BIO 238

 Heart and blood vessels are part of the cardiovascular system
 Heart pumps blood
 Arteries carry blood away from the heart to capillaries
 Veins carry blood from capillaries to heart

 Heart Chambers
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2 atria
 Receive blood from veins
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2 ventricles
 Pump blood to arteries
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Atrial septum
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Interventricular septum

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 Left atria and ventricle: left pump
 Right atria and ventricle: right pump
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 Ventricles have more muscle then atria: atria pump to ventricle, ventricles pump out to body areas
 Left ventricle is most muscular: pumps blood to body
 Right ventricle has less muscle: pumps blood to lungs only

 Heart Valves:
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Allows blood to flow in one direction Atrioventricular valves
 Allows flow from atria to ventricles
 Tricuspid valve : between R atrium and ventricle
 Bicuspid (mitral) valve : between L atrium and ventricle
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Semilunar valves
 Located at base of blood vessels attached to ventricles
 Pulmonary semilunar valve : between R ventricle and pulmonary trunk
 Aortic semilunar valve : between L ventricle and aorta

 Includes:
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Systole : contraction phase
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Diastole : relaxation phase
 When atria and ventricles are relaxed, blood flows into atria, then through open AV valves into ventricles
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Semilunar valves closed due to greater pressure in arteries than in ventricles

 Atrial systole forces more blood into relaxed ventricles

 Ventricular systole (atrial diastole) increases blood pressure in ventricles
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Closes AV valves, opens semilunar valves
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Blood moves from ventricles and into arteries

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 Deoxygenated blood flows from R ventricle to lungs
 Oxygenated blood flows from lungs to L atrium
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 Oxygenated blood flows L ventricle to body
 Deoxygenated blood flows from body to R atrium

 Steps of heart circulation
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Superior and inferior vena cava return blood from body to R atrium
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Pulmonary veins return blood from lungs to L atrium
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Atria push blood into ventricles
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R ventricle pumps blood into pulmonary trunk
 Blood moves into R and L pulmonary arteries, which head to lungs
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L ventricle pumps blood into the aorta, which carries blood out to body

 Conduction system consists of specialized muscle tissue that acts as neural tissue
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Spontaneously form impulses
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Impulses cause myocardium to contract

 Components include
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Sinoatrial (SA) node
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Atrioventricular (AV) node
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AV bundle
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Purkinje fibers

 Sinoatrial node
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Pacemaker of the heart
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Rhythmically forms impulses to initiate each heartbeat
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Impulses cause simultaneous contraction of atria
 Atrioventricular node
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Receives impulse from SA node
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Delay in passing through node allows time for ventricular filling and the completion or atrial contraction
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Passes impulse to the AV bundle

 AV bundle
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Divides into L and R branches
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Carries impulse down ventricular septum and up lateral ventricle walls
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Forms Purkinje fibers
 Purkinje fibers
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Carry impulse to myocardium of ventricles
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Contraction occurs from the apex upward

 Electrocardiogram (ECG or EKG)
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Recording of the electrical current generated during heart contraction
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Performed by an electrocardiograph

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Electrocardiogram has three distinct waves
 P wave : atrial depolarization
 QRS wave : ventricular depolarization
 T wave : ventricular repolarization

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Numerous factors can act on the SA node to increase or decrease heart rate
Autonomic Regulation
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Cardiac center in the medulla oblongata
 Stimulated by excessive blood pressure and emotional factors, such as grief and depression
 Sympathetic neurons in the cardiac center cause an increase in heart rate
 Parasympathetic neurons in the cardiac center cause a decrease in heart rate

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Age : resting rate declines with age
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Sex : females slightly faster than males
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Physical condition : good condition means lower heart rate
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Temperature : increase in temperature increases rate
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Epinephrine : increases strengthens heart rate
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Thyroxine : produces a lesser but longer lasting increase in heart rate

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Blood calcium levels
 Low levels slow heart rate
 Increased levels increase heart rate and prolong contraction
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Blood potassium levels
 Increased levels decrease both heart rate and force of contraction
 Low levels can cause abnormal heart rhythms

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Carry blood away from the heart
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Branch into smaller arteries, eventually forming arterioles
 Play an important role in controlling blood flow and blood pressure
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Most numerous and smallest vessels
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RBCs pass through one at a time
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Thin walls allow exchange of materials between blood and cells

