threshold


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threshold

 [thresh´old]
1. the level that must be reached for an effect to be produced, as the degree of intensity of stimulus that just produces a sensation.
2. that value at which a stimulus just produces a sensation, is just appreciable, or comes just within the limits of perception.
auditory threshold the slightest perceptible sound.
threshold of consciousness the lowest limit of sensibility; the point of consciousness at which a stimulus is barely perceived.
defibrillation threshold DFT; the minimum amount of energy in joules that will consistently terminate ventricular fibrillation.
fibrillation threshold the least intensity of an electrical impulse that will cause cardiac tissue to begin fibrillation.
pacing threshold the minimal electrical stimulus required to produce consistent cardiac depolarization.
renal threshold that concentration of a substance (threshold substance) in plasma at which it begins to be excreted in the urine.
sensing threshold in cardiac pacing terminology, the voltage of the minimum signal that consistently activates pulse generator function.

thresh·old

(thresh'ōld), Avoid the misspelling/mispronunciation threshhold.
1. The point at which a stimulus first produces a sensation.
2. The lower limit of perception of a stimulus.
3. The minimal stimulus that produces excitation of any structure, for example, the minimal stimulus eliciting a motor response.
Synonym(s): limen (2) [TA]
[A.S. therxold]

threshold

/thresh·old/ (thresh´old) the level that must be reached for an effect to be produced, as the degree of intensity of a stimulus that just produces a sensation, or the concentration that must be present in the blood before certain substances are excreted by the kidney (renal t.) .

threshold

(thrĕsh′ōld′, -hōld′)
n.
The point that must be exceeded to begin producing a given effect or result or to elicit a response: a low threshold of pain.

threshold

[thresh′ōld]
Etymology: AS, therscold
the point at which a stimulus is great enough to produce an effect. For example, a pain threshold is the point at which a person becomes aware of pain.

threshold

Medtalk The point, stage, or degree of intensity at which a particular effect occurs or action is taken. See Therapeutic threshold, Transfusion threshold.

thresh·old

(thresh'ōld)
1. The level of intensity at which a stimulus first produces a sensation.
2. The lower limit of perception of a stimulus.
3. The minimal stimulus that produces excitation of any structure.
4. Synonym(s): limen.
[A.S. therxold]

threshold

the level at which a STIMULUS results in a response and below which there is no response despite the application of a stimulus.

threshold

point at which a stimulus induces sensation, i.e. lowest limit of perception/lowest stimulus causing nerve excitation and axon potential generation

threshold 

The value of a stimulus that just produces a response. Syn. limen.
absolute threshold The minimum luminance of a source that will produce a sensation of light. It varies with the state of dark adaptation, the retinal area stimulated, the wavelength of light, etc. Syn. light threshold. See photochromatic interval.
contrast threshold See differential threshold.
corneal touch threshold See corneal touch threshold.
differential threshold The smallest difference between two stimuli presented simultaneously that gives rise to a perceived difference in sensation. The difference may be related to brightness, but also to colour and specifically to either saturation (while hue is kept constant) or hue (while saturation is kept constant). The differential threshold of luminance is equal to about 1% in photopic vision. Syn. contrast threshold (if the difference is one of luminance); just noticeable difference (jnd). See Weber's law; contrast sensitivity.
light threshold See absolute threshold.
movement threshold 1. The minimum motion of an object that can be perceived. 2. The speed at which an object moving between two points just appears to be moving. See hyperacuity; phi movement.
resolution threshold See limit of resolution.
stereo-threshold See stereoscopic visual acuity.

thresh·old

(thresh'ōld) Avoid the misspelling threshhold.
1. Point at which a stimulus first produces a sensation.
2. Lower limit of perception of a stimulus.
[A.S. therxold]

threshold (thresh´ōld),

n the lowest limit of stimulus capable of producing an impression on the consciousness or evoking a response in irritable tissue.
threshold dose,
threshold, high pain,
n higher than average capacity to withstand pain; exceptional pain tolerance.
threshold, low pain,
n lower than average capacity to withstand pain; minimal pain tolerance.
threshold, swallowing,
n the minimal stimulation required to initiate the reflex action of deglutition.

threshold

the level that must be reached for an effect to be produced, as the degree of intensity of stimulus which just produces a sensation.

threshold phenomenon
a theory explaining pruritus which states that some degree of pruritus is tolerated by a patient, but a small increase from an additional source raises the patient above their threshold and causes clinical signs.
renal threshold
that concentration of a substance in plasma at which it begins to be excreted in the urine.
threshold traits
heritable traits which have specific thresholds, e.g. four rather than three toes on a guinea pig's hindfeet, alive or dead at a specific age.
threshold unit
the distance between two thresholds when an inherited abnormality can occur at a number of levels, e.g. completely patent ductus arteriosus, through partial closure (ductus diverticulum) and complete closure. See also threshold traits (above).
References in classic literature ?
Then he went back to the threshold and sat down there, laying his well filled wallet at his feet.
Byles beheld this figure on the staircase, he shivered as with an ague, but continued to watch him steadfastly, until the gouty gentleman had reached the threshold, made a gesture of anguish and despair, and vanished into the outer gloom, whither the funeral music summoned him.
The old hunter had kept a keen eye on the movements of his three visitors, from the beginning, and had maintained his position, just without the threshold of the cabin, with a determined manner, that showed he was not to be easily driven from his post.
Miss Welland, evidently about to join the dancers, hung on the threshold, her lilies-of-the-valley in her hand (she carried no other bouquet), her face a little pale, her eyes burning with a candid excitement.
Ye know, also, that when mosques are builded, asses bear the stones and the cement, and cross the sacred threshold.
Katharine pushed the door half open and stood upon the threshold.
I pointed out to Miss Wendermott that you were in the prime of life and in magnificent condition, while her father was already on the threshold of the grave and drinking himself into a fever in a squalid hut in a village of swamps.
To his amazement, it was Penelope who stood upon the threshold.
The most furious had come to the Buytenhof at daybreak, to secure a better place; but he, outdoing even them, had passed the night at the threshold of the prison, from whence, as we have already said, he had advanced to the very foremost rank, unguibus et rostro, -- that is to say, coaxing some, and kicking the others.
Ferrari mastered her own throbbing heart; stepped over the threshold, conscious of her clammy hands, dry lips, and burning head; and stood in the presence of Lord Montbarry's widow, to all outward appearance as supremely self-possessed as her ladyship herself.
Advancing without conscious will of my own, I crossed the threshold of the door.
It was as if they had suddenly been stricken blind and deaf, and McArdle afterward said that for a moment he believed himself to have been killed by a stroke of lightning as he crossed the threshold.