Ch.4-How do neurons use electrical signals to transmit information

electricity

flow of electrons from a body

electrical potential

using stored electrical energy

-difference measured in voltage

electriacal stimulation

passing electrical current from the uninsulated tip of an electrode onto a nerve to produce beheavior-muscular contraction

electrical stimulation studies 

-electrical stimulation of the neocortex causes movement 

electoencephalogram (EEG)

graph of electrical activity from the brain, which is mainly composed of graded potentials from many neurons

-monitors sleep stages

electrographic seizures

periods of exessive neural synchrony

-causing seizures in people who do not have epilepsy

epilepsy causes

1. trauma

2. tumors 

3. infections 

4. structural abnormalities 

5. gentic mutations 

oscilloscope

a voltmeter with a screen sensitive enough to displag the minuscule electrical signals emanting from a nerve or neuron over time

mircoelectrodes

deliver electrical current to a single neuron as well as record from it

-record axona

what are postively and negatively charged ions called? 

postively charged ions are cations 

negatively charged ions are anions 

diffusion

movement of ions from an area of higher concentration to an area of lower concentration through random motion

-equal nunber of molecules

concentration gradient

relative abundance of sustance in space

-ions are intially highly concentrated where they enter top of a beaker of water, compared to bottom of beaker

-as time passes, concentration gradients flow down due to diffusion

voltage gradent 

difference in electric potential between two reigions that allows a flow of current if two regions are connected 

experimental results obtained over hundreds of years from electrical and more recently from electrical _implicated electrical activity in the nervous’s system’s flow of information

stimulation and recording

the electrical activity of neuronal axons entails the diffusion of ions. Ions may move down an and an

concentration gradient, voltage gradient

resting potential 

electrical charge across the insulating cell membrane in the abescence of stimulation, a strore of potential energy produced by a greater negative charge on the intracelluar side relative to the extracelluar side 

A decrease in the charge across motor neuron membrane results in

Depolarization

Action potential

Are all or none events

The process of converting sensory stimulation into neural messages is

Transduction

what does the resting potential vary from? 

-40 to -90 mV 

what ions take part in producing the resting potemtial?

sodium (Na+)

chloride (CI-)

sodium potassium pumps

protein molecules embedded in the cell membrane

chloride ions 

-move in and out of the cell through open channels in the membrance 

equilbrium (reversal) potential

the membrane potential of a individual ion, at which there is no net (overall) flow of that particular ion from one side of the membrane to the other

Nernst equation

calculates the equilibrium potential for an ion based on its charge and its concentration gradient across the membrance

graded potentials 

small voltage fluctuations acrosss the cell membrane 

hyperpolarization

-the charge of membrane increases

depolarization

the membrane charge decreases

where does hyperpolarization and depolarization take place 

neuronal dendrites and the soma (cell body) 

Potassium (K+) channels

-for the membrane to become hyperpolarized, its extracelluar side must become more postive which is acomplished by outward movement, or efflux of potassium ions

-potassium channels are open. sp,e resistemce to the outward flow of potassium ions remain

Chloride (CI-) channels

-chloride ions can pass through the membrane more ions remain on the outside than on the inside, so an influx of chloride ions due to decrease resistence to CI- flow results in brief increases of CI- inside the cell

sodium (Na+) channels 

-depolarization can be produced if normally closed sodium channel gates open to allow an influx of soidum ions 

tetraethylammonium (TEA)

-blocks potassium channels and hyperpolarization

terodotoxin

blocks sodium channels and depolarization

excitatory postsynaptic potentials 

depolarization of a neuron in response to stimulation, making the neuron more likely to produce an action potential 

-associated with the opening of sodium channels allowing an influx of sodium ions

inhibitory postsynaptic potential (IPSPs)

-hyperpolarization of neuron membrane in response to stimulation, making the neuron less likely to produce an action potential

-opening of chloride channels, which allows an influx of chloride ions

intial segment

-area near where the axon meets the cell body, which is rich in voltage-gated channels that generate the action potential