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Blood flows from capillaries into venules
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Venules unite to form larger veins, which in turn unite to form even larger veins
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Valves exist in large veins to prevent blood backflow and aid in venous blood return
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Veins hold ~60% of blood volume at any instant
 Reducing venous volume can compensate for blood loss or increase in muscle activity

 Blood flows from high pressure areas to low pressure areas
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Greatest in ventricles and lowest in atria
 Ventricles create the pressure

 Pressure decreases with increased distance from the heart
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Due to increase in overall cross-sectional area of vessels due to branching

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Due to low pressure, veins require assistance to return blood to the heart
 Skeletal muscle contractions
 Contraction compresses veins, forcing blood from one valved segment to another
 Important in arms and legs

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 Downward contraction of diaphragm during inspiration
 Decreases thoracic pressure and increases abdominal pressure
 High pressure in abdominal veins forces blood into low pressure thoracic veins

 Arterial blood pressure in the systemic circuit
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Systolic blood pressure
 Highest pressure during ventricular systole
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Diastolic blood pressure
 Lowest pressure during ventricular diastole
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Pulse pressure is difference between systolic and diastolic blood pressures
 Causes the pulse : expansion and contraction of arterial walls

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Cardiac output
 Volume of blood pumped by heart in one minute
 Determined by heart rate and blood volume pumped in contraction
 Increase cardiac output, increase blood pressure
 Decrease cardiac output, decrease blood pressure
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Blood volume
 Decrease in blood volume, decrease in blood pressure
 Increase in blood volume, increase in blood pressure

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Peripheral resistance
 Friction of blood against blood vessel walls
 Constriction of arterioles increase both resistance and blood pressure
 Dilation of arterioles decreases both resistance and blood pressure
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Viscosity
 Thickness of blood
 Determined by blood cell concentration and plasma proteins
 Increase viscosity increases blood pressure
 Decrease viscosity decreases blood pressure

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Vasomotor center in the medulla
 Increases frequency of sympathetic impulses to cause vasoconstriction
 Increases blood pressure and velocity
 Accelerates oxygen and carbon dioxide transport rates
 Decreases frequency of sympathetic impulses to cause vasodilation
 Lowers blood pressure and velocity
 Activity of vasomotor area can be modified
 Affected by epinephrine, impulses from higher brain area, impulses from pressure and chemoreceptors
 Decrease in pressure, pH, or oxygen causes vasoconstriction

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 Oxygen, carbon dioxide, pH
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 Increases rate of exchange of materials between cells and capillaries
 Example: decrease in oxygen and increase in carbon dioxide causes vasodilation to increase blood flow

 Arrhythmia
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Abnormal heart beat
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Caused by factors such as damage to conduction system and drugs
 Bradycardia
 Heart rate less then 60 beats/min
 Tachycardia
 Heart rate over 100 beats/min
 Heart flutter
 Heart rate over 200-300 beats/min
 Fibrillation
 Very rapid heart rate with uncoordinated contraction
 Blood is not pumped from ventricles

 Congestive heart failure (CHF)
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Acute or chronic inability of hear to pump out returned to it
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Symptoms include fatigue, edema, accumulation of blood in organs
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Possible cause is atherosclerosis
 Heart murmurs
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Unusual heart sounds associated with defective heart valves
 Myocardial infarction
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Death of myocardium due to coronary artery blockage
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Heart attack
 Pericarditis
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Inflammation of pericardium due to viral or bacterial infection

 Aneurysm
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Weakened vessel wall bulges, forming balloon-like sac filled with blood
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Rupture can be fatal
 Arteriosclerosis
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Hardening of the arteries
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Due to calcium deposits accumulating in tunica media
 Atherosclerosis
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Formation of fatty deposits in the tunica interna of arteries
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Plagues reduce lumen size and increase probability of blood clot formation

 Hypertension
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Chronic high blood pressure
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Pressure exceeds 140/90
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Pre-hypertension
 A systolic pressure between 120-139 and diastolic pressure between 80-89
 Phlebitis
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Inflammation of a vein
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Most common in the legs
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Thrombophlebitis involves the formation of blood clots at the inflammation site
 Varicose veins
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Dilated, swollen veins due to malfunctioning valves
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Causes include heredity, pregnancy, and lack of physical activity
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Hemorrhoids