Chapter 15

Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

Chapter 15

The Cardiovascular System


Cardiovascular System Components

• Heart: Pump

• Arteries, Arterioles: Distribution system

• Capillaries: Exchange vessels

• Veins: Collection and return system



The Heart

• Myocardium

– Striated lattice-like network

– Functions as a unit


Functions of the Heart

• Functions of right side– Receive blood returning from body– Pump blood to lungs for gas exchange

• Functions of left side– Receive oxygenated blood from lungs– Pump blood into systemic circulation



The Arterial System

• AortaArteriesArterioles

• Vessels have endothelial tissue, smooth muscle, and connective tissue.



Blood Pressure

• Pressure generated by the pumping action of the heart and the resistance of the blood vessels

• BP = Cardiac output × Total peripheral resistance


Blood Pressure

• Systole

– Contraction phase

• Diastole

– Relaxation phase




Blood Pressure Measurement

• Auscultation method– Listen for Korotkoff sounds.– Use a stethoscope and sphygmomanometer.


Mean Arterial Pressure

• MAP = Diastolic BP + [0.333 (Systolic − Diastolic)]

• Reveals information regarding workload of the heart


Capillaries

• Microscopic vessels 7 – 10 m in diameter

• Contain 6% of total blood volume

• Walls contain one layer of epithelial cells

• Skeletal muscles have a dense capillary network.

• Myocardium has an even denser network.


Blood Flow in Capillaries

• Precapillary sphincters regulate flow.

• Capillaries open and flow increases during exercise.




Venous Return

• One-way valves prevent back flow.

• Veins serve a capacitance role.– At rest, ~ 65% of blood is on the venous side

of the system.


Varicose Veins• When one-way valves become defective,

blood pools.

• Usually occurs in surface veins– Less musculature to help compress vessels– Occurs most frequently in legs

• Phlebitis– Severe varicose veins with inflammation


Venous Pooling

• Muscle pump – Prevents pooling and edema– Directs blood back towards the heart


Hypertension

• Chronically elevated blood pressure

> 140 / 90 mm Hg

• Imposes a strain on the CV system

• It is a prevalent disorder.


Effective Treatment

• Medications

• Regular physical activity

• Weight loss

• Stress management

• Decreased sodium intake

• Decreased alcohol consumption


BP Response to Exercise

• Resistance exercise– Straining compresses vessels.– Peripheral resistance increases.– Blood pressure increases in an attempt to

perfuse tissues.


Steady-Rate Exercise

• Systolic pressure increases with increases in workload.– There is a linear relationship between

workload and systolic BP.

• Diastolic pressure remains fairly constant.



BP Response to Upper-Body Exercise

• Resistance to flow is increased with upper-body exercise.

• Smaller vessels in upper body compress more easily.

• Care is required for individuals with heart and valve diseases.


BP in Recovery

• Following endurance exercise, there is a hypotensive response.

• BP temporarily falls below normal resting values.

• Regular exercise may help control moderate hypertension.


The Heart’s Blood Supply

• Coronary circulation– Right and left coronary arteries branch off the

upper ascending aorta.– RCA supplies predominantly the right atrium

and ventricle.– LCA supplies the left atrium and ventricle and a

small portion of the right ventricle.



Myocardial O2 Use

• At rest, myocardium extracts ~ 70 – 80% available O2.

• During exercise, flow must increase to meet O2 demand.– Flow may increase 4 – 6 times.


Effects of Impaired Blood Supply

• Impaired flow usually results in angina pectoris.

• If flow is severely reduced, myocardial infarction may result.


Rate-Pressure Product: An Estimate of Myocardial Work

• Rate-Pressure Product or Double Product

RPP = SBP × HR

• Is a commonly used measure of myocardial work


Myocardial Metabolism

• Myocardium has a significantly higher mitochondrial density compared with skeletal muscle.

• This allows the heart to utilize– Glucose– Fatty acids– Lactate


Myocardial Metabolism

• Endurance exercise training increases the ability to use lactate and fatty acids for fuel.

• Decrease reliance on CHO


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Chapter 15