CVS physiology 2 Flashcards
Why is there a second dip in the QRS complex?
The upper part of the interventricular septum depolarises.
Why is the T wave positive?
As the wave of repolarisation is moving away from the left leg.
What is the comparison of size of the QRS complex for SLL I, SLL II and SLL III.
SLL II is biggest
SLL I is smallest
SLL III is in-between
What does the rhythm strip allow you to work out?
Heart rate
What is STEMI?
ST elevation myocardial infarction
What can be used to classify severity of MI on ECG?
STEMI or NSTEMI
What is the difference in end diastolic volume and end systolic volume equal to?
Stroke volume
What is ejection fraction?
Stroke volume / End diastolic volume
What is normal ejection fraction?
55-70%
What is pulse pressure?
Difference between systolic and diastolic pressure
What is the isometric contraction phase during cardiac cycle?
Increase in ventricular pressure, caused by contraction whilst valves are closed
What is the rapid ejection phase in the cardiac cycle?
Mass movement of blood out of the ventricle caused by the opening of the aortic valve.
What is the rapid filling phase in the cardiac cycle?
Mass movement of blood into the ventricle caused by opening of mitral valve.
What causes the dicrotic notch in the atrial pressure curve?
Closure of the aortic valve
What causes the wave in the atrial pressure curve?
Atrial contraction
What causes the C wave in the atrial pressure curve?
Inward bulge of mitral valve caused by ventricular contraction
What causes the v wave in the atrial pressure curve?
Filling of atrium whilst mitral valve is closed
What causes the “lub” sound of the heart?
Closing of mitral and tricuspid valves
What causes the “dub” sound of the heart?
Closing of aortic and pulmonary valves
What are the 3 types of murmur?
Systolic, diastolic, continuous
What impact does the sympathetic nervous system have on the heart?
- Release of noradrenaline acts on beta 1 receptors on the sinoatrial node
- Leading to an increase in the slope of the pacemaker potential
- Increasing heart rate
What impact does the parasympathetic nervous system have on the heart?
- Vagus nerve release ACh which acts on muscarinic receptors on sinoatrial node
- Then hyperpolarises cells and decreases slope of pacemaker potential - decreasing heart rate.
What does starlings law state?
The energy of contraction is proportion to the preload on the heart.
What is preload determined by?
End diastolic volume
What impact does increased total peripheral resistance have on stroke volume and why?
Decreases stroke volume
Because aortic pressure will increase, meaning the ventricle will have to work harder to open aortic valve leaving less energy to eject the blood
What effect does the sympathetic nervous system have on stroke volume?
Noradrenaline is released and acts on beta 1 receptors on myocytes, increasing contractility (stronger and shorter contraction)
What effect does the parasympathetic nervous system have on stroke volume?
Little effect
What are the 3 main factors that effect stroke volume?
Preload
Contractility
Afterload
What is heart rate x stroke volume equal to?
Cardiac output
What fraction of the cardiac cycle is systole?
1/3
What fraction of the cardiac cycle is diastole?
2/3
What factors can increase cardiac output?
HR increase
Contractility increase
Venous return increase
Total peripheral resistance increase
