Potentials

Question 1

plateau

Answer 1

characteristic period in the action potential of the heart muscle cell, during which membrane potential is relatively constant


Question 2

all-or-none response

Answer 2

amplitude of action potentials induced in excitable cells does not depend on the strength of the stimulus only on the membrane properties and on the ionic gradients


Question 3

hyperpolarization and depolarization

Answer 3

a shift of the resting membrane potential toward more negative values – an increase

Question 4

afterhyperpolarization

Answer 4

hyperpolarization following an action potential


Question 5

repolarization

Answer 5

return of a membrane that has been depolarized to its resting membrane potential

Question 6

refractory period

Answer 6

period during and immediately after an action potential in which the membrane cannot be excited (absolute refractory period) or has an elevated threshold (relative refractory period)

Question 7

miniature end-plate potential

Answer 7

small, quantal changes of membrane potential in the neuromuscular synapse caused by the spontaneous presynaptic release of transmitter molecules

Question 8

Goldman-Hodgkin-Katz equation

Answer 8

approximate description of the resting membrane potential, based on the concentration and permeability of the three most important diffusible ions (Na+, K+, Cl-)

Question 9

space constant

Answer 9

externally induced and electrotonically conducted potential changes in the membrane decrease to 37% (1/e) after traveling a distance equal to the space constant


Question 10

time constant

Answer 10

time required for an externally induced potential change in the membrane to decrease to 37% (1/e) of the original potential
t

Question 11

compartmentalization

Answer 11

division of a space (e.g. cytoplasm) with limiting surfaces into subspaces with limited exchange of materials


Question 12

summation

Answer 12

in time and in space; adding up of the effects of two synaptic potentials occurring at the same synapse with short delay or in neighboring synapses concurrently

Question 13

electrochemical potential

Answer 13

combined effect of the electrical and concentration gradients on an ion

Question 14

Donnan equilibrium

Answer 14

electrochemical equilibrium that develops when two solutions are separated by a membrane permeable to only some of the ions in the solutions


Question 15

Nernst equation

Answer 15

equation for calculating electrochemical equilibrium conditions


Question 16

equilibrium

Answer 16

lowest energy state of a system that may result from opposing forces arising from within the system

Question 17

decremental (and electrotonic transmission)

Answer 17

electrical signal transmission in which signals are conducted with exponentially decreasing amplitude in space


Question 18

saltatory conduction

Answer 18

fast conduction of action potentials on myelinated axons; action potentials are only regenerated, thus delayed at nodes of Ranvier, while they pass through internodes by electrotonic conduction with minimal delay – action

Question 19

conductance

Answer 19

reciprocal value of the resistance


Question 20

overshoot

Answer 20

part of the action potential, where the membrane potential becomes positive potentials are “jumping from node to node”, hence the name