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Glossary of Physiology Terms
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Definition:
An antagonist is a molecule that binds to a receptor, however, it does not activate the physiological response induced by the naturally occurring physiological ligand of the receptor. Moreover, once bound to the receptor, an antagonist prevents the physiological ligand from activating the receptor. Therefore, antagonist binding to a receptor prevents or blocks the action of the natural ligand.

For example, acetylcholine (ACh) is the naturally occurring physiological ligand that activates nicotinic and muscarinic acetylcholine receptors. Tubocurarine and succinylcholine are antagonists of the nicotinic ACh receptor (nAChR), and atropine is an antagonist of the muscarinic ACh receptor (mAChR).

Related glossary terms/phrases:
Agonist



Definition:
The ability of a tissue or organ to regulate its own function without extrinsic neural or hormonal input.

For example, in the kidneys, autoregulation ensures relatively constant blood flow and pressure through the kidney tubules in order to maintain a fairly constant glomerular filtration rate (GFR).



Definition:
An electrogenic transport process is one that leads to the translocation of net charge across the membrane. For example, ion channels such as Na+, K+, Ca2+, and Cl channels are electrogenic.

The Na+/K+ 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).



Definition:
Surgical removal of the fallopian tube.



Definition:
Amiloride inhibits epithelial Na+ channels (ENaC), and in doing so, it acts as a diuretic by inhibiting sodium reabsorption in the late distal convoluted tubules, connecting tubules, and collecting ducts in the kidneys.

Other resources:
Amiloride (Wikipedia)









Posted: Sunday, March 31, 2013
Last updated: Friday, August 28, 2015