L2- Cardiovascular system design Flashcards
Requirements for efficient ventricular pumping
- Contractions of individual cardiac cells must occur at regular intervals and be synchronized (not arrhythmic)
- Valves must be fully open (not stenotic)
- Valves must not leak (not insufficient or regurgitant)
- Muscle contractions must be forceful (not failing)
- Ventricles must fill adequately during diastole
Relationship between cardiac output and oxygen consumption
Linear
Cardiac output definition
Quantity of blood per unit time pumped into the aorta by the heart
(CO=SVxHR)
Typical CO is 5 L/min
Major determinants of stroke volume
- Ventricular preload (length of muscle at onset of contraction
- Ventricular afterload (tension of muscle during contraction)
- Myocardial contractility
Starling’s law of the heart
Stroke volume increases as end-diastole volume increases. Primary regulator of cardiac output.
Stroke volume
Volume of blood ejected from ventricle in a beat
Cross sectional area changes of vessels throughout the body
Cross sectional areas increase as you distribute blood throughout the body and then begin to collapse back down as blood returns to the heart
Mean arterial pressure
Average pressure over the entire cardiac cycle. Estimated from diastolic pressure and pulse pressure. MAP=DP+1/3(SP-DP)=DP+1/3PP
Pulse pressure
The difference between the systolic and diastolic pressures PP=SP-DP
Systolic pressure
Peak arterial pressure reached during the ejection of blood by the heart
Diastolic pressure
Lowest arterial pressure reached when the heart is relaxed and filling with blood
Dichrotic notch (incisura)
Small dip caused by the backfilling of the aortic valve as it closes
Location of largest drop of MAP
Arteriolar segment of the circulation–site of highest vascular resistance
Short term control of MAP
Altering peripheral resistance counteracts moment-to-moment fluctuations of MAP–baroreceptors, vasomotor activity
Long term control of MAP
Achieved primarily by altering blood volume via the kidneys
