Alpha and Beta Adrenergic Receptors

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Questions and Answers

What is the main action of β1 adrenergic receptors in the heart?

Stimulate increased heart rate and contraction (correct)

Inhibit heart rate and contraction

Cause vasodilation in coronary arteries

Promote glycogenolysis in the liver

Which effect is primarily associated with β2 adrenergic receptors?

Increased cardiac output

Vasodilation of skeletal and coronary blood vessels (correct)

Inhibition of insulin release

Decreased renin secretion

What classification of sympathomimetic drugs acts directly on adrenergic receptors?

Direct Acting (correct)

Dual (mixed) Acting

Indirect Acting

Non-selective Acting

What is the primary effect of epinephrine on cardiac function?

Positive chronotropic effect Signup and view all the answers

Which adrenergic receptor is associated with the relaxation of the urinary bladder?

β3 adrenergic receptor Signup and view all the answers

Which type of adrenergic receptor primarily inhibits the release of norepinephrine?

α1 adrenergic receptor Signup and view all the answers

What is a common adverse effect associated with the use of high doses of epinephrine?

Arrhythmias Signup and view all the answers

What happens to blood pressure when β2 adrenergic receptors are activated?

Blood pressure decreases due to vasodilation Signup and view all the answers

What is the main therapeutic use of isoprenaline?

Bradycardia due to heart block Signup and view all the answers

Which selective α1-agonist is a prodrug hydrolyzed to its active form?

Midodrine Signup and view all the answers

Which of the following is NOT a therapeutic use of selective β2-agonists?

Nasal decongestant Signup and view all the answers

What is a common adverse effect associated with the long-term systemic use of selective β2-agonists?

Hypokalemia and muscle cramps Signup and view all the answers

What characteristic of selective β2-agonists makes them advantageous over non-selective β agonists?

Reduced cardiac complications Signup and view all the answers

Which adverse effect is commonly associated with α1-agonists when used locally?

Rebound nasal congestion Signup and view all the answers

Which of the following is a direct effect of β1 receptor agonism?

Increased heart rate Signup and view all the answers

Fenoldopam is primarily used for which condition?

Severe hypertension Signup and view all the answers

What is the primary effect of alpha-1 adrenergic receptors in blood vessels?

Vasoconstriction Signup and view all the answers

Which of the following receptors are primarily involved in inhibiting sympathetic outflow and decreasing blood pressure?

Alpha-2 adrenergic receptors Signup and view all the answers

What is a common effect of beta-2 adrenergic receptor activation?

Bronchodilation Signup and view all the answers

Which of the following effects is characteristic of alpha-1 adrenergic receptor stimulation?

Constriction of urinary sphincters Signup and view all the answers

Which adrenergic receptor is primarily responsible for mediating lipolysis in fat cells?

Beta-2 adrenergic receptors Signup and view all the answers

What effect can excessive stimulation of beta-1 adrenergic receptors have on the heart?

Increased myocardial oxygen demand Signup and view all the answers

What is a common adverse effect associated with alpha-1 adrenergic receptor agonists?

Mydriasis Signup and view all the answers

Which adrenergic receptors are involved in both central and peripheral neurotransmission?

Dopaminergic receptors Signup and view all the answers

Study Notes

Alpha Adrenergic Receptors

Alpha-1 receptors are linked to Gq proteins and primarily located in smooth muscles.
Vasoconstriction occurs in blood vessels, leading to increased blood pressure.
Smooth muscle relaxation in the gastrointestinal tract and urinary bladder wall, while sphincters contract.
Active mydriasis results from the stimulation of dilator pupillae muscle in the eye.
Alpha-2 receptors, linked to Gi proteins, are primarily found in neuronal sites and inhibit various functions.
They decrease central sympathetic outflow, leading to reduced blood pressure and induce lipolysis.
Alpha-2 receptors inhibit insulin secretion and renin release, while promoting platelet aggregation and vasoconstriction.

Beta Adrenergic Receptors

Beta-1 receptors are linked to Gs proteins and are predominantly found in cardiac muscles.
Cardiac stimulation results in increased heart rate (HR), contraction strength, and conduction velocity, enhancing cardiac output and blood pressure.
Beta-1 receptors also influence lipolysis and stimulate renin secretion, which leads to angiotensin II production and vasoconstriction.
Beta-2 receptors, also linked to Gs proteins, mediate smooth muscle relaxation, primarily causing vasodilation in skeletal and coronary blood vessels.
Bronchodilation and mast cell stabilization are key effects of beta-2 activation, alongside weaker insulin release and glycogenolysis in the liver and muscles, raising blood glucose levels.
They also allow uterine and intestinal relaxation.
Beta-3 receptors are involved in lipolysis and relaxation of the detrusor muscle of the urinary bladder.

Dopaminergic Receptors

D1 receptors cause vasodilation in renal, coronary, cerebral, and mesenteric blood vessels.
D2 receptors, found presynaptically, decrease dopamine and norepinephrine release from nerve endings.

Sympathomimetic Drugs (Adrenergic Agonists)

Direct Acting: Act directly on adrenergic receptors.
Indirect Acting: Promote norepinephrine release or inhibit its reuptake.
Dual (Mixed) Acting: Combine both mechanisms.

Direct Acting Adrenergic Agonists

Epinephrine: A non-selective agonist affecting α1, α2, β1, and β2 receptors, increases force of contraction, heart rate, and conduction speed, and may cause arrhythmias at high doses.
Isoprenaline: A synthetic catecholamine acting on β1 and β2; increases cardiac output and induces bronchodilation and vasodilation.

Selective Alpha-1 Agonists

Phenylephrine: Long-acting and not inactivated by COMT; used for hypotensive states, mydriasis, decongestion, and hemorrhoid treatment.
Midodrine: A prodrug for postural hypotension with potential adverse effects like hypertension and bradycardia.

Selective Beta-Agonists

Dobutamine: β1 selective, enhancing heart performance without significant cardiac complications.
β2 Agonists:
- Used in bronchial asthma and preventing premature labor.
- Side effects include anxiety, muscle tremors, tachycardia, and potential for tolerance.

Selective D1 Agonist

Fenoldopam: Induces peripheral vasodilation, mainly used intravenously for severe hypertension.

Adrenergic Neurotransmitters

Norepinephrine: Functions primarily in postganglionic sympathetic fibers and select CNS tracts.
Epinephrine: Major hormone of the adrenal medulla.
Dopamine: Functions as both a central and peripheral neurotransmitter.

Overview of Sympathetic Nervous System

The sympathetic system is essential for regulating heart and peripheral vascular activities, especially during stress responses.
Adrenergic receptors belong to the G-protein family, facilitating various physiological responses in the body.

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Description

This quiz covers the functions and properties of alpha and beta adrenergic receptors, including their role in the inhibition of neurotransmitter release and cardiac stimulation. Test your understanding of how these receptors affect heart rate, contraction, and blood pressure regulation.