Cardiac output describes how much blood each ventricle pumps in one minute. It connects the heart’s pumping rate with the volume moved by each contraction, making it a useful measure of cardiac performance at rest and during exercise.
Heart rate is measured in beats per minute, and stroke volume is the volume ejected by a ventricle in one beat. For example, at a resting HR of 75 beats per minute and an SV of 70 mL, CO is 5,250 mL/min, or 5.25 L/min. This value applies to each ventricle separately.
All flashcards
What is cardiac output?
The volume of blood pumped by one ventricle in one minute; it is calculated as heart rate multiplied by stroke volume.
How is stroke volume calculated from ventricular volumes?
Subtract end-systolic volume (ESV) from end-diastolic volume (EDV): SV=EDV−ESV.
What is ejection fraction?
The percentage of end-diastolic volume ejected during a contraction, calculated as SV/EDV×100 percent.
What is cardiac reserve?
The difference between maximum and resting cardiac output; it indicates how much additional pumping capacity the heart can provide.
What are adult bradycardia and tachycardia?
Bradycardia is a resting HR below 60 beats/min, and tachycardia is a resting HR above 100 beats/min. Symptoms and individual context are important.
Quiz questions
When arterial pressure rises and baroreceptor stretch increases, what autonomic response generally tends to lower heart rate?Answer: Parasympathetic activity increases while sympathetic activity decreases.
What is a typical cardiac effect of norepinephrine binding to beta-1 receptors?Answer: It increases depolarization rate, heart rate, and contraction strength.
When increased venous return stretches the atria, what response is associated with the Bainbridge reflex?Answer: Heart rate increases to accommodate the greater incoming blood flow.
Within physiological limits, what does the Frank–Starling mechanism predict when ventricular filling increases?Answer: Greater fiber stretch produces a stronger contraction and larger stroke volume.
What can increased afterload do to ventricular ejection?Answer: It can reduce stroke volume and leave more blood as end-systolic volume.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.