Cardiovascular Flashcards
What effect do inotropes have on the heart?
Positive inotropes increase heart contractility
Negative inotropes decrease heart contractility
How do cardiac glycosides cause a positive inotropic effect? (increase strength of contractility)
Inhibit Na/K pump in myocytes meaning Na is retained (more intracellular Na). Reduced Ca extrusion from cell. Therefore more Ca moved into sarcoplasmic reticulum to be released during an action potential.
What effect do lusiotropes have on the heart?
Affect relaxation of ventricles
What effect do chronotropes have on the heart?
Affect heart rate
How do sympathomimetics increase heart contractility?
B1 receptor agonists on myocytes.
What are the 5 drug groups used as positive inotropes?
Sympathomimetics PDE III inhibitors Cardiac glycosides Glucagon Anticholinergics
How do PDE III inhibitors increase heart contractility?
PDE III degrades intracellular cAMP, so by inhibiting it we are increasing cAMP.
cAMP activates protein kinase A, which phosphorylates a site on the Ca channels, making them more likely to open, increased Ca into cell, stronger contraction.
Control of heart rate and rhythm is determined by which nervous system?
Autonomic
What are the 4 classes of antidysrrhythmics?
I= drugs which block sodium channels II= beta blockers III= drugs which prolong the action potential by blocking some K channels IV= drugs which block calcium channels
What are the effects of ACE inhibitors?
Vasodilation and reduced circulatory volume (hence reduced preload, increased tissue perfusion, reduced systemic arterial pressure)
What are the effects of the RAAS?
Aldosterone production which cause sodium and water retention, thus increasing blood volume
Causes vasoconstriction
What is the normal systolic BP of a dog?
140mmHg
