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.

Cardiac output = stroke volume X cardiac rate

(ml/min) (ml/beat) (beats/min)

At 70 beats/min and 80 ml/beat, this results inapproximately 5.5 liters per minute

Equation:

Cardiac Output: Heart Rate X Stroke Volume

Regulation of cardiac rate

Rhythm is set by the SA node

Sympathetic nervesepinephrine and nonepinephrinestimulate opening of calcium and sodiumchannels; increase cardiac rate

Parasympathetic (vagus) nervesacetylcholine promotes opening of potassiumchannels; 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 activityand pressure in aorta and carotid arteries

Regulation of stroke volume

End-Diastolic Volume (blood left in ventriclesafter diastole)increase in EDV increase in stroke volume

Total peripheral resistance to arterial blood flowstroke volume is temporarily inversely proportionalto this

Contractility:

Innervation from sympathetic nervesRaises 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)

More in

More out

Factors on Cardiac Output  

1) Preload:  

Preload cardiac output

(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

less in

less out

Factors on Cardiac Output  

1) Preload: 2) Afterload:  3) Contractility:4) Heart Rate:

Dual Effects Heart Rate

Stoke Volume

CO = Heart Rate x Stroke Volume

Regulators of the Heart: Factors Influencing Stroke Volume

Starlings Law – stretch Force of contraction Venous return:

Skeletal pumpingRespiratory pumping

Frank-Starling Law:

Intrinsic variation as EDV increases, so doesforce 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: 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.healthsystem.virginia.edu/internet/anesthesiology-elective/cardiac/basicphys.cfm+cardiac+output+factors&cd=8&hl=en&ct=clnk&gl=ca

http://www.healthmad.com/Health/Factors-Affecting-Cardiac-Output.310921