Cardiovascular Physiology 17 Flashcards
What two parts can the Cardiac Cycle be divided into?
Systole and Diastole
What are Systole and Diastole defined by?
The ventricles
What is Systole?
Ventricular contraction and blood ejections
What is Diastole?
Ventricular relaxation and filling of the ventricles with blood
What is the Cardiac cycle bound by?
The beginning of one heartbeat to the beginning of the next
What is the length of the cardiac cycle?
800 msec
What is the length of Systole and Diastole?
Systole: 300 msec
Diastole: 500 msec
What are the two phases that Ventricular Systole can be divided into?
- Isovolumetric ventricular contraction
* Ventricular ejection
What is the state of the heart valves during Isovolumetric Ventricular Contraction?
All heart valves are closed
What occurs during Isovolumetric Ventricular Contraction during Systole?
All heart valves are closed, the blood volume remains constant, pressure rise and the muscle develops tension but cannot shorten
What occurs during the Ventricular Ejection phase of systole?
Pressure in the ventricles exceeds that in arteries, semilunar valves open and blood is ejected into the artery. Muscle fibers of the ventricles shorten
Which valves open during Ventricular Ejection?
Semilunar valves to the Pulmonary artery and the Aorta
What keeps the AV valves closed during ventricular ejection?
The chordae tendineae and the papillary muscles
What is Stroke Volume?
The volume of blood ejected from each ventricle during systole
What is the difference between the ventricles during systole?
When the left ventricle contracts it contract with more force
Why doesn’t the heart eject its entire volume of blood during contraction?
In order to allow the heart to change the volume of blood that it pumps out depending on the body’s needs
What are the two phases of Ventricular Diastole?
- Isovolumetric ventricular relaxation
* Ventricular filling
Which valves close during Diastole?
The Semilunar valves
What is the state of the heart valves during Isometric Ventricular Relaxation during Diastole?
Both the AV and Semilunar valves are closed
What occurs during Isovolumetric Ventricular Relaxation?
All heart valves close, blood volume remains constant and pressures drop
What causes Ventricular Filling?
The pressure in the atria filling with blood that exceeds the pressure in the ventricles
What occurs during Ventricular Filling of Diastole?
AV valves open, blood flows into ventricles from atria. Ventricles receive blood passively
What is the state of the valves during Ventricular Filling?
AV valves are open and Semilunar valves are closed
What is the contraction state of both the atria and the ventricles during passive ventricular filling?
Both the atria and ventricles are relaxed
What completes ventricular filling?
The contraction of the atria
What is Atrial Kick?
Atria contraction at the end of ventricular filling
What valves must be open and close in order for the ventricles to receive blood from the atrium?
The AV valves must be open and the semilunar valves must be closed
What occurs in Atrial Systole?
The atrial contraction forces the last amount of blood into the relaxed ventricle, completing ventricular filling
What happens after Atrial Kick?
The atria remain in Diastole for the remainder of the cardiac cycle
What occurs after Atrial Systole is finished?
The ventricles enter systole
What closes the AV valves?
The pressure gradient created when the ventricular valves contract
What occurs during Isovolumetric contraction?
The heart contracts but does not create enough pressure to open the semilunar valves
What stage occurs after Isovolumetric contraction?
Ejection
What occurs in Ejection?
The ventricles contract hard enough to cause enough pressure to open the semilunar valves and blood is ejected into the arteries
What keeps the AV valves closed during Ejection?
Chordae Tendineae and the Papillary muscles
What occurs after the ejection phase?
The ventricles enter Diastole
What closes the semilunar valves during Diastole?
The blood flowing back closes them
What stage occurs after Ventricular Systole Ejection?
Isovolumetric Relaxation of ventricular Diastole
When does Passive Ventricular Filling occur?
After Isovolumetric relaxation where blood flows from the atria into the ventricles
What occurs after Isovolumetric Relaxation?
Passive Ventricular filling
