agonist

(noun)

These muscles are typically associates with the movement itself, and are sometimes referred to as prime movers. They contract while another muscle relaxes.

Related Terms

Examples of agonist in the following topics:

  • 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 biceps brachii is the agonist, or primer mover, responsible for flexing the forearm.

  • Blocking of Hormone Receptors

    • Agonists and antagonists "compete" for the same binding site on the receptor.
    • Once bound, an antagonist will block agonist binding.
    • High concentrations of a competitive agonist will increase the proportion of receptors that the agonist occupies.
    • They do not compete with agonists for binding at the active site.
    • This type of antagonism produces a kinetic profile in which "the same amount of antagonist blocks higher concentrations of agonist better than lower concentrations of agonist. "

  • Agonists, Antagonists, and Drugs

    • Agonists increase the level of receptor activation, antagonists reduce it.
    • They are ligand-gated ion channels with binding sites for acetylcholine as well as other agonists.
    • When agonists bind to a receptor it stabilizes the open state of the ion channel allowing influx of cations.
    • Most indirect acting ACh receptor agonists work by inhibiting the enzyme acetylcholinesterase.
    • Distinguish between the effects of an agonist versus an antagonist in the autonomic nervous system

  • Adrenergic Neurons and Receptors

    • Many cells possess these receptors, and the binding of an agonist will generally cause a sympathetic (or sympathomimetic) response (e.g. the fight-or-flight response).
    • Phenylephrine is a selective agonist of the α receptor. β receptors have the subtypes β1, β2 and β3.
    • Agonist binding thus causes a rise in the intracellular concentration of the second messenger cAMP.
    • Isoprenaline is a nonselective agonist.
    • relaxation of Bronchioles (salbutamol, a beta 2 agonist relieves bronchiole constriction).

  • Analgesia: Relief from Pain

    • Buprenorphine is thought to be a partial agonist of the opioid receptor, and tramadol is an opiate agonist with SNRI properties.

  • Components of a Reflex Arc

    • In the case of peripheral muscle reflexes (patellar reflex, achilles reflex), brief stimulation to the muscle spindle results in contraction of the agonist or effector muscle.

  • Proprioceptive Sensations

    • In a Golgi tendon reflex, skeletal muscle contraction causes the agonist muscle to simultaneously lengthen and relax.

  • Asthma

    • Treatment of acute symptoms is usually with an inhaled short-acting beta-2 agonist (such as salbutamol).

  • Cholinergic Neurons and Receptors

    • The result was also found in Alzheimer's disease patients and smokers after nicotine (an ACh agonist) consumption.