potential /po·ten·tial/ (po-ten´shal)
potential
potential
1. existing and ready for action, but not active.
2. the work per unit charge necessary to move a charged body in an electric field from a reference point to another point, measured in volts.
action potential (AP) the electrical activity developed in a muscle or nerve cell during activity.
after-potential afterpotential.
electric potential , electrical potential potential (2).
evoked potential (EP) the electrical signal recorded from a sensory receptor, nerve, muscle, or area of the central nervous system that has been stimulated, usually by electricity.
membrane potential the electric potential existing on the two sides of a membrane or across the cell wall.
resting potential the potential difference across the membrane of a normal cell at rest.
spike potential the initial, very large change in potential of an excitable cell membrane during excitation.
po·ten·tial (p -t n shl)adj. Capable of being but not yet in existence; latent. n. 1. The inherent ability or capacity for growth, development, or coming into being. 2. The work required to bring a unit electric charge, magnetic pole, or mass from an infinitely distant position to a designated point in a static electric, magnetic, or gravitational field, respectively. 3. The potential energy of a unit charge at any point in an electric circuit measured with respect to a specified reference point in the circuit or to ground; voltage. |
potential
[pəten′shəl]
Etymology: L, potentia
an expression of the energy involved in transferring a unit of electric charge. The gradient or slope of a potential causes the charge to move. The movement of 1 coulomb of charge from a potential of V to a potential of V-1 volts requires 1 joule of energy.
potential
1. existing and ready for action, but not active.
2. electric tension or pressure.
action potential
see action potential.
after-potential
the period following termination of the spike potential.
membrane potential
see membrane potential.
resting potential
the potential difference across the membrane of a normal cell at rest.
spike potential
the initial, very large change in potential of an excitable cell membrane during excitation.
zeta potential
a net negative charge.
potential
The amount of energy required to transfer a unit of positive charge from one point in an electrical field to another (potential difference). It is typically measured in volts.
action potential The electric current generated in an axon of a nerve cell in response to a stimulus. The stimulus must be above a certain threshold value to have an effect. The sodium pump (or sodium/potassium pump) which transports most sodium ions outside the cell and potassium ions inside the cell ceases to function and the sodium ions rush in making the interior of the axon a positive voltage with respect to the outside. The voltage changes from about −70 mV to +40 mV and then falls rapidly back to the resting membrane potential as the sodium pump regains its effect. The whole process takes less than one millisecond and its amplitude is always the same (all or none law) for a given axon, whatever the magnitude of the stimulus. The action potential is followed by an inexcitable period called the refractory period, which usually lasts one or two milliseconds. The action potential travels as a wave in both directions from the point of stimulation and the speed is faster in myelinated than in unmyelinated nerve fibres. Syn. nerve impulse. See adaptation; Schwann cell; neuron; receptor potential; resting membrane potential; synapse.
dark potential of the eye See resting potential of the eye.
early receptor potential (ERP) This is an early rapid response that can be detected when the retina is stimulated with an intense flash of light, approximately 106 times brighter than that required to elicit the ERG. It is completed within 1.5 ms and is followed by the a-wave of the ERG. It is primarily, in man, a cone-generated potential. See electroretinogram.
graded potential A depolarization or a hyperpolarization (e.g. in the photoreceptors) generated by a neuron in response to a stimulus. The amplitude of the response varies with the intensity of the stimulus. If the neuron becomes depolarized to threshold an action potential is triggered in its axon.
membrane potential See resting membrane potential.
oscillatory p's . (OP) Subwaves of low amplitude but high frequency (70-140 Hz) superimposed on the b-wave of the electroretinogram. The amplitude of these oscillatory responses is usually enhanced by a filtering technique. These potentials are presumed to originate from the vicinity of the inner plexiform layer of the retina (probably the amacrine cells) and may reflect disturbances of that part of the retina.
receptor potential Difference in potential occurring in a receptor in response to a stimulus. This is a graded type of response with an amplitude proportional to the intensity of the stimulus (graded potential). The photoreceptors and the bipolar cells produce a receptor potential but, surprisingly, it is a hyperpolarization, i.e. the inside of the membrane becomes more negative with respect to the outside. The ganglion cells respond with action potentials. See action potential; rhodopsin.
resting membrane potential Difference in direct current potential between the inside and outside of a living cell. The inside of the cell is usually about −70 mV compared to the outside, but this value depends on the quantity of potassium (mainly), sodium and chloride ions on both sides of the membrane, and the permeability to these ions of the membrane itself. Syn. membrane potential; transmembrane potential. See depolarization; hyperpolarization; action potential; tonus.
resting potential of the eye A direct current potential which exists between the anterior and posterior poles of the eye, the cornea being positive relative to the back of the eye. It is of the order of several mV in humans. This potential is used in recording the electrooculogram. Syn. dark potential of the eye; standing potential of the eye. See electrooculogram.
standing potential of the eye See resting potential of the eye.
standing potential See electrooculogram.
transmembrane potential See resting membrane potential.
