Cardiovascular System

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• Cardiovascular System
• The Heart

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Functions of the Heart

• Generating blood pressure
• Routing blood
• Heart separates pulmonary and systemic
  circulations
• Ensuring one-way blood flow
• Heart valves ensure one-way flow
• Regulating blood supply
• Changes in contraction rate and force match blood
  delivery to changing metabolic needs

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Size, Shape, Location of the Heart

• Size of a closed fist
• Shape
• Apex Blunt rounded point of cone
• Base Flat part at opposite of end of cone
• Located in thoracic cavity in mediastinum

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Heart Cross Section
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Pericardium
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Heart Wall

• Three layers of tissue
• Epicardium This serous membrane of smooth outer
  surface of heart
• Myocardium Middle layer composed of cardiac
  muscle cell and responsibility for heart
  contracting
• Endocardium Smooth inner surface of heart
  chambers

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Heart Wall
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External Anatomy

• Four chambers
• 2 atria
• 2 ventricles
• Auricles
• Major veins
• Superior vena cava
• Pulmonary veins
• Major arteries
• Aorta
• Pulmonary trunk

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External Anatomy
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Coronary Circulation
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Heart Valves

• Atrioventricular
• Tricuspid
• Bicuspid or mitral
• Semilunar
• Aortic
• Pulmonary
• Prevent blood from flowing back

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Heart Valves
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Function of the Heart Valves
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Blood Flow Through Heart
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Systemic and PulmonaryCirculation
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Heart Skeleton

• Consists of plate of fibrous connective tissue
  between atria and ventricles
• Fibrous rings around valves to support
• Serves as electrical insulation between atria and
  ventricles
• Provides site for muscle attachment

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Cardiac Muscle

• Elongated, branching cells containing 1-2
  centrally located nuclei
• Contains actin and myosin myofilaments
• Intercalated disks Specialized cell-cell
  contacts
• Desmosomes hold cells together and gap junctions
  allow action potentials
• Electrically, cardiac muscle behaves as single
  unit

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Conducting System of Heart
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Electrical Properties

• Resting membrane potential (RMP) present
• Action potentials
• Rapid depolarization followed by rapid, partial
  early repolarization. Prolonged period of slow
  repolarization which is plateau phase and a rapid
  final repolarization phase
• Voltage-gated channels

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Action Potentials inSkeletal and Cardiac Muscle
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SA Node Action Potential
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Refractory Period

• Absolute Cardiac muscle cell completely
  insensitive to further stimulation
• Relative Cell exhibits reduced sensitivity to
  additional stimulation
• Long refractory period prevents tetanic
  contractions

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Electrocardiogram

• Action potentials through myocardium during
  cardiac cycle produces electric currents than can
  be measured
• Pattern
• P wave
• Atria depolarization
• QRS complex
• Ventricle depolarization
• Atria repolarization
• T wave
• Ventricle repolarization

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Cardiac Arrhythmias

• Tachycardia Heart rate in excess of 100bpm
• Bradycardia Heart rate less than 60 bpm
• Sinus arrhythmia Heart rate varies 5 during
  respiratory cycle and up to 30 during deep
  respiration
• Premature atrial contractions Occasional
  shortened intervals between one contraction and
  succeeding, frequently occurs in healthy people

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Alterations in Electrocardiogram
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Cardiac Cycle

• Heart is two pumps that work together, right and
  left half
• Repetitive contraction (systole) and relaxation
  (diastole) of heart chambers
• Blood moves through circulatory system from areas
  of higher to lower pressure.
• Contraction of heart produces the pressure

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Cardiac Cycle
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Events during Cardiac Cycle
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Heart Sounds

• First heart sound or lubb
• Atrioventricular valves and surrounding fluid
  vibrations as valves close at beginning of
  ventricular systole
• Second heart sound or dupp
• Results from closure of aortic and pulmonary
  semilunar valves at beginning of ventricular
  diastole, lasts longer
• Third heart sound (occasional)
• Caused by turbulent blood flow into ventricles
  and detected near end of first one-third of
  diastole

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Location of Heart Valves
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Mean Arterial Pressure (MAP)

• Average blood pressure in aorta
• MAPCO x PR
• CO is amount of blood pumped by heart per minute
• COSV x HR
• SV Stroke volume of blood pumped during each
  heart beat
• HR Heart rate or number of times heart beats per
  minute
• Cardiac reserve Difference between CO at rest
  and maximum CO
• PR is total resistance against which blood must
  be pumped

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Factors Affecting MAP
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Regulation of the Heart

• Intrinsic regulation Results from normal
  functional characteristics, not on neural or
  hormonal regulation
• Starlings law of the heart
• Extrinsic regulation Involves neural and
  hormonal control
• Parasympathetic stimulation
• Supplied by vagus nerve, decreases heart rate,
  acetylcholine secreted
• Sympathetic stimulation
• Supplied by cardiac nerves, increases heart rate
  and force of contraction, epinephrine and
  norepinephrine released

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Heart Homeostasis

• Effect of blood pressure
• Baroreceptors monitor blood pressure
• Effect of pH, carbon dioxide, oxygen
• Chemoreceptors monitor
• Effect of extracellular ion concentration
• Increase or decrease in extracellular K
  decreases heart rate
• Effect of body temperature
• Heart rate increases when body temperature
  increases, heart rate decreases when body
  temperature decreases

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Baroreceptor and ChemoreceptorReflexes
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Baroreceptor Reflex
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Chemoreceptor Reflex-pH
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Effects of Aging on the Heart

• Gradual changes in heart function, minor under
  resting condition, more significant during
  exercise
• Hypertrophy of left ventricle
• Maximum heart rate decreases
• Increased tendency for valves to function
  abnormally and arrhythmias to occur
• Increased oxygen consumption required to pump
  same amount of blood