Download - Cardiovascular System
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)
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
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
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