Class Notes (1,036,669)
CA (594,154)
McGill (36,237)
PSYC (3,976)
PSYC 211 (290)
Lecture 4

PSYC 211 Lecture Notes - Lecture 4: Semipermeable Membrane, Extracellular Fluid, Axon TerminalPremium

2 pages46 viewsFall 2015

Department
Psychology
Course Code
PSYC 211
Professor
Yogita Chaudasama
Lecture
4

This preview shows half of the first page. to view the full 2 pages of the document.
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$
You're Reading a Preview

Unlock to view full version

Subscribers Only

Loved by over 2.2 million students

Over 90% improved by at least one letter grade.