Cardiovascular System

Cardiovascular System Components

Circulatory system Pulmonary system

Purposes: Transport O2 to tissues and remove

waste Transport nutrients to tissues Regulation of body temperature

Circulatory System Heart

Pumps blood Arteries and arterioles

Carry blood away from heart Capillaries

Exchange nutrients with tissues Veins and venules

Carry blood toward heart

Pulmonary and Systemic Circuits Systemic Circuit

Left side of heart Pumps

oxygenated blood to body via arteries

Returns deoxygenated blood to right heart via veins

Pulmonary Circuit Right side of heart Pumps

deoxygenated blood to lungs via pulmonary arteries

Returns oxygenated blood to left heart via pulmonary veins

Cardiac Cycle Systole

Contractile phase of heart

Electrical and mechanical changes

E.g. blood pressure changes

E.g. blood volume changes

Diastole Relaxation phase

of heart Takes twice as

long as systole E.g. resting HR =

60 Systole = 0.3 s Diastole = 0.6 s

Arterial Blood Pressure Expressed as systolic/diastolic

Normal – 120/80 mmHg High – 140/90 mmHg

Systolic pressure (top number) Pressure generated during ventricular

contraction Diastolic pressure

Pressure during cardiac relaxation

Blood Pressure Pulse Pressure (PP)

Difference between systolic and diastolic

PP = systolic - diastolic Mean Arterial Pressure (MAP)

Average pressure in arteries MAP = diastolic + 1/3 (systolic –

diastolic)

Causes of High Blood Pressure

Age Race Heredity Diet Stress Inactivity

Electrical Activity of the Heart Contraction of heart depends on

electrical stimulation of myocardium

Impulse is initiated on right atrium and spreads throughout the heart

May be recorded on an ECG

Electrocardiogram Records electrical activity of the

heart P wave

Atrial depolarization QRS complex

Ventricular depolarization T wave

Ventricular repolarization

Diagnostic use of the ECG ECG abnormalities may indicate

coronary heart disease ST-segment depression may

indicate myocardial ischemia

Cardiac Output - Q Q = HR x SV or Q = (FH) (Vs) Where: Q = volume of blood pumped by

left ventricle each minute (L.min) fH = heart rate (b.min) Vs = stroke volume (average

volume of blood pumped per each contraction (L.b)

Cardiac Output Range of normal at rest is 4 – 6

L.min During aerobic activity the

increase in cardiac output is roughly proportional to intensity.

Max. Q is in range of 20 – 40 L.min, depending on size, heredity, and conditioning.

Heart Rate Range of normal at

rest is 50 – 100 b.m Increases in

proportion to exercise intensity

Max. HR is 220 – age Medications or upper

body exercise may change normal response

Stroke Volume Range of normal at rest is 60 – 100 ml.b During exercise, SV increases quickly,

reaching max. around 40% of VO2 max. Max. SV is 120 – 200 ml.b, depending on

size, heredity, and conditioning. Increased SV during rhythmic aerobic

exercise is due to complete filling of ventricles during diastole and/or complete emptying of ventricles during systole.

Central Circulation Maintenance Important for older or deconditioned

adults Moderate, continuous, rhythmic aerobic

activity encourages venous return Strenuous activity and held muscle

contractions should be avoided Taper or cool down should follow each

activity session to encourage venous return

Frank-Starling Law of the Heart The heart will pump all the blood

returned to it by the venous system. Central circulation must be maintained and the veins must continuously return blood to the heart.

Features that Encourage Venous Return One-way valves in veins Vasoconstriction of blood flow to inactive

body parts Pumping action of skeletal muscles in

arches of feet, calves, thighs, etc. Pressure changes in chest and abdomen

during breathing Maintenance of blood volume by

adequate fluid replacement Siphon action of vascular system

Features that Inhibit Venous return Heat stress requiring additional blood flow

to the skin for core temp. maintenance Dehydration from sweating or from limiting

fluid intake (dieting, making weight) Held muscle contractions that cause blood

to pool in the extremities A Valsalva maneuver which increases

pressure in the chest to a high level Changing from a horizontal to a vertical

position abruptly

Autonomic Nervous System Control of Heart Rate Sympathetic

control Stimulates “fight

or flight” response Speeds up heart

rate and stroke volume

Sympathetic tone > 100 bpm

Parasympathetic control Connected to

vagus nerves Slows down heart

rate Parasympathetic

tone 60 – 100 bpm

Skeletal Muscle Pump Rhythmic skeletal muscle

contractions force blood in the extremities toward the heart

One-way valves in veins prevent backflow of blood

Components of Blood Plasma

Liquid portion of blood Contains ions, proteins, hormones

Cells Red blood cells

Contain hemoglobin to carry oxygen White blood cells Platelets

Important in blood clotting Hematocrit

Percent of blood composed of cells

Oxygen Delivery During Exercise Oxygen demand by muscles during

exercise is many times greater than at rest

Increased oxygen delivery accomplished by: Increased cardiac output Redistribution of blood flow to

skeletal muscle

Changes in Cardiac Output Cardiac output increases due to:

