Regulation of Cardiac Function Flashcards
What happens during diastole in the heart?
Passive filling (from vena cava and pulmonary vein)
AV valves open
Pulmonary and aortic valves closed
Pressure is consistent between the atria and the ventricle
What happens to the heart during atria systole?
The AV valves are open
Aortic and pulmonary valves are shut
Last of the blood is ejected from the atria into the ventricles
What happens during isovolumetric contraction?
Both the AV and SL valves are closed.
No blood flow, isovolumetric contraction of the ventricles occurs during ventricular systole.
No change in ventricular volume but as the pressure begins to increase, the AV valves close.
Ventricular pressure increases dramatically.
What happens during ejection?
The AV valves and the SL valves are open. Rapid outflow of blood into the aorta and the pulmonary artery.
Ventricular pressure exceeds that of the aorta and pulmonary artery.
After a contraction, what happens in isovolumetric relaxation?
AV and SL valves shut. Ejection slows as ventricular contraction loses force. Brief backflow prevented by AV valve closing. One below the pressure of the outflow vessels, the aortic and pulmonary valves close to prevent backflow.
Ventricles undergo isovolumetric relaxation, rapidly decreasing pressure.
What is the time length for a cardiac cycle?
500msec
What causes the ventricles to mainly fill themselves once the mitral valve opens?
Elastic recoil of the ventricle
What is the dicrotic notch in the cardiac cycle caused by?
The aortic valve closing
What is the LVEDV?
What is LVESV?
What is the difference between them called?
Left ventricular end diastolic volume
Left ventricular end systolic volume
Stroke volume
What is the P wave?
What is the QRS complex?
What is the T wave?
P wave - atrial depolarisation
QRS - complex due to ventricular depolarisation
T wave - ventricular repolarisation
There are 4 sounds during heart contraction, lub-dub and 2 more noises. What are they due to?
S1 - initiation of V systole (lub sound)
S2 - closure of SL valves (dub sound)
S3 - opening of AV valves and rapid refilling
S4 - Atrial systole: rarely heard unless end diastolic pressure is raised
What is a murmur and what causes it?
It is a turbulence in the blood.
It is caused by increased blood velocity.
What is stenosis and what two murmurs does it cause?
It is the narrowing of blood vessels.
Mitral Stenosis - diastolic murmur as ventricle fills
Aortic stenosis - systolic murmur (high pressure)
What is valve incompetence and what two murmurs can it form?
It is leakage (backflow).
Mitral incompetence - a systolic murmur
Aortic incompetence - early diastolic murmur
What is a sign of valve incompetence and how do we test for it?
Pulsing veins (seen in the neck). A pulsating vein would stop pulsing if a patient sits up,. If it persists, then the pulsating may be in the carotid artery.
What is the main cause of valve incompetence and what is this disease caused by?
It is caused by endocarditis and this can occur due to a bacterial infection during dental procedures or gum disease.
What two things change stroke volume?
- Energy of contraction of the ventricles (filling pressure of right heart influencing diastolic stretch|)
- Resistance of outflow from the left ventricle
What is Frank - Starlings law?
Energy of contraction of the heart increases as a function of diastolic distention (stretching).
(Increased filling pressure increased ventricle pressure and contraction force)
What unit in the heart can increase in length to increase contractile force?
Sarcomere
What does the Frank - Starling ventricular function show?
Heart muscle increasing in stretch (an increase in end diastolic pressure) leads to an increase in stroke volume.
If the heart muscle becomes overstretched then the actin and myosin filaments have a very weak contractile force.
What does sympathetic stimulation do to the heart?
Increases contractility and heart rate.
If the stroke volume of the right heart increases, what happens to the left heart and why?
Increase in stroke volume because more blood more blood is returned to the left heart
What are the 7 stages of the cardiac cycle in order?
Atrial Systole Isovolumetric Contraction Rapid Ejection Reduced Ejection Isovolumetric Relaxation Rapid Ventricular Filling Slower Ventricular Filling
