Adrenergic antagonists: Beta blockers
28,832views

00:00 / 00:00
Questions
USMLE® Step 1 style questions USMLE
0 of 5 complete
USMLE® Step 2 style questions USMLE
0 of 9 complete
Memory Anchors and Partner Content
Transcript
Content Reviewers
Alpha blockers and beta blockers are two types of postsynaptic anti-adrenergic medications that prevent their respective receptors from being stimulated by catecholamines, like norepinephrine and epinephrine.
The nervous system is divided into the central nervous system, so the brain and spinal cord; and the peripheral nervous system, which includes all the nerves that connect the central nervous system to the muscles and organs. The peripheral nervous system can be 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. These two catecholamines activate the adrenergic receptors on many different organs, which allows the sympathetic nervous system to trigger the fight or flight response that increases the heart rate and blood pressure, as well as slowing down digestion. This response maximizes blood flow to the muscles and brain, and can help you either run away from a threat, or fight it, which is why it’s also called the fight or flight response.
Summary
Adrenergic antagonists are a type of drug that blocks the action of adrenaline in the body. Adrenaline is a hormone that is released in response to stress or excitement, and it causes the heart rate to speed up and the blood vessels to narrow.
Beta-blockers are a type of adrenergic antagonist that blocks the sympathetic activation of Beta-adrenergic receptors. Beta-blockers work by blocking the action of adrenaline, which is responsible for the body's fight-or-flight response. This makes them ideal for treating conditions where the body's natural response to stress is harmful, such as high blood pressure and heart arrhythmia.
Sources
- "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
- "Rang and Dale's Pharmacology" Elsevier (2019)
- "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
- "Chronotropic incompetence, beta-blockers, and functional capacity in advanced congestive heart failure: Time to pace?" European Journal of Heart Failure (2008)
- "Beta-blockers for hypertension" Cochrane Database of Systematic Reviews (2017)
- "Blood pressure lowering efficacy of beta-1 selective beta blockers for primary hypertension" Cochrane Database of Systematic Reviews (2016)
- "Treatment of Angina: Where Are We?" Cardiology (2018)
- "Bisoprolol compared with carvedilol and metoprolol succinate in the treatment of patients with chronic heart failure" Clinical Research in Cardiology (2017)
- "A Review of Nebivolol Pharmacology and Clinical Evidence" Drugs (2015)
- "Management of arrhythmia in sepsis and septic shock" Anaesthesiol Intensive Ther (2017)