| 释义 |
DictionarySeecitric acid cycleMedicalSeeCARDIAC CYCLE (ONE HEARTBEAT, PULSE 75): The outer circle represents the ventricles, the middle circle the atria, and the inner circle the movement of blood and its effect on the heart valves.cardiac cycleThe period from the beginning of one heartbeat to the beginning of the succeeding beat, including systole and diastole. Normally, the atria contract immediately before the ventricles. The ordinary cycle lasts 0.8 sec with the heart beating approx. 60 to 85 times a minute in the adult at rest. Atrial systole lasts 0.1 sec, ventricular systole 0.3 sec, and diastole 0.4 sec. Although the heart seems to be working continuously, it actually rests for a good portion of each cardiac cycle. A wart, typically found on the genitals, the perineum, the anus, or the mucosal surfaces of the vagina or mouth, usually spread by sexual contact. It is caused by various types of human papilloma virus and may be spread by physical contact with an area containing a wart. The spread of a wart from one labium to the other by autoinoculation is possible. The virus that causes the wart is usually transmitted sexually. Synonym: genital wartTreatmentTopically applied liquid nitrogen, imiquimod cream, fluorouracil, or podophyllin may prove effective; multiple treatments are usually needed, including occasionally surgery, electrosurgery, or laser ablation. Extremely large lesions (Buschke-Lowenstein tumor) may need radical excision. See: Cardiac Cycle illustrationcell cycleThe cycle of the growth and development of a cell. The cell cycle consists of mitosis, during which chromosomes actively divide to form two sister cells, and the interphase, during which the cell grows, begins to synthesize DNA, and prepares for chromosomal division. The interphase consists of several gap or G phases and the S (DNA Synthesis) phase. See: interphase; meiosis and mitosis for illus. cell growth cycleThe order of physical and biochemical events that occur during the growth of cells. In tissue culture studies, the cyclic changes are divided into specific periods or phases: the DNA synthesis or S period, the G2 period or gap, the M or mitotic period, and the G1 period. citric acid cycleKrebs cycle.Cori cycle See: Cori cycleduty cycleDuring chest compressions of a victim of cardiac arrest, the relative amount of time that the chest is compressed compared to the time that the chest is allowed to recoil to its fully inflated position. A cycle of 50% occurs when chest compression equals chest recoil. estrus cycleThe sequence from the beginning of one estrus period to the beginning of the next. It includes proestrus, estrus, and metestrus, followed by a short period of quiescence called diestrus. gastric cycleThe progression of peristalsis through the stomach. genesial cycle1. The period from puberty to menopause.2. The period of sexual maturity. glycolytic cycleThe cycle by which glucose is broken down in living tissue.initiated cycleIn assisted reproduction, any month when a woman is treated with drugs that stimulate the ovary to produce follicles. Krebs cycle See: Krebs cyclelife cycleAll of the developmental history of an organism, whether in a free-living condition or in a host (e.g., as a parasite that experiences part of its cycle inside another organism).  PHASES OF THE MENSTRUAL CYCLEmenstrual cycleThe periodically recurrent series of changes occurring in the uterus and associated sex organs (ovaries, cervix, and vagina) associated with menstruation and the intermenstrual period. The human cycle averages 28 days in length, measured from the beginning of menstruation. The menstrual cycle is, however, quite variable in length, even in the same person from month to month. Variations in the length of the cycle are due principally to variation in the length of the proliferative phase. See: illustrationThe menstrual cycle is divided into four phases characterized by histological changes that take place in the uterine endometrium. They are: Proliferative Phase: Following blood loss from the endometrium, the uterine epithelium is restored to normal; the endometrium becomes thicker and more vascular; the glands elongate. During this period, the ovarian follicle is maturing and secreting estrogens; with the estrogen stimulation, the endometrium hypertrophies, thickening and becoming more vascular, and the glands elongate. The phase is terminated by the rupture of the follicle and the liberation of the ovum at about 14 days before the next menstrual period begins. Fertilization of the ovum is most likely to occur in the days immediately following ovulation. Luteal or Secretory Phase: After releasing the ovum, the corpus luteum secretes progesterone. With the progesterone stimulation, the endometrium becomes even thicker; the glands become more tortuous and produce an abundant secretion containing glycogen. The coiled arteries make their appearance; the endometrium becomes edematous; the stroma becomes compact. During this period, the corpus luteum in an ovary is developing and secreting progesterone. This phase lasts 10 to 14 days. Premenstrual or Ischemic Phase: If pregnancy has not occurred, the coiled arteries constrict and the endometrium becomes anemic and shrinks a day or two before menstruation. The corpus luteum of the ovary begins involution. This phase lasts about 2 days and is terminated by the opening up of constricted arteries, the breaking off of small patches of endometrium, and the beginning of menstruation with the flow of menstrual fluid. Menstruation: The functional layer of the endometrium is shed. The menstrual cycle is altered by pregnancy, the use of contraception, intercurrent illnesses, diet, and exercise. nitrogen cycleA series of natural processes in which nitrogen is discharged from animal life into the soil; the nitrogen is taken up from the soil by nitrogen-fixing bacteria and converted to nitrates usable by plants for their nourishment; and in turn nitrogen is taken up by plant-eating animals.sleep-wake cycleThe amount of time spent asleep and awake and the cycle of that schedule from day to day.stimulated cycleA cycle in assisted reproduction in which a woman receives drugs to stimulate her ovaries for production of additional follicles. See: unstimulated cyclestretch-shortening cycleAn eccentric muscle contraction followed immediately by a concentric contraction of the same muscle group. The elastic potentiation that occurs during the eccentric phase increases the force of output of the concentric contraction. These exercises replicate functional movement patterns and are typically used in the advance phase of rehabilitation, particularly in sports rehab. Exercises incorporating this phenomenon are called plyometrics. See: plyometricstricarboxylic acid cycleKrebs cycle.unstimulated cycleA cycle in assisted reproduction in which a woman does not receive drugs to stimulate her ovaries for production of additional follicles. See: stimulated cycleurea cycleThe complex cyclic chemical reactions in some (ureotelic) animals, including humans, that produce urea from the metabolism of nitrogen-containing foods. This cycle, first described by Sir Hans Krebs, provides a method of excreting the nitrogen produced by the metabolism of amino acids as urea. Wald cycle See: Wald cyclecitric acid cycle See KREBS CYCLE.cycle, Krebs A series of reactions in which the intermediate products of carbohydrate, fat and protein metabolism are converted to carbon dioxide and hydrogen atoms (electrons and hydrogen ions). This cycle can only operate in the presence of oxygen. Further oxidation yields carbon dioxide, water and ATP. This cycle occurs in the mitochondria that are found in the cytoplasm of cells of living organisms. It forms one of the processes in the metabolism of glucose providing energy (stored in ATP) to maintain the vital functions of the cells (e.g. mitosis). This cycle represents the principal energy pathway of the corneal endothelium. Syn. citric acid cycle; tricarboxylic acid cycle. See mitosis.