visual evoked cortical potential (VECP) An electrical potential measured at the level of the occipital cortex in response to a light stimulation. Recording requires repetition of the stimulus and a computer synchronized with the onset of that stimulus, to average out the background noise produced by the spontaneous brain potentials (e.g. alpha, beta, delta, theta waves). This potential has clinical application and is used to objectively measure refraction, visual acuity, amblyopia, binocular anomalies and help in the diagnosis of some demyelinating diseases (e.g. multiple sclerosis), etc. Many abbreviations are also used, although they are not strictly correct. They are EP (evoked potential), VEP (visually evoked potential), VER (visual evoked response), and pVER (indicating that this potential is pattern-elicited). See objective accommodation; artifact; electrodiagnostic procedures.
action potential The electric current generated in an axon of a nerve cell in response to a stimulus. The stimulus must be above a certain threshold value to have an effect. The sodium pump (or sodium/potassium pump) which transports most sodium ions outside the cell and potassium ions inside the cell ceases to function and the sodium ions rush in making the interior of the axon a positive voltage with respect to the outside. The voltage changes from about −70 mV to +40 mV and then falls rapidly back to the resting membrane potential as the sodium pump regains its effect. The whole process takes less than one millisecond and its amplitude is always the same (all or none law) for a given axon, whatever the magnitude of the stimulus. The action potential is followed by an inexcitable period called the refractory period, which usually lasts one or two milliseconds. The action potential travels as a wave in both directions from the point of stimulation and the speed is faster in myelinated than in unmyelinated nerve fibres. Syn. nerve impulse. See adaptation; Schwann cell; neuron; receptor potential; resting membrane potential; synapse.
dark potential of the eye See resting potential of the eye.
early receptor potential (ERP) This is an early rapid response that can be detected when the retina is stimulated with an intense flash of light, approximately 106 times brighter than that required to elicit the ERG. It is completed within 1.5 ms and is followed by the a-wave of the ERG. It is primarily, in man, a cone-generated potential. See electroretinogram.
graded potential A depolarization or a hyperpolarization (e.g. in the photoreceptors) generated by a neuron in response to a stimulus. The amplitude of the response varies with the intensity of the stimulus. If the neuron becomes depolarized to threshold an action potential is triggered in its axon.
membrane potential See resting membrane potential.
oscillatory p's . (OP) Subwaves of low amplitude but high frequency (70-140 Hz) superimposed on the b-wave of the electroretinogram. The amplitude of these oscillatory responses is usually enhanced by a filtering technique. These potentials are presumed to originate from the vicinity of the inner plexiform layer of the retina (probably the amacrine cells) and may reflect disturbances of that part of the retina.
receptor potential Difference in potential occurring in a receptor in response to a stimulus. This is a graded type of response with an amplitude proportional to the intensity of the stimulus (graded potential). The photoreceptors and the bipolar cells produce a receptor potential but, surprisingly, it is a hyperpolarization, i.e. the inside of the membrane becomes more negative with respect to the outside. The ganglion cells respond with action potentials. See action potential; rhodopsin.
resting membrane potential Difference in direct current potential between the inside and outside of a living cell. The inside of the cell is usually about −70 mV compared to the outside, but this value depends on the quantity of potassium (mainly), sodium and chloride ions on both sides of the membrane, and the permeability to these ions of the membrane itself. Syn. membrane potential; transmembrane potential. See depolarization; hyperpolarization; action potential; tonus.
resting potential of the eye A direct current potential which exists between the anterior and posterior poles of the eye, the cornea being positive relative to the back of the eye. It is of the order of several mV in humans. This potential is used in recording the electrooculogram. Syn. dark potential of the eye; standing potential of the eye. See electrooculogram.
standing potential of the eye See resting potential of the eye.
standing potential See electrooculogram.
transmembrane potential See resting membrane potential.
visual evoked cortical potential (VECP) An electrical potential measured at the level of the occipital cortex in response to a light stimulation. Recording requires repetition of the stimulus and a computer synchronized with the onset of that stimulus, to average out the background noise produced by the spontaneous brain potentials (e.g. alpha, beta, delta, theta waves). This potential has clinical application and is used to objectively measure refraction, visual acuity, amblyopia, binocular anomalies and help in the diagnosis of some demyelinating diseases (e.g. multiple sclerosis), etc. Many abbreviations are also used, although they are not strictly correct. They are EP (evoked potential), VEP (visually evoked potential), VER (visual evoked response), and pVER (indicating that this potential is pattern-elicited). See objective accommodation; artifact; electrodiagnostic procedures.
potential
Vox populi 1. The difference in electric charge between 2 points in a circuit, expressed in volts or mV. See Action potential, Evoked potential, Inhibitory post-synaptic potential, Late potential, Membrane potential, Spike
potential, Ventricular late potential, Zeta potential 2. The inherent capacity to occur. See Biological hazard potential, Biopotential, Biotic potential, Chemical potential, Health potential, Maximum life-span potential.
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