Cardiovascular System

Cardiovascular System Components Circulatory system Pulmonary system Purposes: Transport O 2 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 = (F H) (V s ) Where: Q = volume of blood pumped by left ventricle each minute (L. min) f H = 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 VO 2 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 = age Increased stroke volume Plateau at ~40% of VO 2 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 O 2 tension, CO 2 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% VO 2 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 % max HR Time – 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 VO 2.

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