BETA RECEPTORS Flashcards
How do B1 receptors work?
Couple to Gas (stimulatory)
Activates adenylyl cyclase and
increases cAMP conc
activation of PKA.
Where are B1 receptors found?
SA node AV node Cardiac myocytes Kidneys Vasomotor centre Adipocytes
What effect does activation of B1 receptors in SA node have?
Increase in heart rate
What effect does activation of B1 receptors in cardiac myocytes have?
Increase in force of contraction
What effect does activation of B1 receptors in AV node have?
Decrease in refractory period between APs so increase in heart rate as a result
What is the overall effect of activation of B1 receptors?
Increase in HR and therefore an increase in SV and increase in CO which has a profound effect on BP
Where in particular in the kidneys are B1 receptors expressed?
Juxtaglomerula apparatus
B1 receptors in juxtaglomerula apparatus control the release of ______
renin
Renin controls the conversion of?
Angiotensin I to angiotensin II
Angiotensin II is a powerful vasodilator. True or false?
False - vasoconstrictor and therefore increases peripheral resistance and increases BP
Angiotensin regulates secretion of which two things?
Aldosterone and ADH
What is the role of aldosterone?
Na+ reabsorption into kidneys and K+ secretion therefore creating osmotic gradient for water to be reabsorbed into blood
What is the role of ADH?
Prevents loss of water from urine
What is the net effect of activation of B1 receptors in kidneys?
Increase in blood volume and so an increase in BP
B1 receptors and B2 receptors function in the same way. True or false?
True
How do B2 receptors work?
Couple to Gas
Stimulates adenylyl cyclase
increase concentration of cAMP
Activation of PKA
Where are B2 receptors expressed?
Bronchial smooth muscle
Endothelial cells of specific blood vessels within skeletal muscle
B2 receptors control bronchodilation. True or false?
True
Which receptor controls production of NO and how does it do this?
B2 - present in endothelial cells of specific blood vessels within skeletal muscle and control the production of NO - vasodilator
Why doesn’t activation of B2 receptors on blood vessels within skeletal muscle have much of an effect on BP?
Because although production of NO leads to vasodilation, there are a1 receptors present on vascular smooth muscle cells - vasoconstriction
On activation of B2 receptors on blood vessels within skeletal muscle, blood flow is diverted away from skeletal muscle. True or false?
False - diverted towards skeletal muscle
What is a side effect of drugs that act on B2 receptors?
Muscle tremor
Activation of which receptor can lead to glycogenolysis in the liver and skeletal muscle?
B2 receptors
B2 antagonists are used as bronchodilators. True or false?
False - B2 agonists
Name two short acting B2-selective agonists that are used as bronchodilators
Salbutamol
Terbutaline
Name two long active B2-selective agonists that are used as bronchodilators
Salmeterol
Eformoterol
Why is tachycardia a side effect of B2 agonist bronchodilators?
Due to activation of cardiac B receptors which cause increase in HR
Hypokalaemia is a side effect of B2 agonist bronchodilators. Why?
loss of potassium due to activation of Na+/K+ pump in skeletal muscle
How are side effects of B2 agonist bronchodilators minimised?
By inhalation of drugs rather than oral administration
Propranolol is a non-competitive antagonist. True or false?
False - competitive
Is atenolol a selective or non-selective antagonist?
Selective B1
Why does propranolol have a better CNS penetration than atenolol?
Because it is more lipid soluble, whereas atenolol is relatively water soluble
What is the equation for BP?
BP = CO x PR
Why does tachycardia decrease coronary perfusion?
Because there is less time to perfuse the heart
How are B1 antagonists used in treatment of angina?
By blocking B1 receptors, there is a decrease in HR and so diastole is prolonged, which increases coronary blood flow and oxygen delivery
B-antagonists can be used in treatment of pheochromocytoma. True or false?
True - used for cardio-protection alongside phentolamine and phenoxybenzamine
Fastest AP is in AVN. True or false?
False - SAN
How can B-antagonists be used to correct dysrhythmias?
reduce HR and prevent ectopic foci from occurring within muscle cells - restoring sinus rhythm
Vivid dreams are a side effect of propranolol but not atenolol. True or false?
True
Why does increased sensitivity to catecholamines lead to dysrhythmias?
Because pacemaker potential is activated, caused by inward movement of ca2+. This causes non-pacemaker cells to create AP separate from SAN leading to ectopic foci
B-blockers are used to control symptoms in thyrotoxicosis. True or false?
True
B-blockers can be used in treatment of chronic simple glaucoma by reducing aq humor. True or false?
True
