threshold (redirected from pacing threshold)

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.) .

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thresh·old (thrshld, -hld)

n.

1. The place or point of beginning; the outset.

2. The lowest point at which a stimulus begins to produce a sensation.

3. The minimal stimulus that produces excitation of any structure, eliciting a motor response.

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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.

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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.

3. renal t.

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.

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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,

n See dose, threshhold.

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.

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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.

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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).

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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.

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threshold

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