A reflex mechanism involves a receptor organ, an effector organ, and some type of communication network. Ivan Pavlov unintentionally launched the study of conditioning by establishing a way of producing what he called "conditional reflexes", i.e. reflexes that would only be seen conditional on previous experiences of the subject. ...

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Reflex action, Reflex action - Explanation, Reflex action - Reaction time, Reflex action - Mechanism, Reflex action - Human reflexes, Reflex action - Significance

Read more here: » Reflex action: Encyclopedia II - Reflex action - Mechanism

See also:

Piroxicam, Piroxicam - Mechanism of action, Piroxicam - Adverse effects

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Typically, the bolt consists of a tube of metal inside of which the firing mechanism is housed, and which has at the front or rear of the tube several metal knobs, or "lugs", which serve to lock the bolt in place. The operation can be done via a rotating bolt, a lever, or a number of systems. For example, one setup is a straight-pull design that use a rotating bolt, such as the German Blaser R93 rifle. Straight pull designs have seen a great deal of use, though manual turn-bolt designs are what most commonly thought of in reference to a bolt ...

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Bolt action, Bolt action - Mechanics, Bolt action - Loading, Bolt action - History

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Clonidine is a centrally-acting alpha-2 agonist. It selectively stimulates receptors in the brain that monitor catecholamine levels in the blood. These receptors close a feedback loop that begins with descending sympathetic nerves from the brain that control the production of catecholamines (epinephrine, also known as adrenaline, and norepinephrine) in the adrenal medulla. By fooling the brain into believing that catecholamine levels are higher than they really are, clonidine causes the brain to reduce its signals to the adrenal medulla, whi ...

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Clonidine, Clonidine - Mechanism of action, Clonidine - Administration

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The mechanism of action of tramadol has yet to be fully elucidated, but it is believed to work through modulation of the GABAergic, noradrenergic and serotonergic systems. Tramadol [and its metabolite, known as M1] have been found to bind to μ-opioid receptors (thus exerting its effect on GABAergic transmission), and to inhibit reuptake of 5-HT and noradrenaline. The second mechanism is believed to contribute since the analgesic effects of tramadol are not fully antagonised by the μ-opioid receptor antagonist naloxone. Although irrelevant to its mechanism of action, tramadol, unlike morphine, ...

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Tramadol, Tramadol - Mechanism of action, Tramadol - Dependence, Tramadol - Proprietary preparations

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Inside the red blood cells, the parasite must degrade the hemoglobin for the acquisition of all the nutrients the parasite needs to survive and multiplicate inside the cell. During this process, the parasite produces the toxic and soluble molecule heme. To avoid destruction by this molecule, the parasite aggregates heme to form hemozoin, an insoluble and non-toxic molecule. Chloroquine interferes with this process and prevents the formation of hemazoine, which in turn leaves heme in an uncrystallised form. This has a toxic effect to the ...

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Chloroquine, Chloroquine - Pharmacology, Chloroquine - Mechanism of action

Read more here: » Chloroquine: Encyclopedia II - Chloroquine - Mechanism of action

Pemetrexed is chemically similar to folic acid and is in the class of chemotherapy drugs called folate antimetabolites. It works by inhibiting three enzymes used in purine and pyrimidine synthesis—thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyl transferase (GARFT). By inhibiting the formation of precursor purine and pyrimidine nucleotides, pemetrexed prevents the formation of DNA and RNA, which are required for the growth a ...

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Pemetrexed, Pemetrexed - Mechanism of action, Pemetrexed - Clinical use

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Riluzole has several actions: Sodium channel blockade High-voltage calcium channel blockade N-methyl-D-aspartate (NMDA)/glutamate receptor blockade Riluzole preferentially blocks TTX-S sodium channels, which are associated with damaged neurons. This reduces influx of calcium ions and indirectly prevents stimulation of glutamate receptors. Together with direct glutamate receptor blockade, the effect of the neurotransmitte ...

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Riluzole, Riluzole - Mechanism of action, Riluzole - Studies of efficacy, Riluzole - Clinical use

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Meloxicam is an NSAID and, as such is a cyclooxygenase (COX) inhibitor. It is generally marketed under the name MOBIC. Meloxicam has been shown, especially at its low therapeutic dose, to selectivly inhibit COX-2 over COX-1. Main article: Non-steroidal anti-inflammatory drug ...

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Meloxicam, Meloxicam - Mechanism of action, Meloxicam - Adverse effects, Meloxicam - Approval status

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Dofetilide works by selectively blocking the rapid component of the delayed rectifier outward potassium current (IKr). This causes prolongation of the effective refractory period of accessory pathways (both anterograde and retrograde conduction in the accessory pathway). It is this selective action on accessory pathways that makes dofetilide effective in the treatment of atrial fibrillation and flutter. Dofetilide does not effect Vmax (The slope of the upstroke of phase 0 depolarization), condu ...

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Dofetilide, Dofetilide - Mechanism of action, Dofetilide - Metabolism, Dofetilide - Side effects, Dofetilide - Clinical use

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Isoniazid is a prodrug and must be activated by bacterial catalase. The active form inhibits the synthesis of mycolic acid in the mycobacterial cell wall. Isoniazid reaches therapeutic concentrations in serum, cerebrospinal fluid (CSF), and within caseous granulomas. Isoniazid is metabolized in the liver via acetylation. There are two forms of the enzyme responsible for acetylation, so that some patients metabolize the drug quicker than others. Hence, the half-life is bimodal with peaks at 1 hour and 3 hours in the US population. The metabolites are excreted in the urine. Doses do not usua ...

