membrane potential (redirected from Graded potential)

potential /po·ten·tial/ (po-ten´shal)

1. existing and ready for action, but not active.

2. the work per unit charge necessary to move a charged body in an electric field from a reference point to another point, measured in volts.

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action potential  (AP) the electrical activity developed in a muscle or nerve cell during activity.

after-potential  afterpotential.

electric potential , electrical potential potential (2).

evoked potential  (EP) the electrical signal recorded from a sensory receptor, nerve, muscle, or area of the central nervous system that has been stimulated, usually by electricity.

membrane potential  the electric potential existing on the two sides of a membrane or across the cell wall.

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.

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membrane potential

n.

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.

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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.

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membrane

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

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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.

2. basement membrane.

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

see periodontium.

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.

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potential

1. existing and ready for action, but not active.

2. electric tension or pressure.

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action potential

see 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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membrane potential

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