Glossary of Physiology Terms – E
Accumulation of fluid in the interstitial compartment, which usually leads to a visible swelling of the affected tissue.
Leading away from a region or structure of interest.
In the nervous system, efferent fibers (i.e., neurons) transmit information from the central nervous system to peripheral effector organs (i.e., muscles or glands). Therefore, the cells bodies of efferent neurons reside within the central nervous system, whereas their axonal projections exit the central nervous system to make synaptic contact with effector organs in the periphery. Efferent neurons are also referred to as motor neurons.
In the kidneys, the efferent arteriole carries blood away from the glomerular capillaries.
Related glossary terms/phrases:Afferent
Movement of a substance out of the cell.
Efflux is reported as a rate. It is the amount of substance that moves through a given area of the plasma membrane per unit time.
Related glossary terms/phrases:FluxInfluxUnidirectional fluxNet flux
ECG or EKG
A recording of the electrical activity of the heart measured by placing multiple (3 to 10) electrodes on the surface of the skin.
Electrogenic pumps are primary active transporters that hydrolyze ATP and use the energy released from ATP hydrolysis to transport ions across biological membranes leading to the translocation of net charge across the membrane.
For example, the Na+
ATPase (sodium pump) is an electrogenic pump because during every transport cycle, it transports 3 Na+
ions out of the cell and 2 K+
ions into the cell. This leads to the movement of one net positive charge out of the cell making this process electrogenic.
Related glossary terms/phrases:Electrogenic
An electrogenic transport process is one that leads to the translocation of net charge across the membrane. For example, ion channels such as Na+
, and Cl−
channels are electrogenic.
ATPase is electrogenic because for every ATP molecule hydrolyzed, 3 Na+
ions are transported out of the cell and 2 K+
ions are transported into the cell (leading to the translocation of one net positive charge out of the cell).
Many secondary active transporters
are also electrogenic. For example, the Na+
/glucose cotransporter (found in the small intestine and kidney proximal tubules), transports 2 Na+
ions and 1 glucose molecule into the cell across the plasma membrane (leading to the translocation of two net positive charges into the cell per transport cycle).
Electrophysiology is the study of the electrical properties of biological macromolecules, cells, tissues, and organs. Electrical signals such as voltage and/or current are generally measured. Examples include measuring changes in the membrane voltage of excitable cells (e.g., neurons, muscle cells, and some endocrine cells) during an action potential
. The current carrried by ions as they permeate the pore of ion channels can also be measured - both at the single-channel level (single-channel current), as well as the macroscopic current resulting from the activity of a population of channels. As another example, electrical measurements may involve recording voltage changes at the surface of the skin that result from the activity of skeletal muscles (electromyogram, EMG), cardiac myocytes (electrocardiogram, ECG), or neurons in the brain (electroencephalogram, EEG).
Endocrine cells are responsible for producing and releasing hormone
molecules into the bloodstream. Endocrine cells are typically grouped together in organs referred to as endocrine glands
Related glossary terms/phrases:Endocrine glandHormone
Endocrine glands contain clusters of endocrine cells
, whose function is to is to release hormones
into the bloodstream.
Endocrine glands are ductless glands in that their secretions do not enter a duct (as for example with salivary glands). Rather, endocrine glands release their secretions (i.e., messenger molecules) into the interstitial fluid in highly vascularized regions, where the molecules then enter the bloodstream. The chemical messenger molecule that is released into the bloodstream is referred to as a hormone.
Related glossary terms/phrases:Endocrine cellHormone
A type of secondary active transport
across a biological membrane in which a transport protein couples the movement of an ion (usually Na+
) down its electrochemical gradient to the movement of another ion or molecule against a concentration or electrochemical gradient. The ion moving down its electrochemical gradient is referred to as the driving ion. The ion/molecule being transported against a chemical or electrochemical gradient is referred to as the driven ion/molecule.
In exchange, the driving ion and the driven ion/molecule are transported across the biological membrane in opposite directions.
An example is the Na+
exchanger (NCX), which couples the movement of 3 Na+
ions into the cell down its electrochemical gradient to the movement of 1 Ca2+
ion out of the cell against its electrochemical gradient.
Exchange is also commonly referred to as antiport
Transport proteins that are involved in this type of transport are referred to as exchangers or antiporters.
Related glossary terms/phrases:Secondary active transportCotransport
Lecture notes on Secondary Active Transport
Refers to the ability of some cells to be electrically excited resulting in the generation of action potentials
. Neurons, muscle cells (skeletal, cardiac, and smooth), and some endocrine cells (e.g., insulin-releasing pancreatic β
cells) are excitable cells.
See also:Resting Membrane Potential - Introduction
Excretion refers to the elimination of waste substances from the body. The kidneys and lungs are mainly responsible for excreting metabolites and waste products.
Protrusion or bulging of one or both eyeballs out of the orbit. It may be caused by swelling of orbital tissue in response to trauma, or by hyperthyroidism (especially primary hyperthyroidism).
It is also referred to as exophthalmus, exophthalmia, proptosis, or exorbitism.
Other resources:Exophthalmos (Wikipedia)
Posted: Sunday, October 17, 2010
Last updated: Saturday, November 21, 2015