adrenergic

Examples of adrenergic in the following topics:

• Adrenergic Neurons and Receptors

  • Adrenergic receptors are molecules that bind catecholamines.
  • There are two main groups of adrenergic receptors, α and β, with several subtypes. α receptors have the subtypes α1 (a Gq coupled receptor) and α2 (a Gi coupled receptor).
  • Adrenaline or noradrenaline are receptor ligands to α1, α2, or β-adrenergic receptors (the pathway is shown in the following diagram).
  • α1-adrenergic receptors are members of the G protein-coupled receptor superfamily.
  • This schematic shows the mechanism of adrenergic receptors.

• Local Regulation of Blood Flow

  • Generally, norepinephrine and epinephrine (hormones secreted by sympathetic nerves and the adrenal gland medulla) are vasoconstrictive, acting on alpha-1-adrenergic receptors.
  • However, the arterioles of skeletal muscle, cardiac muscle, and the pulmonary circulation vasodilate in response to these hormones acting on beta-adrenergic receptors.

• Agonists, Antagonists, and Drugs

  • 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.
  • Beta blockers block the action of endogenous catecholamines—epinephrine (adrenaline) and norepinephrine (noradrenaline) in particular—on β-adrenergic receptors, part of the sympathetic nervous system that mediates the fight-or-flight response.

• Postganglionic Neurons

  • In the sympathetic division, most are adrenergic, meaning they use norepinephrine as their neurotransmitter.
  • In response to this stimulus, postganglionic neurons—with two important exceptions—release norepinephrine, which activates adrenergic receptors on the peripheral target tissues.

• Autonomic Nervous System (ANS)

  • Recently, a third subsystem of neurons has been identified referred to as "non-adrenergic and non-cholinergic" neurons (because they use nitric oxide as a neurotransmitter).

• Heart Circulation

  • This mechanism is due to beta-adrenergic receptors in the coronary arteries and helps enable the increased cardiac output associated with fight-or-flight responses.