Patient: Beta Adrenoceptors Flashcards Preview

Pharmacy Year 2 Semester 1 > Patient: Beta Adrenoceptors > Flashcards

Flashcards in Patient: Beta Adrenoceptors Deck (18):

Describe the binding when beta1 and beta2 adrenoceptors are activated

Galphas activates adenylyl cyclase
Increase in cAMP
increase in PKA (protein kinase A)


Describe the functional response when a beta1 adrenoceptor is activated

1) Heart: SA node, AV node, Myocardium
Increase HR
Decrease refractory period
Increase force of contraction

2) Juxtaglomerula cells - release of renin
3) GI smooth muscle relaxtion


Describe the functional response when a beta2 adrenoceptor is activated

1) Bronchodilation
2) Vasodilation
3) GI smooth muscle relaxation
4) Relaxation of visceral smooth muscle
5) Decrease in histamine release
6) Muscle Tremor
7) Glycogenolysis


Beta2 adrenoceptor activation: vasodilations effects?

-skeletal muscle vasculature
-release of Nitric Oxide (NO)


beta2 adrenoceptor activation: Relaxation of visceral smooth muscle effects?

-Bladder detrusor
-ciliary muscle
-seminal tract
-uterus (premature labour)


beta2 adrenoceptor activation: Glycogenolysis occurs where?

Hepatocytes and skeletal muscle


Functional response of beta3 adrenoceptors

Lipolysis (breakdown of fat) on adipocytes


Name beta2-selective agonists used as bronchodilator agents

Short acting (2-4 hours)
Salbutamol and terbutaline

Long acting (up to 12 hours)
Salmeterol and efortmoterol


Unwanted effects of beta-agonist bronchodilators

1) Tremor - peripheral effect involving interference with muscle spindle function
2) Tachycardia - activation of cardiac beta-AR
3) Nervous tension - effect on CNS
4) Hypokalaemia - stimulation of Na+/K+ ATPase in skeletal muscle


How are unwanted effects of beta-agonist bronchodilators reduced?

inhalational rather than oral administration


Name another use of a b-adrenoceptor agonist apart from bronchodilators

Supression of premature labour (tocolysis)
e.g. salbutamol or ritodrine
which are both beta2-selective agonists


Give 3 properties of Propranolol

-competitive agonist
-Non-selective Beta-adrenoceptor antagonist
-Relatively lipid soluble (good penetration of CNS)


Give 3 properties of Atenolol

-Competitive antagonist
-relatively selective beta1-adrenoceptor anatagonist
-relatively water soluble (poor penetration of CNS)


Give a use of beta-adrenoceptor antagonist
How does it work?

Anti-hypertensive drugs
Decrease in: cardiac output, renin release and sympathetic tone (vasomotor centre in medulla oblongata)


What is angina pectoris and how are beta-adrenoceptors used in its prophylaxis?

Angina of effort: crushing pain in chest that may radiate to arm, neck or jaw.
The pain results from cardiac ishaemia
Cardiac Beta1-AR blockade (propranolol)
-decreases cardiac rate, force and work
-prolongs diastole (bradycardia)
-increases coronary blood flow
-increases 02 delivery


How are B-AR antagonists used to control symptoms of thryotoxicosis

Thyroid hormone sensitises tissues to catecholamines (hence eyelid contraction occurs)
Symptoms that can be controlled by beta-blocker e.g. propanolol:
-Anxiety, tachycardia, Palpitations, tremor


Propanolol (beta-AR anatagonist) can be used for the prophylaxis of what other thing? (not cardiac)

Prophylaxis of migraine
Mechanism unclear but may involve anxiolysis (inhibits anxiety)


Unwanted effects of Beta-AR antagonists

1) Bronchoconstriction
-bronchial ashtma
2) Precipitation of cardiac failure/heart block
-patients with heart disease
-oxprenolol (partial agonist)
3) Hypoglycaemia
-patients with diabetes
-mask of sympathetic sweating, tachycardia and tremor
4) Cold extremities
-Raynaud's disease and claudication
5) vivid dreams
-propanolol (practolol)
-not a problem with atenolol