Events of the Cardiac Cycle Flashcards
General functions of the cardiovascular system
Heart - Pump that generates pressure gradient to move fluids
Blood Vessels - Passageways through which blood is distributed to different body parts
Blood - Transport medium for delivery of gases, nutrients and hormones
Events of the Cardiac Cycle
Cardiac Excitation
–>
(Pacemaker Cells [SA Node]; Conduction pathways [AV Node, Bundle of his, etc.])
–>
Excitation-Contraction coupling
–>
(Ventricular Myocyte Action Potential; Calcium influx)
–>
Cardiac Contraction
Describe blood flow along the heart
Compare the volume output of the LHS vs RHS of the heart with numbers
LHS = RHS
~5L/min
70ml/beat
Compare the pressure generated of the LHS vs RHS of the heart with numbers
LHS ~ 4 x RHS
~120 cf 30mmHg
Systole and Diastole
Systole - Contraction
Diastole - Relaxation
How does pressure affect fluid (blood) travel
Fluid flows from region of high to low pressure
How do valves affect the flow of blood with regard to pressure
Direction of flow is determined by unidirectional valves; they open/close due to pressure differences across them
Describe the pressure of the aorta, LV, LA as well as volume of LV during atrial systole
Short delay period is as a result of AV node
Describe the pressure of the aorta, LV, LA as well as volume of LV during isovolumetric ventricular contraction
Describe the pressure of the aorta, LV, LA as well as volume of LV during ventricular ejection
LV pressure exceeds Aortic pressure
Describe the pressure of the aorta, LV, LA as well as volume of LV during isovolumetric ventricular relaxation
(Check around 30 minutes into lecture)
Ventricular Filling
Describe the pressure of the aorta, LV, LA as well as volume of LV during ventricular filling
Compare the timings of an ECG and heart pressure
ECG spikings slightly precede contraction and changes in heart pressure
Jugular Venous Pulse
Pulsations in the internal jugular vein reflect right atrial pressure changes (no valves)
Describe the heart sounds and when they occur
1st - Low pitched ‘lub’ associated with AV Valve closure
2nd - Brief high pitched ‘dup’ associated with aortic/pulmonary valve closure
3rd - Vibration of ventricular wall when filling
4th - Associated with ventricular filling during atrial systole
Describe the sequence of Lub Dup sounds and systole/diastole
Stenosis
Narrowing of the heart vessels/valves; creates a steep pressure gradient causing turbulence across the valve (makes a sound)
Leaky/Incompetent/Insufficient Valve and associated sound
Flow can occur in different directions (regurgitation)
Murmur when valve should be closed
Causes of heart murmurs (abnormal heart sounds)
High Flow
Flow in different directions
