00:00 / 00:00
Adrenergic antagonists: Alpha blockers
Adrenergic antagonists: Beta blockers
Adrenergic antagonists: Presynaptic
Cholinomimetics: Direct agonists
Cholinomimetics: Indirect agonists (anticholinesterases)
Sympatholytics: Alpha-2 agonists
Sympathomimetics: Direct agonists
0 / 15 complete
0 / 7 complete
0 / 12 complete
Alpha-2 Agonists (Sympathoplegics)
as noradrenergic drug p. 238
norepinephrine and p. 238
serotonin-norepinephrine reuptake inhibitors (SNRIs) for p. 595
in noradrenergic drugs p. 238
norepinephrine for p. 241
norepinephrine vs p. 242
adrenal medulla secretion p. 330
amphetamines and p. 238
bupropion effect on p. 596
changes with disease p. 508
circadian rhythm p. 509
direct sympathomimetic p. 241
isoproterenol vs p. 242
male sexual response p. 647
MAO inhibitor effects p. 595
in nervous system p. 235
opioid effect on p. 569
phenoxybenzamine and p. 229
pheochromocytoma secretion p. 343
REM sleep and p. 509
tramadol effects p. 569
tyrosine catabolism p. 81
vitamin B6 and p. 65
norepinephrine and p. 229
Alpha agonists and beta agonists are two types of adrenergic medications that stimulate their respective receptors and mimic the effect of endogenous catecholamines, like norepinephrine and epinephrine.
The nervous system is divided into the central nervous system and the peripheral nervous system.
The peripheral nervous system can be further divided into the somatic nervous system, which controls voluntary movement of our skeletal muscles; and the autonomic nervous system, which controls the involuntary movement of the smooth muscles and glands of our organs; this system is then further divided into the sympathetic and parasympathetic nervous systems.
Now, the autonomic nervous system is made up of a relay that includes two neurons.
We’ll focus on just the sympathetic nervous system.
Signals for the autonomic nervous system start in the hypothalamus, at the base of the brain.
Hypothalamic neurons have really long axons that carry signals all the way down to the thoracic and lumbar spinal cord nuclei, where they synapse with preganglionic neuron cell bodies.
From there, the signal goes from the preganglionic neurons down its relatively short axon, exits the spinal cord, and reaches the nearby sympathetic ganglion, which is made up of lots of postganglionic neuron cell bodies.
The postganglionic neurons are also called adrenergic neurons, because they release the neurotransmitter norepinephrine, which is also called noradrenalin; and to a much lesser degree, epinephrine also known as adrenaline.
Sympathomimetics are drugs that act on the sympathetic nervous system to produce their effects. They include classes of drugs like alpha agonists and beta-agonists. Both alpha agonists and beta-agonists bind to receptors in the body and activate them.
Alpha agonists activate alpha receptors, which are found primarily in the smooth muscles of the blood vessels and lungs. Alpha agonists are divided into alpha-1 agonists, like phenylephrine and midodrine; and alpha-2 agonists, like clonidine. Phenylephrine is used to treat hypotension, but it can also be used as a decongestant to treat rhinitis, or as a topical agent to cause mydriasis. Midodrine is used to treat orthostatic hypotension; while intravenous and nasal administration of clonidine causes vasoconstriction.
On the other hand, beta-agonists activate beta receptors, which are found in the heart, lungs, and other organs. Beta-agonists are subdivided into non-selective beta agonists like isoproterenol; and selective beta-2 agonists, like albuterol, salmeterol, and terbutaline. Isoprenaline is used to stimulate the heart in individuals with bradycardia or heart block, while albuterol, salmeterol, and terbutaline are used in the treatment of asthma, chronic obstructive pulmonary disease, and hyperkalemia.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.