Beta blocker tutorial Flashcards
Name 4 organs/organ systems involved in blood pressure control.
Kidneys, Heart, Vasculature, Brain.
What are the effects of B1 receptor stimulation on the nodes and atrial cells.
Nodes - chronotropic effect.
Atria - ionotropic effect.
What receptors are responsible for VSMC contraction and dilation during exercise.
B2 - dilation in skeletal muscle.
A1 - constriction where not needed, e.g. digestive system.
(both NA).
Is constriction or dilation during exercise more responsible for rise in TPR?
Constriction since variation in viscera blood supply has a great effect on BP and TPR.
What stimulates renin secretion?
NA via B1 receptors at the kidney.
What are the effects of renin.
Stimulate AGT II secretion and aldosterone.
What are the effects of AGT II and aldosterone and why?
Aldosterone - increased BP due to increased blood volume (increased salt retention).
AGT II - increased BP due to vasoconstriction via AE1 receptor on blood vessels.
How is AGT II secreted?
Renin stimulates conversion of Angiotensinogen to AGT I in liver. ACE from lungs converts AGT I to AGT II.
What is the effect of beta blockers on hypertension.
Blocked B1 receptors on heart reduce cardiac output so reduce BP.
Blocked B1 receptors on kidneys reduce AGT II production (via renin-angiotensin system).
(no longer first line treatment).
How do beta blockers treat tachycardia?
Blocked B1 receptors on SA node reduce heart rate.
Name some common arrhythmias
Atrial flutter
Atrial fibrillation
Why are beta blockers used to treat arrhythmias?
Beta blockers have a negative dromotropic effect - reduce speed of conduction through the bundle of His
How does an atrial flutter arise?
HR generated by SA node = approx. 110-120, reduced by AV node to 60. In atrial flutter SA nodes overwhelms this.
What is a cardioselective beta blocker
Refers to drugs that are B1 selective.
What conditions are beta blockers contraindicated for?
Hypotension
Asthma
Diabetes.
why can beta blockers be problematic for asthmatic patient?
B receptors in airways cause bronchodilator. Blocking those can inhibit relaxation - net constriction effect.
Why can beta blockers be dangerous for diabetic patients?
Body fails to detect hypoglycaemic trough since SNS is inhibited by beta blockers. Body less likely to display the danger signals associated with hypoglycaemic troughs.
What is a crossover trial?
Each intervention is repeated in each group, with one variable being changed between groups.
