phase

phase

 [fāz]

1. one of the aspects or stages through which a varying entity may pass.

2. In physical chemistry, any physically or chemically distinct, homogeneous, and mechanically separable part of a system.

phase 0 in cardiac physiology, the phase representing the upstroke of the action potential, in which rapid depolarization occurs after the cell reaches or is driven to threshold potential. It is the result of the opening of fast sodium channels and calcium channels.

phase 1 in cardiac physiology, the initial rapid repolarization phase of the action potential, caused by the closure of the fast sodium channels and an exodus of potassium from the cell.

phase 2 in cardiac physiology, the phase representing the plateau of the action potential, which contributes to the refractory period of the heart; there is a slow entry of calcium into the cell. It is the result of a balance between inward and outward currents and is particularly long in Purkinje and ventricular cells.

phase 3 in cardiac physiology, the terminal rapid repolarization phase of the action potential; it begins with the closing of the slow channels, resulting in an exodus of potassium from the cell and the activation of the sodium-potassium pump. The result is reestablishment of the normal resting potential.

phase 4 in cardiac physiology, the phase representing electrical diastole, i.e. the time between action potentials. It is the resting phase of the electrical cardiac cycle and is steadily maintained in nonpacemaker cells. In pacemaker cells, the membrane potential is normally reduced slowly until threshold potential is reached; if there is an outside stimulus, it may be driven down more rapidly.

continuous phase in a heterogeneous system, the component in which the disperse phase is distributed, corresponding to the solvent in a true solution. See also colloid.

disperse phase the discontinuous portion of a heterogeneous system, corresponding to the solute in a true solution.

G₁ phase a part of the cell cycle during interphase, lasting from the end of cell division (the M phase) until the start of DNA synthesis (the S phase).

G₂ phase a relatively quiescent part of the cell cycle during interphase, lasting from the end of DNA synthesis (the S phase) until the start of cell division (the M phase).

M phase the part of the cell cycle during which mitosis occurs; subdivided into prophase, metaphase, anaphase, and telophase.

S phase a part of the cell cycle near the end of interphase, during which DNA is synthesized; it comes between the G₁ and G₂ phases.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

phase

(fāz),

1. A stage in the course of change or development.
See also: stage, period.

2. A homogeneous, physically distinct, and separable portion of a heterogeneous system; for example, a mixture of oil, gum, and water are three phases of an emulsion.
See also: stage, period.

3. The time relationship between two or more events.
See also: stage, period.

4. A particular part of a recurring time pattern or wave form.
See also: stage, period.

[G. phasis, an appearance]

Farlex Partner Medical Dictionary © Farlex 2012

phase

(fāz)

n.

1. A characteristic form, appearance, or stage of development that occurs in a cycle.

2. A discrete homogeneous part of a material system that is mechanically separable from the rest, as is ice from water.

3. Any of the forms or states, solid, liquid, gas, or plasma, in which matter can exist, depending on temperature and pressure.

4. A distinct part in a course or development, as of a disease.

v.

To introduce, one stage at a time.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

phase

(1) One of a set of successive stages in a sequence, such as a step in the progression of a therapy from early testing in humans to postmarket evaluation, usually divided into four (or five) phases.
(2) A stage in the conduct of a clinical trial; because of the potential for confusion of various terms—phase, stage, period—epoch is preferred.

Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

phase

Medtalk A step in a process or cycle. See Acceleration phase, Burned-out phase, Chronic phase, Conceptive phase, Delayed sleep phase, Initial phase, Lag phase, Oepidal phase, Plateau phase, Prevascular phase, Proliferative phase, Recovery phase, Resting phase, Secretory phase, Shock phase, Stance phase, Swing phase, Take-off phase.

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

phase

(fāz)

1. A stage in the course of change or development.

2. A homogeneous, physically distinct, and separable portion of a heterogeneous system; e.g., oil, gum, and water are three phases of an emulsion.

3. The time relationship between two or more events.

4. A particular part of a recurring time pattern or wave form.
See also: stage, period

[G. phasis, an appearance]

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

phase 

The state of vibration of a light wave at a particular time. Light waves vibrating with the same frequency are said to be in phase if their peaks and troughs occur at the same time; otherwise they are said to be out of phase and one wave lags or precedes another by a phase difference (e.g. a fraction of a wavelength, or one wavelength, or a number of wavelengths). For waves exactly out of phase the phase difference is half a wavelength and for waves exactly in phase it is 0. See interference; wavelength.

Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann

phase

(fāz)

1. Stage in course of change or development.

2. Homogeneous, physically distinct, and separable portion of a heterogeneous system.

3. Time relationship between two or more events.

4. Particular part of a recurring time pattern or wave form.

[G. phasis, an appearance]

Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about phase

Q. What is the second phase of alcohol rehab? I guess the first one is well known... admitting you are addicted, but then what?

A. anybody??? advises about the second phase of rehab??

Q. what is the window phase for HIV?

A. The 'window' period for HIV infection describes the strong immune defense that reduces the number of viral particles in the blood stream, marking the start of the infection's clinical latency stage. Clinical latency can vary between two weeks and 20 years. During this early phase of infection, HIV is active within lymphoid organs, where large amounts of virus become trapped in the follicular dendritic cells. The surrounding tissues that are rich in CD4+ T cells may also become infected, and viral particles accumulate both in infected cells and as free virus. Individuals who are in this phase are still infectious.

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