quickly$restores$to$normal$(within$2$msec),$but$first$the$potential$overshoots$
and$the$resting$potential$becomes$hyperpolarized'(more'negative)$
- the$value$of$the$membrane$potential$that$must$be$reached$to$produce$an$action$potential$is$
called$the'threshold'of'excitation$
how$the$movement$of$ions$creates$electrical$charges$
- an$ion$is$a$charged$molecule.$Cations$are$positive,$and$anions$are$negative$
- forces$of$diffusion$move$ions$from$high$concentration$to$low$concentrations$

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Description
Lecture 4 The Neurons Electrical Activity Measuring Electrical Potentials of Axons an action potential is sent from the soma down the axon to the terminal button recording from an axon o a wire electrode is placed in the extracellular fluid; it is an electrical conductor that provides a path for the electricity to enter or leave the medium o a fine glass microelectrode is inserted into the axon. This records activity of the neuron at the tip, it is uninsulated and it records the activity inside the neuron and then o the oscilloscope, a sensitive voltmeter, turns electrical fluctuations into visible signals Membrane Potentials the difference in the charge between the inside of the axon and the extracellular fluid is the membrane potential the neurons resting potential is when the steady membrane potential is 70mV, unless it is stimulated. The inside of the axon is negative in its resting state, the neuron is polarized we can stimulate the neuron by passing a positive charge through another microelectrode. This changes the value of the membrane potential (towards 0). The neuron is now depolarized polarized at 70mV depolarized when becoming more positive and peaks at +30mV hyperpolarized when it is more negative than 70mV The Action Potential a rapid reversal of the membrane potential (reversal of the charge) (i.e. the inside of the membrane becomes positive). Its peak is +30mV really negative to really positive the membrane quickly restores to normal (within 2 msec), but first the potential overshoots and the resting potential becomes hyperpolarized (more negative) the value of the membrane potential that must be reached to produce an action potential is called the threshold of excitation how the movement of ions creates electrical charges an ion is a charged molecule. Cations are positive, and anions are negative forces of diffusion move ions from high concentration to low concentrations 7
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