brain and behavior module 3

neurophysiology

is the study of the life processes within neurons that use electrical and chemical signals

action potential

a rapid electrical signal that travels along the axon of a neuron

neurotransmitter

a chemical messenger between neurons

ions

electrically charged molecules; two types: anions and cations

anions

negatively charged molecules

cations

positively charged molecules

intracellular fluid

ions are dissolved in this

micro-electrode

when inserted into a resting cell, it shows that it is more negative than the extracellular fluid

resting membrane potential

is -50 to -80 millivolts and shoes the negative polarity of the cell’s interior

extracellular fluid

ion channels

are proteins that span the membrane and allow ions to pass

gated ion channels

open and close in response to voltage changes, chemicals, or mechanical action

diffusion and electrostatic pressure

two opposing forces that drive ion movement

diffusion

causes ions to flow from areas of high to low concentration, along their concentration gradient

electrostatic pressure

causes ions to flow towards oppositely charged areas

sodium potassium pump

neurons use the ___________ to maintain resting potential

the sodium potassium pump

pumps three sodium ions out for every 2 K+ ions pumped in

the nernst equation

predicts the voltage needed to counterbalance the diffusion force pushing an ion across a membrane; this prediction is the resting membrane potential for that ion

action potential

brief but large changes in membrane potential; they originate in the axon hillock and are propagated along the axon

hyper polarization

is an increase in membrane potential-the interior of the membrane becomes even more negative

depolarization

is a decrease in membrane potential-the interior of the cell becomes less negative

hyper polarizing stimulus

produces a response that passively follows the stimulus; the greater the stimulus the greater the response

graded response

the change in potential

depolarizing stimulus

the same as a hyper polarizing one, to a point; if the membrane reaches the threshold-about 40mV-it triggers an action potential

all or none property of action potentials

the neuron fires at full amplitude or not at all-does not reflect increased stimulus strength

frequency

action potentials increase in ______ with increased stimulus strength

afterpotentials

changes in membrane potential after action potentials

Na+

action potentials are produced by the movement of ______ ions into the cell

voltage-gated Na+ channels

open in respone to the initial depolarization

refractory period

only some stimuli can produce an action potential

absolute refractory phase

no action potentials are produced

relative refractory phase

only strong stimulation can produce an action potential