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Isoniazid, Isoniazid - Mechanism of action, Isoniazid - Side effects, Isoniazid - Reference

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Vancomycin acts by inhibiting proper cell wall synthesis in Gram-positive bacteria. The mechanism inhibited, and various factors related to entering the outer membrane of Gram-negative organisms mean that vancomycin is not active against Gram-negative bacteria. Specifically, vancomycin prevents incorporation of N-acetylmuramic acid (NAM)- and N-acetylglucosamine (NAG)-peptide subunits from being incorporated into the peptidoglycan matrix; which forms the major ...

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Vancomycin, Vancomycin - Mechanism of action, Vancomycin - Therapeutic considerations, Vancomycin - Clinical indications, Vancomycin - Resistance

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Amplification of ErbB2 occurs in 30% of early-stage breast cancers (Bange et al 2001). It encodes the transmembrane tyrosine kinase p185-erbB2 glycoprotein. Although the signaling pathways induced by the erbB2 receptor are incompletely characterized, it is thought that activation of the PI3K/Akt pathway is important. This pathway is normally associated with mitogenic signaling involving the MAPK pathway. In cancer growth producing signals from erbB2 are constitutively transmitted, promoting invasion, survival and angiogenesis of cells ...

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Trastuzumab, Trastuzumab - Mechanism of action, Trastuzumab - Impact, Trastuzumab - Side effects, Trastuzumab - History

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Beta-endorphin is released into the blood (from the pituitary gland) and into the spinal cord and brain from hypothalamic neurons. The beta-endorphin that is released into the blood cannot enter the brain in large quantities because of the blood-brain barrier. The physiological importance of the beta-endorphin that can be measured in the blood is far from clear: beta-endorphin is a cleavage product of POMC which is the precursor hormone for adrenocorticotrophic hormone (ACTH), so it will be released whenever ACTH is released. The behevioral ...

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Endorphin, Endorphin - History, Endorphin - Molecular biology, Endorphin - Mechanism of action, Endorphin - Activity

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Adefovir works by blocking reverse transcriptase, an enzyme that is crucial for the hepatitis B virus (HBV) to reproduce in the body. It is approved for the treatment of chronic hepatitis B in adults with evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases (primarily ALT) or histologically active disease. Adefovir is a failed treatment for HIV due to the severity and frequency of kidney toxicity when dosed at 60 or 120mg. However, trials have found the 10mg dose of adefov ...

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Adefovir, Adefovir - History, Adefovir - Mechanism of action

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Moisturizers act on the most external of the skin layers, the so-called corneal stratum (stratum corneum, the anatomical term in Latin), which is largely formed by squamous cells or keratinocytes (an epithelial layer which is quite dynamic, i.e., it is being constantly shed and replaced by the growth of new cells coming from the deeper layers of the skin, therefore its name). Most, if not all, agents present in moisturizers are unable to penetrate ...

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Moisturizer, Moisturizer - Mechanism of action, Moisturizer - Composition, Moisturizer - Adverse effects, Moisturizer - Reference

Read more here: » Moisturizer: Encyclopedia II - Moisturizer - Mechanism of action

Digoxin binds to a site on the extracellular aspect of the α-subunit of the Na+/K+ ATPase pump in the membranes of heart cells (myocytes). This causes an increase in the level of sodium ions in the myocytes, which then leads to a rise in the level of calcium ions. The proposed mechanism is the following: inhibition of the Na+/K+ pump leads to increased Na+ levels, which in turn slows down the extrusion of Ca2+ via the Na+/Ca2+ exchange pump. Increased am ...

See also:

Digoxin, Digoxin - Actions, Digoxin - Mechanism of action, Digoxin - Clinical use, Digoxin - Side effects, Digoxin - Other, Digoxin - In the news

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Didanosine (ddI) is a nucleoside analogue of adenosine. It differs from other nucleoside analogues, because it does not have any of the regular bases, instead it has hypoxanthine attached to the sugar ring. Within the cell, ddI is, by cellular enzymes, phosphorylated to active metabolite of dideoxyadenosine triphosphate, ddATP. Like other anti-HIV nucleside analogs, it acts as a chain terminator by incorporation and inhibits viral rev ...

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Didanosine, Didanosine - History, Didanosine - Mechanism of action, Didanosine - Adverse affects

Read more here: » Didanosine: Encyclopedia II - Didanosine - Mechanism of action

See the article on statins for more details. Rosuvastatin is a competitive inhibitor of the enzyme HMG-CoA reductase, having a mechanism of action similar to other statins. ...

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Rosuvastatin, Rosuvastatin - Presentation, Rosuvastatin - Mechanism of action, Rosuvastatin - Indications and regulation, Rosuvastatin - Marketing and competition, Rosuvastatin - Marketing, Rosuvastatin - Debate & Criticisms, Rosuvastatin - Myopathy, Rosuvastatin - Renal Effects, Rosuvastatin - Comments Changing Beliefs

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Despite its similar name, it is not a calcineurin inhibitor like tacrolimus or cyclosporine. However, it has a similar suppressive effect on the immune system. Sirolimus inhibits the response to IL-2 and thereby blocks activation of T- and B-cells. In contrast, tacrolimus and cyclosporine inhibit the production of IL-2. The mode of action of sirolimus is that it binds to the cytosolic protein FK-binding protein 12 (FKBP12), in a similar way to tacrolimus. However, unlike the tacrolimus-FKBP12 complex which inhibits calcineurin ...

See also:

Sirolimus, Sirolimus - Mechanism of action, Sirolimus - Use in transplant, Sirolimus - Anti-proliferative effects

Read more here: » Sirolimus: Encyclopedia II - Sirolimus - Mechanism of action