membrane potential

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potential

 [po-ten´shal]
existing and ready for action, but not active.
electric tension or pressure.
action potential see action potential.
after-potential the period following termination of the spike potential.
auditory evoked potential in electroencephalography, changes in waves in response to sound; see also brainstem auditory evoked potential.
brainstem auditory evoked potential that portion of the auditory evoked potential that comes from the brainstem; abnormalities can be analyzed to evaluate comas, to support diagnosis of multiple sclerosis, and to detect early posterior fossa tumors.
cognitive event--related p's a diagnostic study that uses electroencephalographic equipment and a computer dedicated to analyze brain wave P300; this wave is a measure of the brain's active cognitive processing of information. The patient is instructed to complete a task that requires attention and information processing. A recording of brain wave activity as well as information related to cognitive function is produced.
diastolic potential the transmembrane potential of the cell during electrical diastole.
maximal diastolic potential the most negative level attained during the cardiac cycle by the cell membrane of a fiber that does not have a constant resting potential, occurring at the end of phase 3 of the action potential. In pacemaker cells this is a point of hyperpolarization.
membrane potential the electric potential that exists on the two sides of a membrane or across the wall of a cell.
resting potential (resting membrane potential) the difference in potential across the membrane of a cell when it is at rest, i.e., fully repolarized. In cardiac physiology this occurs during electrical diastole in pacemaker cells and continuously in nonpacemaker cells.
spike potential the initial, very large change in potential of the membrane of an excitable cell during excitation.
threshold potential the transmembrane potential that must be achieved before a membrane channel can open; it differs among the various cardiac membrane channels.
potential (omaha) in the omaha system, a problem modifier on the third level of the problem classification scheme, defined as the presence of health patterns, behaviors, or risk factors that may preclude optimal health even though specific signs and symptoms are absent.

mem·brane po·ten·tial

the potential inside a cell membrane, measured relative to the fluid just outside; it is negative under resting conditions and becomes positive during an action potential.

membrane potential

Etymology: L, membrana + potentia
the difference in electrical polarization or charge between two sides of a membrane or cell wall. Also called electric potential gradient.

membrane potential

Electrical potential due to the differences in the concentrations of ions on either side of a semipermeable membrane.

membrane potential

Cardiology The voltage difference between the inside and outside of resting excitable–neurons and muscle, not-yet depolarized cells

mem·brane po·ten·tial

(mem'brān pŏ-ten'shăl)
The potential inside a cell membrane, measured relative to the fluid just outside; it is negative under resting conditions and becomes positive during an action potential.

membrane potential

The difference in millivoltage between one side of a membrane and the other.

membrane potential

the potential difference between the two sides of a cell membrane. see NERVE IMPULSE.

membrane potential

electrical potential difference maintained across a cell membrane, with the inside negative to the outside:-110 mV to-130 mV in non-excitable cells, and -170 to -190 mV (the resting potential) in quiescent excitable cells (nerve and muscle). Due to unequal distributions mainly of potassium and sodium ions (the cell membrane being partially, but not equally, permeable to both) which in turn determines the relative movements of these ions down their respective diffusion gradients (potassium outwards and sodium inwards). The gradients are themselves maintained by the sodium-potassium (Na-K) pump which uses metabolic energy to transport the ions back 'uphill'. See also action potential, depolarization.

membrane

a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.

