antagonist

Examples of antagonist in the following topics:

• Blocking of Hormone Receptors

  • Once bound, an antagonist will block agonist binding.
  • The term "non-competitive antagonism" (sometimes called non-surmountable antagonists) can be used to describe two distinct phenomena: one in which the antagonist binds to the active site of the receptor, and one in which the antagonist binds to an allosteric site of the receptor.
  • The second form of "non-competitive antagonists" act at an allosteric site.
  • Uncompetitive antagonists differ from non-competitive antagonists in that they require receptor activation by an agonist before they can bind to a separate allosteric binding site.
  • Many antagonists are reversible antagonists that, like most agonists, will bind and unbind a receptor at rates determined by receptor-ligand kinetics.

• How Skeletal Muscles Produce Movements

  • Muscles are arranged in groupings of agonist, antagonist, and synergists that produce and modulate movement.
  • The biceps and triceps muscle groups are an example of an agonist/antagonist pair.
  • During extension, the triceps act as the agonist while the biceps act as the antagonist.
  • The majority of muscles are grouped in pairs, with an antagonist to each agonist muscle.
  • The triceps brachii (not shown) acts as the antagonist.

• Agonists, Antagonists, and Drugs

  • Drugs acting on the acetylcholine system are either agonists to the receptors, stimulating the system, or antagonists, inhibiting it.
  • Agonists increase the level of receptor activation, antagonists reduce it.
  • Beta blockers (sometimes written as β-blockers) or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications.
  • As beta adrenergic receptor antagonists, they diminish the effects of epinephrine (adrenaline) and other stress hormones.
  • Distinguish between the effects of an agonist versus an antagonist in the autonomic nervous system

• Interactions of Hormones at Target Cells

  • Hormones that act to return body conditions to within acceptable limits from opposite extremes are called antagonistic hormones.
  • Hormones that act to return body conditions to within acceptable limits from opposite extremes are called antagonistic hormones.
  • The regulation of blood glucose concentration (through negative feedback) illustrates how the endocrine system maintains homeostasis by the action of antagonistic hormones.
  • These cells control blood glucose concentration by producing the antagonistic hormones insulin and glucagon.

• Divisions of the Autonomic Nervous System

  • This opposition is often viewed as complementary in nature rather than antagonistic.
  • More generally, these two systems should be seen as permanently modulating vital functions, in usually antagonistic fashion, to achieve homeostasis.

• Autonomic Interactions

  • However, this opposition is better termed complementary in nature rather than antagonistic.
  • More generally, these two systems should be seen as permanently modulating vital functions, in usually antagonistic fashion, to achieve homeostasis.

• Overview of the Parathyroid Glands

  • PTH has effects antagonistic to those of calcitonin by increasing blood calcium levels by stimulating osteoclasts to break down bone and release calcium.

• Parasympathetic Responses

  • This natural opposition is better understood as complementary in nature rather than antagonistic.

• Diuretics

  • The term "potassium-sparing" refers to an effect rather than a mechanism or location; nonetheless, the term almost always refers to two specific classes that have their effect at similar locations: Aldosterone antagonists: spironolactone, which is a competitive antagonist of aldosterone.

• Asthma

  • Leukotriene antagonists are less effective than corticosteroids and thus less preferred.
  • If mild persistent disease is present (more than two attacks a week), low-dose inhaled glucocorticoids or alternatively, an oral leukotriene antagonist or a mast cell stabilizer is recommended.