Lecture 6 Flashcards
Cardia Cycle
coordinated sequence of mechanical and electrical events that repeats with every heartbeat
Heart rate of 75 beats/min, how long do cardiac cycles
0.8 sec
Systole
1- Period of contraction and emptying
2- Atrial Systole and ventricular systole
Diastole
1- Period of relaxation and filling
2- Atrial diastole and ventricular diastole
Stroke Volume
1- Quantity of blood pumped out of either ventricle per beat
2- @ rest - 70 ml/beat; maximum -120 ml/beat
Heart Rate
1- # of times the heart beats per minute
2- @ rest - 72 beats/min; maximum - 230 beats/min
Cardiac Output
1- quantity of blood pumped by either ventricle per minute
2- @ rest - 5 L/min; maximum - 20-25 L/min
HR x SV = CO
Venous Return (VR)
1- Quantity of blood returned to the heart per minute
2- normally, venous return equals CO
End Diastolic Volume (EDV)
1- Quantity of blood remaining in either ventricle at the end of ventricular diastole
2- Average value is around 130 ml
End Systolic Volume (ESV)
Quantity of blood remaining in either ventricle at the end of ventricular systole
End of Isovolumetic ventricular relaxation
1- Left atrial pressure (LAP) exceeds left ventricular pressure (LVP), resulting in opening of the mitral valve
2- Ventricular filling ensues
Ventricular Filling (3 Phases)
1- Rapid Passive Filling
2- Slow Passive Filling (Diastasis)
3- Atrial Systole
Rapid Passive Filling
1- Blood flows quickly through the mitral valve and into the relaxed ventricle
2- ventricular volume increases
3- No muscle contraction occurs
4- 3rd heart sound produced
Slow passive filling
1- Blood flows slowly through the mitral valve and into the relaxed ventricle
2- Venticular volume continues to increase
3- No muscle contraction occurs
Atrial Systole
1- Left atrium must first be depolarized (note the location of the P wave just before atrial systole)
2- Atria contract
3- 4th heart sound produced
4- contribution of atrial contraction to ventricular filling is usually SMALL ( approx 10-15% of the total ventricular volume)
5- The left ventricle must first be depolarized ( note the location of the QRS complex just before IVC)
6- Ventricles contract and LVP pressure rises steadily, however no ejection of blood occurs as left ventricular volume remains constant
Rapid Ventricular Ejection
1- The Left ventricle develops enough pressure such that LVP exceeds aortic pressure
2- The aortic semilunar valve opens and blood is ejected; Aortic pressure rises
3- Left Ventricular pressure continues to rise also
Entering Back into Isovolumetric Relaxation
1- Once blood is ejected, LVP falls below aortic pressure and the aortic semilunar valve shuts
2- Second heart sound produced
3- Aortic pressure falls as blood runs off to arteries
4- T wave produced
5- The volume of blood remaining in the left ventricle after ejection is the ESV
Isovolumetric ventricular relaxation
1- All four chambers of the heart are relaxed and all of its valves are closed
2- Ventricular volume is constant
3- Ventricular pressure is decreasing
4- Left atrium is filling with blood that has returned to it via the pulmonary veins
5- Atrial pressure is rising
Dichrotic Notch
1- Closure of the aortic valve causes a brief rise in aortic pressure as back flowing blood rebounds off the closed valve cusps
2- The dichroic notch is significant in relation to coronary blood flow