| Table C9 Relationship between the minimum angle of resolution, the Snellen fraction and the equivalent spatial frequency of a sine wave | | | Snellen fraction | resolution (min of
arc) | | (m) | | (ft) | | Spatial frequency (cpd) | | 0.5 | | 6/3 | | 20/10 | | 60 | | 0.6 | | 6/3.6 | | 20/12 | | 50 | | 0.75 | | 6/4.5 | | 20/15 | | 40 | | 1.0 | | 6/6 | | 20/20 | | 30 | | 1.25 | | 6/7.5 | | 20/25 | | 24 | | 1.5 | | 6/9 | | 20/30 | | 20 | | 2.0 | | 6/12 | | 20/40 | | 15 | | 2.5 | | 6/15 | | 20/50 | | 12 | | 4.0 | | 6/24 | | 20/80 | | 7.5 | | 5.0 | | 6/30 | | 20/100 | | 6 | | 8.0 | | 6/48 | | 20/160 | | 3.8 | | 10.0 | | 6/60 | | 20/200 | | 3 | | 20.0 | | 6/120 | | 20/400 | | 1.5 |
">citric acid cycle the middle circle the atria, and the inner circle the movement of blood and its effect on the heart valves." href="javascript:eml2('davisTab', 'c610p0.jpg')"> CARDIAC CYCLE (ONE HEARTBEAT, PULSE 75): The outer circle represents the ventricles, the middle circle the atria, and the inner circle the movement of blood and its effect on the heart valves.cardiac cycleThe period from the beginning of one heartbeat to the beginning of the succeeding beat, including systole and diastole. Normally, the atria contract immediately before the ventricles. The ordinary cycle lasts 0.8 sec with the heart beating approx. 60 to 85 times a minute in the adult at rest. Atrial systole lasts 0.1 sec, ventricular systole 0.3 sec, and diastole 0.4 sec. Although the heart seems to be working continuously, it actually rests for a good portion of each cardiac cycle. A wart, typically found on the genitals, the perineum, the anus, or the mucosal surfaces of the vagina or mouth, usually spread by sexual contact. It is caused by various types of human papilloma virus and may be spread by physical contact with an area containing a wart. The spread of a wart from one labium to the other by autoinoculation is possible. The virus that causes the wart is usually transmitted sexually. Synonym: genital wartTreatmentTopically applied liquid nitrogen, imiquimod cream, fluorouracil, or podophyllin may prove effective; multiple treatments are usually needed, including occasionally surgery, electrosurgery, or laser ablation. Extremely large lesions (Buschke-Lowenstein tumor) may need radical excision. See: Cardiac Cycle illustrationcell cycleThe cycle of the growth and development of a cell. The cell cycle consists of mitosis, during which chromosomes actively divide to form two sister cells, and the interphase, during which the cell grows, begins to synthesize DNA, and prepares for chromosomal division. The interphase consists of several gap or G phases and the S (DNA Synthesis) phase. See: interphase; meiosis and mitosis for illus. cell growth cycleThe order of physical and biochemical events that occur during the growth of cells. In tissue culture studies, the cyclic changes are divided into specific periods or phases: the DNA synthesis or S period, the G2 period or gap, the M or mitotic period, and the G1 period. citric acid cycleKrebs cycle.Cori cycle See: Cori cycleduty cycleDuring chest compressions of a victim of cardiac arrest, the relative amount of time that the chest is compressed compared to the time that the chest is allowed to recoil to its fully inflated position. A cycle of 50% occurs when chest compression equals chest recoil. estrus cycleThe sequence from the beginning of one estrus period to the beginning of the next. It includes proestrus, estrus, and metestrus, followed by a short period of quiescence called diestrus. gastric cycleThe progression of peristalsis through the stomach. genesial cycle1. The period from puberty to menopause.2. The period of sexual maturity. glycolytic cycleThe cycle by which glucose is broken down in living tissue.initiated cycleIn assisted reproduction, any month when a woman is treated with drugs that stimulate the ovary to produce follicles. Krebs cycle See: Krebs cyclelife cycleAll of the developmental history of an organism, whether in a free-living condition or in a host (e.g., as a parasite that experiences part of its cycle inside another organism). PHASES OF THE MENSTRUAL CYCLEmenstrual cycleThe periodically recurrent series of changes occurring in the uterus and associated sex organs (ovaries, cervix, and vagina) associated with menstruation and the intermenstrual period. The human cycle averages 28 days in length, measured from the beginning of menstruation. The menstrual cycle is, however, quite variable in length, even in the same person from month to month. Variations in the length of the cycle are due principally to variation in the length of the proliferative phase. See: illustrationThe menstrual cycle is divided into four phases characterized by histological changes that take