BETA RECEPTORS

Question 1

How do B1 receptors work?

Answer 1

Couple to Gas (stimulatory)
Activates adenylyl cyclase and
increases cAMP conc
activation of PKA.

Question 2

Where are B1 receptors found?

Answer 2

SA node
AV node
Cardiac myocytes
Kidneys 
Vasomotor centre
Adipocytes

Question 3

What effect does activation of B1 receptors in SA node have?

Answer 3

Increase in heart rate

Question 4

What effect does activation of B1 receptors in cardiac myocytes have?

Answer 4

Increase in force of contraction

Question 5

What effect does activation of B1 receptors in AV node have?

Answer 5

Decrease in refractory period between APs so increase in heart rate as a result

Question 6

What is the overall effect of activation of B1 receptors?

Answer 6

Increase in HR and therefore an increase in SV and increase in CO which has a profound effect on BP

Question 7

Where in particular in the kidneys are B1 receptors expressed?

Answer 7

Juxtaglomerula apparatus

Question 8

B1 receptors in juxtaglomerula apparatus control the release of ______

Answer 8

renin

Question 9

Renin controls the conversion of?

Answer 9

Angiotensin I to angiotensin II

Question 10

Angiotensin II is a powerful vasodilator. True or false?

Answer 10

False - vasoconstrictor and therefore increases peripheral resistance and increases BP

Question 11

Angiotensin regulates secretion of which two things?

Answer 11

Aldosterone and ADH

Question 12

What is the role of aldosterone?

Answer 12

Na+ reabsorption into kidneys and K+ secretion therefore creating osmotic gradient for water to be reabsorbed into blood

Question 13

What is the role of ADH?

Answer 13

Prevents loss of water from urine

Question 14

What is the net effect of activation of B1 receptors in kidneys?

Answer 14

Increase in blood volume and so an increase in BP

Question 15

B1 receptors and B2 receptors function in the same way. True or false?

Answer 15

True

Question 16

How do B2 receptors work?

Answer 16

Couple to Gas
Stimulates adenylyl cyclase
increase concentration of cAMP
Activation of PKA

Question 17

Where are B2 receptors expressed?

Answer 17

Bronchial smooth muscle

Endothelial cells of specific blood vessels within skeletal muscle

Question 18

B2 receptors control bronchodilation. True or false?

Answer 18

True

Question 19

Which receptor controls production of NO and how does it do this?

Answer 19

B2 - present in endothelial cells of specific blood vessels within skeletal muscle and control the production of NO - vasodilator

Question 20

Why doesn’t activation of B2 receptors on blood vessels within skeletal muscle have much of an effect on BP?

Answer 20

Because although production of NO leads to vasodilation, there are a1 receptors present on vascular smooth muscle cells - vasoconstriction

Question 21

On activation of B2 receptors on blood vessels within skeletal muscle, blood flow is diverted away from skeletal muscle. True or false?

Answer 21

False - diverted towards skeletal muscle

Question 22

What is a side effect of drugs that act on B2 receptors?

Answer 22

Muscle tremor

Question 23

Activation of which receptor can lead to glycogenolysis in the liver and skeletal muscle?

Answer 23

B2 receptors

Question 24

B2 antagonists are used as bronchodilators. True or false?

Answer 24

False - B2 agonists

Question 25

Name two short acting B2-selective agonists that are used as bronchodilators

Answer 25

Salbutamol | Terbutaline

Question 26

Name two long active B2-selective agonists that are used as bronchodilators

Answer 26

Salmeterol | Eformoterol

Question 27

Why is tachycardia a side effect of B2 agonist bronchodilators?

Answer 27

Due to activation of cardiac B receptors which cause increase in HR

Question 28

Hypokalaemia is a side effect of B2 agonist bronchodilators. Why?

Answer 28

loss of potassium due to activation of Na+/K+ pump in skeletal muscle

Question 29

How are side effects of B2 agonist bronchodilators minimised?

Answer 29

By inhalation of drugs rather than oral administration

Question 30

Propranolol is a non-competitive antagonist. True or false?

Answer 30

False - competitive

Question 31

Is atenolol a selective or non-selective antagonist?

Answer 31

Selective B1

Question 32

Why does propranolol have a better CNS penetration than atenolol?

Answer 32

Because it is more lipid soluble, whereas atenolol is relatively water soluble

Question 33

What is the equation for BP?

Answer 33

BP = CO x PR

Question 34

Why does tachycardia decrease coronary perfusion?

Answer 34

Because there is less time to perfuse the heart

Question 35

How are B1 antagonists used in treatment of angina?

Answer 35

By blocking B1 receptors, there is a decrease in HR and so diastole is prolonged, which increases coronary blood flow and oxygen delivery

Question 36

B-antagonists can be used in treatment of pheochromocytoma. True or false?

Answer 36

True - used for cardio-protection alongside phentolamine and phenoxybenzamine

Question 37

Fastest AP is in AVN. True or false?

Answer 37

False - SAN

Question 38

How can B-antagonists be used to correct dysrhythmias?

Answer 38

reduce HR and prevent ectopic foci from occurring within muscle cells - restoring sinus rhythm

Question 39

Vivid dreams are a side effect of propranolol but not atenolol. True or false?

Answer 39

True

Question 40

Why does increased sensitivity to catecholamines lead to dysrhythmias?

Answer 40

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

Question 41

B-blockers are used to control symptoms in thyrotoxicosis. True or false?

Answer 41

True

Question 42

B-blockers can be used in treatment of chronic simple glaucoma by reducing aq humor. True or false?

Answer 42

True