Cardio I Exam Flashcards
What causes the first heart sound (S1)?
Closure of the AV valves
What causes the second heart sound (S2)?
Closure of the semilunar valves
Where are B1 receptors found?
Mostly in the heart, specifically the conduction system (AV and SA nodes, Purkinje fibers) and the atrial and ventricular myocardium
What happens when B1 receptors of the heart are stimulated?
Stimulation increases heart rate (chronotropy) and force of myocardial contraction (inotropy)
Where are B2 receptors found?
Heart and vascular smooth muscle
What happens when B2 receptors are stimulated?
Stimulation increases heart rate and force of myocardial contraction. Also results in vasodilation because of the location of the receptors on vascular smooth muscle
Where are B3 receptors found?
In the myocardium and coronary vessels
What happens when B3 receptors are stimulated?
Stimulation opposes the effects of B1 and B2 receptor stimulation and decreases myocardial contractility (negative inotropic effect); may provide a “safety mechanism” to prevent overstimulation
Where are A1 receptors located?
Postsynaptic neurons in the systemic and coronary arteries
What happens when A1 receptors are stimulated?
Smooth muscle contraction and thus vasoconstriction
Where are A2 receptors located?
On the sympathetic ganglia and nerve terminals
What happens when A2 receptors are stimulated?
The effect of NE on these receptors is to inhibit release of more NE, which promotes vasodilation, thus providing another safety mechanism to prevent excess blood pressure elevation
Which vessels empty into the right atrium?
SVC, IVC, and coronary sinus
Which vessels empty into the left atrium?
Pulmonary veins
What is myocardial oxygen consumption (MVO2)?
Cardiac work, i.e., how much energy is used
What 3 major factors determine MVO2?
- Amount of wall stress during systole - estimated by measuring systolic BP
- Duration of systolic wall tension - measured indirectly by HR
- Contractile state of the myocardium - not measured clinically
Increased energy needs can be met ONLY by increasing _____________?
Coronary blood flow
What is the percentage of blood pumped out of the ventricles compared to the amount of blood in the ventricles at the end of diastole called?
Ejection fraction
What 4 factors affect cardiac output directly?
Preload, afterload, myocardial contractility, and heart rate
Volume inside the ventricle at the end of diastole is called
Preload
What is measured to estimate preload?
Central venous pressure (CVP) on the right side. Pulmonary artery wedge pressure on the left side.
What is the resistance to ejection of blood from the left ventricle?
Left ventricular afterload
An index of afterload is ___________
aortic systolic pressure