alveolocapillary membrane
a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries.
membrane-attack complex
complement components C5-C9 which form in terminal stage of either of the complement pathways and lead to cell lysis.
basilar membrane
the lower boundary of the scala media of the ear.
Bowman's membrane
a thin layer of basement membrane between the outer layer of stratified epithelium and the substantia propria of the cornea.
Bruch's membrane
the inner layer of the choroid, separating it from the pigmented layer of the retina.
membrane carrier
a mechanism in the cell membrane of epithelial cells in the intestinal mucosa which facilitates the rapid transport of for example glucose, into the cell and thus into the bloodstream.
cell membrane
plasma membrane (below).
membrane channels
see channel.
continuous membrane
the middle of the three membranes on the outside of the yolk of the hen egg.
cricothyroid membrane
the membrane connecting the thyroid cartilage to the cricoid cartilage. It is extensive in the horse and surgical incision through it allows access to the interior of the larynx.
Descemet's membrane
the posterior lining membrane of the cornea; it is a thin hyaline membrane between the substantia propria and the endothelial layer of the cornea.
drum membrane
tympanic membrane (below).
extraembryonic m's
those that protect the embryo or fetus and provide for its nutrition, respiration and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua and placenta.
extravitelline membrane
the outermost of the three membranes on the outside of the yolk of the hen egg.
false membrane
a membrane similar to the pseudomembrane; fibrinous exudates readily loosened from underlying tissue, as in croupous or pseudomembranous inflammation.
fenestrated membrane
one of the perforated elastic sheets of the tunica intima and tunica media of arteries.
fetal m's
see fetal membranes. See also extraembryonic membranes (above).
fibrous membrane
the strong, fibrous support layer in a joint capsule.
Henle's membrane
see henle's membrane.
hyaline membrane
1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle.
3. a homogeneous eosinophilic membrane lining alveolar ducts and alveoli, frequently found at necropsy in premature human infants. See also hyaline membrane disease.
hyoglossal membrane
a fibrous lamina connecting the under-surface of the tongue with the hyoid bone.
interosseous membrane
the membrane connecting the shaft of the fibula to the tibia.
limiting membrane
one that constitutes the border of some tissue or structure.
mucous membrane
the membrane covered with epithelium that lines many tubular organs of the body.
nictitating membrane
see membrana nictitans.
nuclear membrane
1. either of the membranes, inner and outer, comprising the nuclear envelope.
2. nuclear envelope.
olfactory membrane
the olfactory portion of the mucous membrane lining the nasal fossa.
periodontal membrane
perivitelline membrane
the innermost of the three layers on the outside of the yolk in the hen egg.
placental membrane
the membrane that separates the fetal from the maternal blood in the placenta.
plasma membrane
the membrane that encloses a cell; it is composed of phospholipids, glycolipids, cholesterol and proteins. The primary structure is a lipid bilayer. Phospholipid molecules have an electrically charged 'head' that attracts water and a hydrocarbon 'tail' that repels water; they line up side by side in two opposing layers, with their heads on the inner or outer surface of the membrane and their tails in the core, from which water is excluded. The other lipids affect the structural properties of the membrane. Proteins embedded in the membrane transport specific molecules across the membrane, act as hormone receptors, or perform other functions.
membrane potential
of a cell is the voltage difference across the cell membrane resulting from the differential concentrations of sodium and potassium on either side of the membrane. The resting potential, for example in a nerve cell, is altered by the temporary opening of the sodium channels in the membrane during an action potential, allowing a redistribution of the ions.
membrane proteins
the large number of proteins attached to a cell membrane. They include integral proteins, called also intrinsic, which are embedded in the phospholipid bi-layer of the cell membrane, and peripheral proteins, called also extrinsic, because they are loosely bound and can readily be extracted without damage to the cell membrane.
pupillary membrane
a vascular membrane which occupies the pupil in the embryo stage, completely covering the anterior surface of the lens but subsequently disappears. See also persistent pupillary membrane.
Reissner's membrane
the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.
Scarpa's membrane
tympanic membrane, secondary.
semipermeable membrane
one permitting passage through it of some but not all substances.
serosal membrane
see serous membrane (below).
serous membrane
the membrane lining the walls of the body cavities and enclosing the contained organs; it consists of mesothelium lying upon a connective tissue layer and it secretes a watery fluid.
shell membrane
the membrane on the outside of the soft contents of the hen egg and just inside the shell. It consists of two membranes close together, with an air cell in between.
synovial membrane
see synovial membrane.
membrane transport
transport of electrolytes across semipermeable membranes with the aid of a transporter.
unit membrane
the trilaminar structure of all cellular membranes (such as the plasma membrane, nuclear membranes, mitochondrial membranes, endoplasmic reticulum, lysosomes) as they appear in electron micrographs. The biochemical structure is a lipid bilayer.
wing membrane
the membrane comprising the wing of the bat.
yolk membrane
the membrane investing the yolk of the hen egg; it includes (from the inside out) the perivitelline, the continuous and the extravitelline membranes.

potential

1. existing and ready for action, but not active.
2. electric tension or pressure.

action potential
after-potential
the period following termination of the spike potential.
membrane potential
see membrane potential.
resting potential
the potential difference across the membrane of a normal cell at rest.
spike potential
the initial, very large change in potential of an excitable cell membrane during excitation.
zeta potential
a net negative charge.
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