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Cardiovascular System The Heart. 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

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Presentation Transcript
functions of the heart
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
size shape location of the heart
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
heart wall
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
external anatomy
External Anatomy
  • Four chambers
    • 2 atria
    • 2 ventricles
  • Auricles
  • Major veins
    • Superior vena cava
    • Pulmonary veins
  • Major arteries
    • Aorta
    • Pulmonary trunk
heart valves
Heart Valves
  • Atrioventricular
    • Tricuspid
    • Bicuspid or mitral
  • Semilunar
    • Aortic
    • Pulmonary
  • Prevent blood from flowing back
heart skeleton
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
cardiac muscle
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
electrical properties
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
refractory period
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
electrocardiogram
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
cardiac arrhythmias
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
cardiac cycle
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
heart sounds
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
mean arterial pressure map
Mean Arterial Pressure (MAP)
  • Average blood pressure in aorta
  • MAP=CO x PR
    • CO is amount of blood pumped by heart per minute
      • CO=SV 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
regulation of the heart
Regulation of the Heart
  • Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation
    • Starling’s 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
heart homeostasis
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
effects of aging on the heart
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