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Chapter 3.8 Cardiac Output

BOOK TITLE: Understanding Medical Physiology: A Textbook for Medical Students

Author
1. Bijlani R.L.
ISBN
9788180612213
DOI
10.5005/jp/books/10999_23
Edition
3/e
Publishing Year
2004
Pages
8
Author Affiliations
1. All India Institute of Medical Sciences, New Delhi
Chapter keywords
blood pumped, cardiac index, stroke volume, oxygen difference, arteriovenous, peripheral vein, blood temperature, dye dilution method, thermal dilution method, ventricular filling, pumping action, humoral influences, brachiocephalic trunk, thermoneutral zone, cardiac catheterization

Abstract

This chapter discusses cardiac output, where function of the heart is to pump blood. Cardiac function is best expressed in quantitative terms as the amount of blood pumped in unit time. Since blood is pumped during every heart beat, the amount pumped in unit time depends both on the amount pumped during every beat, and the number of beats per unit time. Cardiac output is the output of either ventricle. Cardiac output is distributed as blood flow to various organs. During exercise, the cardiac output may increase up to about five-fold even in untrained persons, and up to about ten-fold in trained athletes. Cardiac output is the product of stroke volume and heart rate. Parasympathetic stimulation reduces heart rate while sympathetic nerve stimulation or release of catecholamines from the adrenal medulla increases heart rate. The initial ventricular muscle fiber length is directly related to the end-diastolic ventricular volume.

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