place in the uterine endometrium. They are: Proliferative Phase: Following blood loss from the endometrium, the uterine epithelium is restored to normal; the endometrium becomes thicker and more vascular; the glands elongate. During this period, the ovarian follicle is maturing and secreting estrogens; with the estrogen stimulation, the endometrium hypertrophies, thickening and becoming more vascular, and the glands elongate. The phase is terminated by the rupture of the follicle and the liberation of the ovum at about 14 days before the next menstrual period begins. Fertilization of the ovum is most likely to occur in the days immediately following ovulation. Luteal or Secretory Phase: After releasing the ovum, the corpus luteum secretes progesterone. With the progesterone stimulation, the endometrium becomes even thicker; the glands become more tortuous and produce an abundant secretion containing glycogen. The coiled arteries make their appearance; the endometrium becomes edematous; the stroma becomes compact. During this period, the corpus luteum in an ovary is developing and secreting progesterone. This phase lasts 10 to 14 days. Premenstrual or Ischemic Phase: If pregnancy has not occurred, the coiled arteries constrict and the endometrium becomes anemic and shrinks a day or two before menstruation. The corpus luteum of the ovary begins involution. This phase lasts about 2 days and is terminated by the opening up of constricted arteries, the breaking off of small patches of endometrium, and the beginning of menstruation with the flow of menstrual fluid. Menstruation: The functional layer of the endometrium is shed. The menstrual cycle is altered by pregnancy, the use of contraception, intercurrent illnesses, diet, and exercise. nitrogen cycleA series of natural processes in which nitrogen is discharged from animal life into the soil; the nitrogen is taken up from the soil by nitrogen-fixing bacteria and converted to nitrates usable by plants for their nourishment; and in turn nitrogen is taken up by plant-eating animals.sleep-wake cycleThe amount of time spent asleep and awake and the cycle of that schedule from day to day.stimulated cycleA cycle in assisted reproduction in which a woman receives drugs to stimulate her ovaries for production of additional follicles. See: unstimulated cyclestretch-shortening cycleAn eccentric muscle contraction followed immediately by a concentric contraction of the same muscle group. The elastic potentiation that occurs during the eccentric phase increases the force of output of the concentric contraction. These exercises replicate functional movement patterns and are typically used in the advance phase of rehabilitation, particularly in sports rehab. Exercises incorporating this phenomenon are called plyometrics. See: plyometricstricarboxylic acid cycleKrebs cycle.unstimulated cycleA cycle in assisted reproduction in which a woman does not receive drugs to stimulate her ovaries for production of additional follicles. See: stimulated cycleurea cycleThe complex cyclic chemical reactions in some (ureotelic) animals, including humans, that produce urea from the metabolism of nitrogen-containing foods. This cycle, first described by Sir Hans Krebs, provides a method of excreting the nitrogen produced by the metabolism of amino acids as urea. Wald cycle See: Wald cyclecitric acid cycle See KREBS CYCLE.cycle, Krebs A series of reactions in which the intermediate products of carbohydrate, fat and protein metabolism are converted to carbon dioxide and hydrogen atoms (electrons and hydrogen ions). This cycle can only operate in the presence of oxygen. Further oxidation yields carbon dioxide, water and ATP. This cycle occurs in the mitochondria that are found in the cytoplasm of cells of living organisms. It forms one of the processes in the metabolism of glucose providing energy (stored in ATP) to maintain the vital functions of the cells (e.g. mitosis). This cycle represents the principal energy pathway of the corneal endothelium. Syn. citric acid cycle; tricarboxylic acid cycle. See mitosis.
| Table C9 Relationship between the minimum angle of resolution, the Snellen fraction and the equivalent spatial frequency of a sine wave | | | Snellen fraction | resolution (min of
arc) | | (m) | | (ft) | | Spatial frequency (cpd) | | 0.5 | | 6/3 | | 20/10 | | 60 | | 0.6 | | 6/3.6 | | 20/12 | | 50 | | 0.75 | | 6/4.5 | | 20/15 | | 40 | | 1.0 | | 6/6 | | 20/20 | | 30 | | 1.25 | | 6/7.5 | | 20/25 | | 24 | | 1.5 | | 6/9 | | 20/30 | | 20 | | 2.0 | | 6/12 | | 20/40 | | 15 | | 2.5 | | 6/15 | | 20/50 | | 12 | | 4.0 | | 6/24 | | 20/80 | | 7.5 | | 5.0 | | 6/30 | | 20/100 | | 6 | | 8.0 | | 6/48 | | 20/160 | | 3.8 | | 10.0 | | 6/60 | | 20/200 | | 3 | | 20.0 | | 6/120 | | 20/400 | | 1.5 |
|