adrenaline

Examples of adrenaline in the following topics:

• Adrenal Medulla

  • The adrenal medulla secretes approximately 20% noradrenaline (norepinephrine) and 80% adrenaline (epinephrine).
  • When stimulated, chromaffin cells secrete adrenaline and noradrenaline along with enkephalin and enkephalin-containing peptides into the bloodstream.
  • The secreted adrenaline and noradrenaline play an important role in the fight-or-flight response.

• Overview of the Adrenal Glands

  • Along with catecholamines (adrenaline), these hormones control a variety of functions including kidney function, metabolism, fight-or-flight response, and sex hormone levels.
  • The cortex mainly produces mineralcorticoids, glucocorticoids, and androgens, while the medulla chiefly produces adrenaline and nor-adrenaline.

• Adrenergic Neurons and Receptors

  • The adrenergic receptors (or adrenoceptors) are a class of metabotropic G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine or noradrenaline, and epinephrine (adrenaline).
  • Adrenaline or noradrenaline are receptor ligands to α1, α2, or β-adrenergic receptors (the pathway is shown in the following diagram).
  • Adrenaline (epinephrine) reacts with both α- and β-adrenoceptors, causing vasoconstriction and vasodilation, respectively.
  • Adrenaline and noradrenaline are ligands to α1, α2, or β-adrenergic receptors. α1-receptors couple to Gq, resulting in increased intracellular Ca2+ and causing smooth muscle contraction. α2 receptors couple to Gi, causing a decrease in cAMP activity and resulting in smooth muscle contraction. β-receptors couple to Gs, increasing intracellular cAMP activity and resulting in heart muscle contraction, smooth muscle relaxation, and glycogenolysis.

• The Fight-or-Flight Response

  • The fight-or-flight response is regulated by the release of adrenaline or noradrenaline.
  • Simultaneously, the adrenal gland also releases catecholamine hormones, such as adrenaline or noradrenaline, into the blood stream.

• The Stress Response

  • This response is also referred to as the sympatho-adrenal response of the body owing to the fact that the preganglionic sympathetic fibers that end in the adrenal medulla secrete acetylcholine, which activates the release of adrenaline and noradrenaline from the medulla.
  • This response acts primarily on the cardiovascular system and is mediated directly via impulses transmitted through the sympathetic nervous system and indirectly via catecholamines, such as the adrenaline secreted from the adrenal medulla.

• Exhaustion

  • During this stage, adrenaline will be produced in order to bring about the fight-or-flight response.

• Glandular Epithelia

  • Examples of endocrine glands include the adrenal glands, located atop the kidneys and responsible for the secretion of certain hormones such as adrenaline, cortisol, and others.

• Excretion and Absorption

  • The stimulus for the secretion of apocrine sweat glands is adrenaline, which is a hormone carried in the blood.

• Sympathetic Nervous System

  • This secretion activates the secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine) from the adrenal medulla.

• Sympathetic Responses

  • This occurs as the preganglionic sympathetic fibers that end in the adrenal medulla secrete acetylcholine, which activates the secretion of adrenaline (epinephrine), and to a lesser extent noradrenaline (norepinephrine).
  • Catecholamine hormones, such as adrenaline or noradrenaline, facilitate the immediate physical reactions associated with a preparation for violent muscular action.