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By: Affan Malik
Physiology 1
Case Study
Cardiac output:
The amount of blood being pumped
by the heart, coming from the
ventricles into the aorta per minute.
Equation:
Cardiac output = stroke volume X cardiac rate
(ml/min)
(ml/beat)
(beats/min)
At 70 beats/min and 80 ml/beat, this results in
approximately 5.5 liters per minute
Cardiac Output:
Heart Rate X
Stroke Volume
Regulation of cardiac rate
Rhythm is set by the SA node
Sympathetic nerves
epinephrine and nonepinephrine
stimulate opening of calcium and sodium
channels; increase cardiac rate
Parasympathetic (vagus) nerves
acetylcholine promotes opening of potassium
channels; reduces cardiac rate
Exercise reduces vagus inhibition and
increases sympathetic nerve activity
The cardiac control center in the medulla
oblongata coordinates this activity
This in turn is regulated by higher brain activity
and pressure in aorta and carotid arteries
Regulation of stroke volume
End-Diastolic Volume (blood left in ventricles
after diastole)
increase in EDV increase in stroke volume
Total peripheral resistance to arterial blood flow
stroke volume is temporarily inversely proportio
to this
Contractility:
Innervation from sympathetic nerves
Raises calcium levels (positive inotropic effect)
Factors on Cardiac Output
1) Preload:
2) Afterload:
3) Contractility:
4) Heart Rate:
Factors on Cardiac Output
1) Preload:
 Preload 
 cardiac output
(Starling-Frank Mechanism)
Factors on Cardiac Output
More out
1) Preload:
 Preload 
 cardiac output
More in
(Starling-Frank Mechanism)
Factors on Cardiac Output
1) Preload:
2) Afterload:
 afterload   CO
R
Factors on Cardiac Output
1) Preload:
2) Afterload:
3) Contractility:
 contractility   CO
Factors on Cardiac Output
1) Preload:
2) Afterload:
3) Contractility:
4) Heart Rate:
Dual Effects
CO = Heart Rate x Stroke Volume
Factors on Cardiac Output
Stoke Volume
less out
1) Preload:
2) Afterload:
3) Contractility:
4) Heart Rate:
less in
Dual Effects
Heart Rate
CO = Heart Rate x Stroke Volume
Regulators of the Heart:
Factors Influencing Stroke Volume
Starlings Law – stretch
 Force of contraction
 Venous return:

 Skeletal pumping
 Respiratory pumping
Frank-Starling Law:
Intrinsic variation as EDV increases, so does
force of contraction (increased stretch)
Increased peripheral resistance

Increased EDV

Increased stretch

Next causes the next contraction to be stronger
Regulators of the Heart:
Factors Influencing Stroke Volume
Regulators of the Heart:
Factors Influencing Stroke Volume
Some factors that regulate
Cardiac Output:
Autonomic Nervous System
 Epinephrine and nonepinephrine
 Age
 Gender
 Physical Activity
 Body Temperature


Autonomic Nervous System:
nerve impulses are sent to the medulla,
the autonomic nervous system is then
activated and receptors will cause blood
pressure changes.

Epinephrine and nonepinephrine:
These are released into the blood, it’s a
stream when there is anxiety, stress or
increased physical activity. These
hormones promote the increased
pumping of the heart and stroke volume,
therefore increasing cardiac output.

Age:
An infant has a higher heart rate than
adults, usually at 115 beats per
minute. This slowly decreases and
stabilizes to around 100 bpm as the
person matures.

Gender:
Females have a higher resting heart
rate than in male.

Physical fitness:
A physically active person usually has a
resting heart rate at around 50 bpm.

Body temperature:
Increase in temperature will also
increase your cardiac output. Which
means that a person should be aware of
the factors to avoid applying stress and
pressure on the heart muscles.
Work Cited Page:

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http://www.provet.co.uk/equinecardiology/5a583af.htm
http://homepages.uel.ac.uk/M.S.Meah/bs250page4blec2.htm
http://74.125.47.132/search?q=cache:ciY44JDIlv0J:www.hea
lthsystem.virginia.edu/internet/anesthesiologyelective/cardiac/basicphys.cfm+cardiac+output+factors&cd=
8&hl=en&ct=clnk&gl=ca
http://www.healthmad.com/Health/Factors-Affecting-CardiacOutput.310921