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Chapter 5 The Cardiovascular System Learning Objectives • Know the components of the cardiovascular system. • Know the basic, general anatomy and physiology of the cardiovascular system. • Understand the responses of the cardiovascular system during exercise. • Understand the responses of the cardiovascular system to exercise training. Cardiovascular System Composition & Primary Function • Heart • Blood vessels • Blood 1 The Heart— Its Function as 2 Pumps Types of Blood Vessels • • • • • • Arteries Veins Pulmonary veins Arterioles Capillaries Venules Anatomy of the Heart • Four chambers • A muscular organ w/ striated muscle – Muscle fibers are stimulated by the nervous system, which triggers contractions 2 Basic Anatomy of the Heart Origin of Electrical Activity in the Heart • Normal conditions in an intact heart: • Abnormal conditions in which SA slows its impulse frequency Conducting System of the Heart 3 The Cardiac Cycle • The heart’s cyclical pattern of contraction & relaxation – Diastole – Systole • Unidirectional blood flow – Regulated by valves, which are critical for preventing backflow of blood & for blood pressure • Atrial contraction • Ventricular contraction (continued) The Cardiac Cycle (continued) • End diastolic volume (EDV) – Amount of blood in each ventricle at the end of diastole • End systolic volume (ESV) – Amount of blood in each ventricle at the end of systole • Stroke volume (SV) – The difference between EDV and ESV (the amount of blood ejected out of each ventricle with each cardiac contraction) Events of the Cardiac Cycle 4 Cardiac Output • The amount of blood ejected by the heart each minute: Formula for Determining Cardiac Output Control of Heart Rate & Stroke Volume • Heart rate is influenced by the effect of the autonomic nervous system on the SA node. • Stroke volume is determined largely by end diastolic volume, which is related to ventricular contraction force. – The Frank-Starling law of the heart 5 Factors Affecting Heart Rate Factors Affecting Stroke Volume One-Way Valves of the Veins 6 Clinical Application: Heart Murmurs • May be caused by irregularities in vessel walls or malformed cardiac valves, and may result in regurgitation of blood or restricted blood flow—and cause the heart to work harder. • The heart compensates for increase in retained blood by increasing its contraction force and consuming more oxygen. • In some cases, heart murmurs may severely limit exercise tolerance. Your Viewpoint • Exercise programs can be beneficial for so many different health problems, but patients with heart murmurs may have damaged heart valves. What would you counsel such a patient about engaging in strenuous exercise? Heart Rate Is More Important than Stroke Volume in Aerobic Exercise • • • Stroke volume ↑s very little w/ ↑ in metabolism, until it levels out at approximately 8x the resting level. Heart rate is proportional to the work load imposed. Heart rate is proportional to oxygen consumption during exercise. 7 Typical Heart Rate Response to Exercise Heart Rate ∆s in a Moderately Conditioned, Middle-Aged Subject ∆s in Cardiovascular Function Following Endurance Training 8 Effects of Training on the Heart • Both resting heart rate and heart rate for a given submaximal exercise load ↓ • Stroke volume ↑s • Three mechanisms work to meet demands on tissues during intense exercise: – Reserve of heart rate – Stroke volume reserve – Greater extraction of oxygen from blood Graphic Representation of Changes during Continuous, Moderate Intensity Exercise Anatomy of Blood Vessels • Aorta and large arteries – Allow vessels to distend and recoil • Arterioles – Act as resistance vessels, which protect capillaries • Venules and veins – Serve as collecting vessels, draining various tissues 9 Hemodynamics: Principles Governing Blood Flow Distribution of Blood to Systemic Tissues At Rest and During Heavy Exercise Microcirculation • Well-organized network in which arterioles give rise to metarterioles • True capillaries arise from metarterioles • AV shunts provide another route for blood flow 10 Diagram of Microcirculation Blood Distribution • Blood flow to the tissues is controlled by changes in the diameter of small arteries & arterioles • Two mechanisms: Blood Pressure • Is the driving force for moving blood through the circulatory system • Plays a role in health problems such as heart attacks, stroke & kidney disease • Affected by several factors: Age, gender, emotional state, time of day & body position • Defined as systolic pressure over diastolic pressure • Measured by a sphygmomanometer 11 Blood Pressure ∆s During Exercise • Rhythmic exercise— • Isometric or static exercise— Typical Time Course of the Arterial Blood Pressure Response in a Healthy Young Male Where to Learn More • Cardiovascular system: – www.innerbody.com/image/cardov.html • American Heart Association: – www.americanheart.org • Heart.org: – www.theheart.org/index.cfm • American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR): – www.aacvpr.org 12 Can you? • Describe normal cardiorespiratory responses to static and dynamic exercise in terms of heart rate, blood pressure, and oxygen consumption? – What sort of cardiorespiratory response would you expect to see when someone is pushing a heavy sofa that does not move? – What response would you expect to see in someone who is cleaning his house? 13