(pēr'ē-ŏd )

[Gr. periodos, circuit, period of time]

1. The interval between two successive occurrences of any regularly recurring phenomenon or event; a cycle.
2. A colloquial expression for the menstrual flow.
3. The time a disease takes in running its course, or a stage of a disease, such as an incubation period.

absolute refractory p.The period of time in which a stimulus, no matter how strong, will not elicit a response after contraction of a muscle fiber or transmission of a nerve impulse by a neuron.

atrial blanking p.In cardiac electrophysiology, the period after catheter ablation of an arrhythmia when the arrhythmia may transiently recur.

benefit p.The period of time during which a benefit can be paid. The period may be for a government benefit (such as Social Security or Medicare) or from an insurance policy.

blanking p.The period after completion of a treatment when the body has not completely healed and the treatment has not yet matured. A patient's response to treatment during this period is not expected to represent the long-term response to the treatment.

childbearing p.The period in the life of the female puberty to menopause during which she is capable of procreation.

comment p.The period of time during which public discussion of health care regulations is invited, e.g., by federal health care agencies. When new governmental rules affecting health care are enacted, their potential effects are usually discussed in advance during open meetings. During this period members of the public, health care insurers, hospitals, clinics, and other agencies make known their interpretation of the effects of these new rules.

communicable p.In epidemiology and infectious diseases, the period of time during which an infectious agent is transmissible, directly or indirectly, from an infected person or animal to a susceptible person.

effective refractory p.In electrocardiography, an interval after the sparking of an action potential during which no additional potentials can be triggered regardless of the amplitude of the stimulus. The membrane is still in the repolarization phase of the previous action potential.

ejection p.Systole.

exclusivity p.In drug marketing, the period of time during which a manufacturer of a proprietary drug is allowed to exercise monopoly rights to its sales.

gestation p.The period of pregnancy from conception to parturition. Average length is 10 lunar months or 280 days measured from the onset of the last menstrual period, but length varies from 250 to 310 days.

SEE: gestation; pregnancy for table.

incubation p.Incubation (1).

infectious period The time during which someone with a contagious illness can pass the disease to others. The infectious period sometimes precedes the time when people experience symptoms of the disease.

isoelectric p.1The period of time when no electrical energy is produced in an action that normally produces an electric force, such as a muscle contraction.2In an electrocardiogram, the period of time when the electrical tracing is neither positive nor negative.

isometric p.Postsphygmic period.

last menstrual p.

ABBR: LMP

SEE: Naegeli rule.

latency p.Latent period

latent p.1The time between stimulation and the resulting response. SYN: lag; latency period.2Incubation (1).3The time from exposure to ionizing radiation to the first visible sign of the effects.

menstrual p.Menstruation.

missed p.Menstruation not occurring at the time it was expected or regularly occurs monthly.

monthly p.The time of menstrual flow.

open enrollment p.A time of the year when a health plan allows subscribers to choose new forms of health care coverage. During this period subscribers to one benefit plan may choose to disenroll from one component of a health plan and enroll in another.

patent p.The time during a parasitic disease that organisms are demonstrable in the body.

postsphygmic p.The short period in diastole when the ventricles are relaxed and no blood is entering. This lasts until the atrioventricular valves open. SYN: isometric period.

preclinical detectable p.Sojourn time

prepatent p.The period between the time of introduction of parasitic organisms into the body and their appearance in the blood or tissues.

presphygmic p.The short period in systole beginning with closing of the atrioventricular valves and ending with opening of the valves connecting the right and left ventricles to the pulmonary artery and aorta, respectively.

p. of reactivity In obstetrics, an initial episode of activity, alertness, and responsiveness to interaction, characteristic of the physiological and social responses of newborns to stimuli. The first period of reactivity begins with birth, lasts approx. 30 min, and ends when the infant falls into a deep sleep. Common assessment findings include transient tachypnea, nasal flaring, sternal retraction, crackles, tachycardia, and irregular heart rhythms. The second period of reactivity begins when the infant awakens and usually lasts 4 to 6 hr. Common assessment findings include signs of excessive respiratory and gastric mucus, hunger, apneic episodes, and the passing of a meconium stool.

relative refractory p.The brief period during repolarization of a neuron or muscle fiber when excitability is depressed. If stimulated, the cell may respond, but a stronger than usual stimulus is typically required.

safe p.The time during the menstrual cycle when conception is supposedly not possible. It typically extends from 5 days before ovulation to the day ovulation occurs. Because of the great variability of the menstrual cycle, it is either extremely difficult or impossible to predict the portion of the cycle in which intercourse may take place with no chance of conception. SYN: fertile interval.

silent p.1The time in the course of a disease in which the signs and symptoms are so mild as to be difficult to detect.2A pause in normally continuous electrical events such as an electrocardiogram (ECG) or electroencephalogram (EEG).3The period in a tendon reflex that immediately follows the contraction of the responding muscles during which the motor neurons do not respond to afferent impulses entering the reflex center.

sphygmic p.An obsolete term for systole.

wear p.1The maximum length of time that a radiation badge is worn before it is exchanged and the dose of radiation is measured.2The length of time that a transdermal medication delivery system is applied to the skin before it should be removed or replaced.

Wenckebach p.

SEE: under Wenckebach, Karel F..