1. Cardiac Output – amount of blood pumped from the ventricles in one minute
Stroke Volume – amount of blood pumped from the heart in one ventricular
contraction
SV = EDV-ESV
End Diastolic Volume (EDV) – amount of blood in the ventricles at the end of
diastole/ before contraction
End Systolic Volume (ESV) – amount of blood in the ventricles at the end of
systole/ after contraction

2. 3 Factors That Influence Stroke Volume
Preload – degree to which cardiac muscle cells are stretched just before contraction (Frank-Starling Law of the Heart)
--intrinsic factor
--determined by EDV
--most important factor influencing EDV is venous return (slow heart rate, venoconstriction)
Contractility – contractile strength achieved at given muscle length
--extrinsic factor
--calcium = more cross bridging between myosin and actin
--sympathetic stimulation

3. Afterload -- back pressure of arterial blood that must be overcome for ventricules to eject blood
--extrinsic factor

4. Regulation of Heart Rate
Autonoic Nervous System
Sympathetic >
causes SA node to fire more rapidly because threshold is reached
more quickly
Parasympathetic >
slows heart rate because acetylcholine hyperpolarizes the
heart

5. Chemical Regulation
Hormones
-- epinephrine > enhances heart rate and contractility
--Thyroid Hormone >enhances epinephrine and norepinephrine effects
>alone provides slower, sustained increase in heart rate
Ions
--Ca 2+ deficiency in blood depresses heart
-- K +
-- excessive lowers resting potential (makes it more positive)
--deficiency cause heart to beat weakly and out of rhythm

6. Irregular Heart Rates Tachycardia – abnormally fast heart rate
-- more than 100 bpm
Causes – stress, certain drugs, heart disease
2) Bradycardia – slow heart rate
-- slower than 60 bpm
Causes – certain drugs, parasympathetic nervous activation,
endurance training