the cardiovascular system and exercise

Copyright © 2006 Lippincott Williams & Wilkins.

The Cardiovascular System and Exercise The Cardiovascular

System and Exercise

Chapter 10Chapter 10


Major Cardiovascular Functions

Major Cardiovascular Functions

• Delivers oxygen to active tissues • Aerates blood returned to the lungs • Transports heat, a byproduct of

cellular metabolism, from the body’s core to the skin

• Delivers fuel nutrients to active tissues

• Transports hormones, the body’s chemical messengers


conduction of the heart SA and AV node

Valves - MATP


The Heart and the Circulatory System

Check out the link


Peripheral VasculaturePeripheral Vasculature

• Arteries– Provides the high-pressure tubing that

conducts oxygenated blood to the tissues

• Capillaries– Site of gas, nutrient, and waste exchange

• Veins– Provides a large systemic blood reservoir

and conducts deoxygenated blood back to the heart


How does blood pool in the legs?


A Significant Blood Reservoir

A Significant Blood Reservoir

• The veins do not merely function as passive conduits

• At rest, the venous system normally contains about 65% of total blood volume

• Hence, veins serve as capacitance vessels or blood reservoirs


Blood Pressure Blood Pressure

• Systolic blood pressure– Highest arterial pressure measured after

left ventricular contraction (systole)– e.g., 120 mm Hg

• Diastolic blood pressure– Lowest arterial pressure measured during

left ventricular relaxation (diastole)– e.g., 80 mm Hg


Hypotensive Recovery Response

Hypotensive Recovery Response

• After a bout of sustained light- to moderate-intensity exercise, systolic blood pressure temporarily decreases below pre-exercise levels for up to 12 hours in normal and hypertensive subjects


Myocardial Oxygen Utilization

Myocardial Oxygen Utilization

• At rest, the myocardium extracts 70 to 80% of the oxygen from the blood flowing in the coronary vessels

• Because near-maximal oxygen extraction occurs in the myocardium at rest, increases in coronary blood flow provide the only means to meet myocardial oxygen demands in exercise


Myocardial Oxygen Utilization (cont’d)Myocardial Oxygen Utilization (cont’d)

• In vigorous exercise, coronary blood flow increases 4 to 6 times above the resting level because of elevated myocardial metabolism and increased aortic pressure


Heart’s Energy SupplyHeart’s Energy Supply

• The heart relies almost exclusively on aerobic energy metabolism

• Myocardial fibers contain the greatest mitochondrial concentration of all tissues

• Myocardial fibers readily metabolize long-chain fatty acids, glucose, and lactate formed in skeletal muscle


Cardiovascular Regulation and Integration

Cardiovascular Regulation and Integration


Heart Rate Regulation Heart Rate Regulation

• Cardiac muscle possesses intrinsic rhythmicity

• Without external stimuli, the adult heart would beat steadily between 50 and 80 times each minute


Heart Pumping


ECG video


Here's a Normal EKG to Compare: Bradychardia

Tachycardia VF

asystole


Extrinsic Regulation of HRExtrinsic Regulation of HR

• Sympathetic influence – Catecholamine (NE/E)– Results in tachycardia

• Parasympathetic influence– Acetylcholine – Results in bradycardia

• Cortical influence– Anticipatory heart rate


Key PointKey Point

• Endurance training creates an imbalance between sympathetic accelerator and parasympathetic depressor activity to favor greater vagal (parasympathetic) dominance


Arrhythmias Arrhythmias

• Heart rhythm irregularities– Premature atrial contraction or PAC– Premature ventricular contraction or

PVC– Atrial fibrillation– Ventricular fibrillation


Blood Flow Regulation Blood Flow Regulation

• Flow = Pressure ÷ Resistance• Three factors determine

resistance to blood flow– Viscosity, or blood thickness– Length of conducting tube– Radius of blood vessel


Poiseuille’s Law Poiseuille’s Law

• Q = r4P/8L

– Q: flow– P: pressure gradient– r: vessel radius– L: vessel length


Local Factors Local Factors

• Enhance regional blood flow via local vasodilatation (a.k.a. autoregulation) in response to local factors

PO2 Temperature

CO2 Adenosine H+ NO K+ MG++


Neural Mechanisms Neural Mechanisms

• Central vascular control via sympathetic and, to a minor degree, parasympathetic portions of the autonomic nervous system overrides vasoregulation afforded by local factors


Hormonal FactorsHormonal Factors

• The adrenal gland releases large quantities of epinephrine and a small amount of norepinephrine

• E/NE cause a systemic constrictor response, except in blood vessels of the heart and skeletal muscle


Cardiovascular Dynamics During Exercise

Cardiovascular Dynamics During Exercise


Cardiovascular DynamicsCardiovascular Dynamics

• Q = HR × SV (Fick Equation)

– Q: cardiac output– HR: heart rate– SV: stroke volume


Close Association Between Max Q & VO2max

• An almost proportionate increase in max Q accompanies increases in VO2max with training


Q Differences: Men & Women

• Women have a 10% lower Hb level than men

• Result:– A 5–10% increase in Q at any

submax level of O2 consumption


Factors Affecting A-vo2difference

1. Redistribution of flow to active tissues during exercise

2. Increased capillary density due to training increases surface area and O2 extraction

3. Increased number and size of mitochondria

4. Increased oxidative enzymes5. Vascular and metabolic improvements


Starling Law of the HeartStarling Law of the Heart

• An increase in end-diastolic volume stretches myocardial fibers, causing a powerful ejection stroke as the heart contracts

• Improved contractility of a stretched muscle (within a limited range) probably relates to a more optimum arrangement of intracellular myofilaments as the muscle stretches


Maximal Oxygen Consumption

Maximal Oxygen Consumption

• O2max = Max Q • Max a-vO2differenceV


A-vo2 Differences

A-vo2 Difference at Rest

• 20mL O2/dL blood arterial

• 15mL O2/dL blood venous

• 5mL a-vO2diff

A-vo2 Difference During Exercise

• 20mL O2/dL blood arterial

• 5–15mL O2/dL blood venous

• Up to a 3-fold increase in O2 extraction


Physiologic Response

• Submaximal arm exercise produces:

> HR> Pulmonary ventilations> RPE> BP response

than comparable leg exercise

the cardiovascular system and exercise

Documents