By: Affan Malik Physiology 1 Case Study Cardiac output Factors
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
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 proportional to this
Contractility: Innervation from sympathetic nerves Raises calcium levels (positive inotropic effect)
Factors on Cardiac Output • Preload: • 2) Afterload: • 3) Contractility: • 4) Heart Rate:
Factors on Cardiac Output • Preload: Preload cardiac output (Starling-Frank Mechanism)
More out • Factors on Cardiac Output • Preload: More in Preload cardiac output (Starling-Frank Mechanism)
Factors on Cardiac Output • Preload: • 2) Afterload: R afterload CO
Factors on Cardiac Output • Preload: • 2) Afterload: • 3) Contractility: contractility CO
Factors on Cardiac Output • Preload: • 2) Afterload: • 3) Contractility: • 4) Heart Rate: Dual Effects CO = Heart Rate x Stroke Volume
Factors on Cardiac Output • Preload: • 2) Afterload: • 3) Contractility: • 4) Heart Rate: Stoke Volume less out less in Heart Rate Dual Effects 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
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://188.8.131.52/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