pump Flashcards
Cardiac Output (CO) is the
volume of blood pumped per minute by the heart (~5 L/min at rest)
CO =
HR x SR
cardiac output = heart rate x stroke volume
Stroke volume is the
amount of blood pumped per beat.
Representative numbers for “average” person at rest
HR ~ 70 beats/min
SV ~ 70 ml/beat
CO = HR x SV ~ 4.9 L/min
two ways to control cardiac output
- HR
2. SV
heart rate is set by
sinoatrial (SA) node
It is highly regulated by autonomic nervous system and humoral agents
Stroke volume is dependent on
- preload
- afterload
- strength of contraction
preload is the
venous return
afterload is the
resistance to flow (normally aortic pressure)
Strength of contraction
Length-dependent intrinsic regulation (Starling’s Law) and length-independent regulation via sympathetic nervous system
During diastole (filling phase), the mitral valve is
open
during systole, (contraction phase) the aortic valve is
closed
EDPVR stands for
end diastolic pressure volume relationship
EDPVR is the
Pressure-volume relationship during filling of heart BEFORE contraction
EDPVR corresponds to
passive elastic properties of ventricle (slope is inverse of compliance)
EDPVR slope is
shallow in normal physiological range (high compliance)
The EDPVR represents the
PRELOAD on the left ventricle
SPVR stands for
systolic pressure volume relationship
SVPR pressure-volume relationship at
peak of isometric contraction
SVPR represents the
Maximum pressure that can be developed for a given set of circumstances
SVPR curve is
Steeper than EDPVR – pressure increases a lot for small changes in volume
SVPR includes
active plus passive properties
preload is the
- volume entering the ventricles
2. The load/length to which a muscle is subjected before shortening.
afterload is the
- resistance that the left ventricle must overcome to circulate blood
- the load against which a muscle contracts
preload range
values lie along the diastolic pressure-volume curve.
preload for left ventricle
~ end diastolic volume.
afterload for the left ventricle is
~aortic pressure
afterload range
(without changes in contractility) lie along the systolic pressure-volume curve
Ventricular Function (Starling) curve
- Difference between SPVR and EDPVR
- Represents ACTIVE tension (i.e., that generated by contraction)
- Ascending & descending limbs
- Analogous to sarcomere length-tension curves
- Families of Starling curves for different inotropic states
- Multiple ways to plot (y-axis = pressure, tension, cardiac output, stroke volume; x-axis = volume or length)
Starling’s Law is an _____ property of the heart.
INTRINSIC
starling’s law is independent of
autonomic nervous system regulation
starling’s law is analogous to
and dependent on, the sarcomere length-tension relationship
