Flashcards in Week 8: Cardiology Deck (51)
Purpose of His-Purkinje System and bundle branches
To coordinate contraction of left and right ventricles
Which vessels provide the major resistance in the vascular tree?
They have smooth muscle that is subject to autonomic control. Because they are small and arranged in series, a small alteration to radius makes a large (^4) difference for resistance.
3 main epicardial arteries
Right coronary artery
Left main coronary artery, which divides into the left anterior descending artery and the left circumflex artery.
Three functions of pericardium
1. Cardiac mechanics
2. Lubrication with cardiac motion
3. Barrier for limiting infections
3 main layers of heart
visceral pericardium - pericardial cavity - parietal pericardium
Composition of a sarcomere in cardiac muscle
thin filament (actin-troponin-tropomyosin) and thick filament (B myosin) with subtypes specific to cardiac muscle.
What is the mechanism of cardiac contraction at the cellular level?
calcium-induced calcium release (excitation-contraction coupling). This is unique to cardiac sarcomere.
What kind of valves are the aortic and pulmonary valves?
What two events delineate the beginning and end of systole?
AV valve closure and semilunar valve closure. I.e., S1-S2
Equation for cardiac output
CO = SV x HR
Equation for BP
BP = CO x SVR
Define stroke volume
The volume of blood ejected from the ventricle with each contraction
Define cardiac output
The volume of blood ejected from the ventricle per minute
Define vascular resistance
The resistance conferred by the vessels that must be overcome by ventricular contraction
What is the S1 sound?
Mitral valve and tricuspid valve closure
What is the S2 sound?
Pulmonary valve and aortic valve closure
An abnormal heart sound that, if present, occurs in diastole. Occurs when the ventricle is volume overloaded, whereby the rapid cessation of blood flow early in diastole (as the atrial and ventricular pressure equilibrate) results in an abnormal heart sound.
An abnormal heart sound that, if present, occurs late in diastole. Occurs in pressure overloaded ventricle, whereby the extra pressure and volume conferred by atrial contraction into a stiff ventricle results in an abnormal heart sound.
What is a murmur?
Increased turbulent flow.
What are the three increased flow states that may be associated with a murmur?
1. Increased flow through normal structures in the context of increased metabolic demand
2. Turbulent flow through narrow orifices (narrowed valve, regurgitation, septal defect)
3. Flow into a larger distal chamber (aortic aneurysm)
When does pulmonic stenosis cause a murmur
When does mitral stenosis cause a murmur
How can anemia cause a murmur?
Increased flow through normal structures.
when would aortic regurgitation make a murmur?
What pressure difference signals the aortic valve to open?
When the LV pressure exceeds the aortic pressure
what is the ejection fraction?
Used to assess systolic function.
= SV / LV end-diastolic volume
Three determinants of stroke volume?
the ventricular wall tension developed at the end of diastole. Closely approximates LVEDV (left ventricular end diastolic volume)
the ventricular wall stress encountered during contraction (systole) that must be overcome in order to eject blood.