Increase in heart rate Linear increase to max

Max HR = 220 - age Increased stroke volume

Plateau at ~40% of VO2 max

Oxygen uptake by the muscle also increases Higher arteriovenous difference

Redistribution of Blood Flow Increased blood flow to working

skeletal muscle Reduced blood flow to less active

organs Liver, kidneys, GI tract

Increased blood flow to skeletal muscle during exercise

Withdrawal of sympathetic vasoconstriction

Autoregulation Blood flow increased to meet

metabolic demands of tissue O2 tension, CO2 tension, ph,

potassium, adenosine, nitric oxide

Circulatory Responses to Exercise Heart rate and blood pressure Depend on:

Type, intensity, and duration of exercise

Environmental condition Emotional influence

Transition from rest > exercise and exercise > recovery

Rapid increase in heart rate, stroke volume, and cardiac output

Plateau in submaximal exercise Recovery depends on:

Duration and intensity of exercise Training state of subject

Incremental Exercise Heart rate and cardiac output

Increase linearly with increased work rate Reach plateau at 100% VO2 max

Systolic blood pressure Increases with increased work rate

Double product Increases linearly with exercise intensity Indicates the work of the heart Double product = heart rate x systolic blood

pressure

Arm vs Leg Exercise At the same oxygen uptake arm

work results in higher: Heart rate

Due to higher sympathetic stimulation Blood pressure

Due to vasoconstriction of large inactive muscle mass

Prolonged Exercise Cardiac output is maintained

Gradual decrease in stroke volume Gradual increase in heart rate

Cardiovascular drift Due to dehydration and increased

skin blood flow (rising body temperature)

How to have a heart attack

Everyone’s doing it, so it must be the “in” thing to do

Be Old Relative risk of CHD increases with

age

Have a family history of CHD The more blood relatives one has

with CHD, and the younger they are (were), the higher the relative risk

Heredity influences your cardiovascular fitness

Genetics is important - pick your parents carefully

High/low responders to training

If you do the process, the product will follow, within your limitations

Be a Man Males have 5-6 times the relative

risk of CHD of females

Why? Estrogen may be protective

Unalterable Risk Factors for CHD Age Family History Sex

Alterable Risk Factors Things you can do something

about…

Be fat Obesity increases CHD risk

How much fat is too much? Males - > 25% Females > 30%

Eat a high fat diet High fat foods increase plaque

within arteries and contribute to atherosclerosis

Have High Cholesterol Total cholesterol/HGH ratio above: Males – 4.5/1 Females – 4/1 Increases relative risk of CHD

Have High Blood Pressure High blood pressure forces the

heart to work harder

How high is too high?

> 140/90

Smoke Smokers are more likely to die of

heart attack than cancer

Smoking is the single most important alterable risk factor

Be a Type A personality Type A personalities are:

High-strung Achievement-oriented Aggressive Time-conscious

Live a stressful lifestyle No one, lying on their deathbed,

has said they wished they had spent more time at the office.

Have Other Hypokinetic Diseases Diabetes Ulcers Obesity

Don’t Exercise If you get the urge to exercise, lie

down until the feeling passes.

FIT Principle for CV Fitness Frequency –

3-6x/wk Intensity – 40-85%

HR reserve

or 55-

90% max HR

Time – 20-30 min.

Field Tests of CV Fitness 12 minute run 1.5 mile run/walk Step test Bike ergometer test Rockport walk test PACER test

Telemetry HR monitors Uses radio signals to transmit data Useful in clinical & performance

settings Reasonably accurate Affected by stress, excitement Can predict energy cost b/c of linear

rel’t between HR and VO2.

Rating of Perceived Exertion (RPE) 6 7 very, very light 8 9 very light 10 11 fairly light 12 13 somewhat hard 14 15 hard 16 17 very hard 18 19 very, very hard