3.2 Cardiac Function Flashcards
List the four phases of diastole in order
- Isovolumetric relaxation
- Rapid inflow
- Diastasis (diastole-stasis)
- Atrial contraction (top up)
List the three phases of systole in order
- Isovolumetric contraction
- Rapid ventricular ejection
- Reduced ventricular ejection
Draw a left ventricular volume loop
https://www.adinstruments.com/sites/default/files/wysiwyg-resources/images/PV%20Loop%20parameter%20schematic%20Adam%20Goodwill.png
What produces S1?
Atrioventricular valve closure
What produces S2?
Semilunar valve closure
When does the S3 sound occur (if it occurs)?
Ventricular filling
What can cause an S4 heart sound to be heard?
Vibration of ventricular wall during end-diastolic atrial contraction
Define preload
The tension applied to the left ventricle before it contracts; affected by end-diastolic volume
What happens to cardiac contractility if preload becomes too high?
Cardiac muscle is stretched too far, and it begins to produce less contractile force
Will maximum preload always result in highest stroke volume?
- No
- There is a point at which the contraction of ventricles will produce maximum force; beyond this, the force will decreased despite increased stretching of cardiac muscle
List the three roles of atria in the cardiac cycle
- Collecting blood
- Passively filling ventricles
- Actively filling ventricles during atrial systole
Which two factors can be used to quantify/conceptualise afterload?
- Aortic pressure
- Properties of arterial system
What is the effect of increased/decreased preload on stroke volume?
Increased Preload: Increased Stroke Volume
Decreased Preload: Decreased Stroke Volume
What is the effect of increased/decreased afterload on stroke volume?
Increased Afterload: Decreased Stroke Volume
Decreased Afterload: Decreased Stroke Volume
Describe the location and mechanism of the baroreceptor reflex
- Location: carotid bodies and aortic arch
- Feed back information to the cardiovascular centre in the medulla
- Modulate autonomic innervation to regulate BP (incl. changes to heart and vascular system)
Describe the function aortic stretch receptors in the heart in response to increased stroke volume
- Detect if stretch is too high (meaning ventricular filling has increased)
- Modulates increase in heart rate if necessary
Describe the role of mechanoreceptors and metaboreceptors in skeletal muscle on heart function
- Feed back information regarding metabolic status of muscle to the cardiovascular centre, modulating stroke volume and heart rate (e.g. during exercise)
List the main receptor types involved in extrinsic cardiovascular regulation
- Aortic stretch receptors in heart
- Baroreceptors in carotid bodies and aortic arch
- Metaboreceptors and mechanoreceptors in skeletal muscle
Why might stroke volume decrease as HR increases?
Less time is available for diastolic filling, and so stroke volume decreases
Describe the cardiovascular response to exercise. What happens to stroke volume as heart rate nears its maximum?
- Central command assists with a rapid
early rise in HR. - Muscle pump ↑ venous return, which
↑ central venous pressure, thus
engaging the Starling mechanism. - Matching of HR to the metabolic
demand achieved by afferent
feedback via muscle mechano- and
metaboreceptors. - At higher HR, stroke volume plateaus
and falls due to limited diastolic filling
time. - At peak exercise, cardiac output
plateaus as HR reaches its upper
limit.
Which two factors can be used to quantify/conceptualise afterload?
- Aortic pressure
- Properties of arterial system
