Heart Circulation

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HeartCirculation Physiology

• Ch. 18

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Blood Pathway

• Pulmonary circulation to and from lungs (right
  side of heart)
• Systemic circulation to and from body (left
  side)
• Renal to and from kidneys
• Hepatic portal to and from liver
• Coronary to and from heart muscle

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Heart Valves

• Direct blood flow in one direction
• AV (atrio-ventricular) valves supported by
  chordae tendonae open when atria contract
• Right AV tricuspid valve
• Left AV bicuspid or mitral valve

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• Semi-lunar valves open when ventricles contract
• Aortic valve between left ventricle and aorta
• Pulmonary valve between right ventricle and
  pulmonary trunk

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• Problems when valves prolapse or suffer from
  stenosis (scarring) can happen due to genetic
  defects, strep infections, or heart disease

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Coronary Circulation

• Myocadium too thick for diffusion of blood from
  heart chambers to be effective
• Coronary arteries supply blood to heart muscle.

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• Arteries branch from base of aorta and form a
  crown around the heart
• Cardiac veins collect and return blood to
  circulation

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• Problems happen when blockages occur
• Angina pectoris chest pain
• Myocardial infarction cardiac muscle death,
  coronary, heart attack

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Heart Physiology

• Nodal System intrinsic system
• SA Node sinus rhythm
• AV Node nodal rhythm (.04 secs)

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• Circuit
• Starts with SA node ----AV node ------ AV Bundle
  (Bundle of His)
• Bundle branches (Purkinje fibers)

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• Contraction from apex upwards
• Entire process takes .22 secs
• Rate controlled by sympathetic and
  parasympathetic

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• Problems
• Arrythmias irregular rhythm
• Fibrillation ineffective ventricular
  contraction
• Ectopic focus development of new pacemaker
  which interferes with normal pacemaker

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• Extrasystole premature contraction
• Heart block no AV node requires artificial
  pacemaker (2 kinds fixed rate and on-demand)

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Cardiac Cycle

• All events associated with blood flow through
  heart during one heart beat
• Systole contraction of ventricles
• Diastole relaxation of ventricles
• At 75 bpm average cycle is 0.8 secs

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• Heart sounds
• lub AV valve closes, louder, longer and more
  resonant
• dub SL valve snaps shut, short, sharp
• Left side usually closes before right side, so
  sounds of individual valves can be distinguished

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• Murmurs abnormal or unusual sounds occurs when
  normally smooth blood flow strikes obstructions
  or flows in the wrong direction, flow is
  turbulent and generates sounds.

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Electrocardiogram (EKG)

• Measurement of electrical output of the hearts
  electrical system
• Consists of 3 types of deflection waves
• P wave impulse from SA node

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• QRS wave depolarization of ventricles (unequal
  in size due to size differences of ventricles)
• T wave repolarization of ventricles

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• P-R beginning of atrial excitation
• Q-T beginning of ventricle contraction

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Regulation of Rate

• Nervous Control
• Sympathetic releases norepinephrine to stimulate
  SA and AV nodes stress (emotional or physical)
• Parasympathetic (via vagus nerves) releases ACh
  to slow things down

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• Chemical control
• Hormones
• Epinephrine
• Thyroxine

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• atrial natriuretic factor (ANF) - causes
  vasodilation and kidneys to dump water lowers
  blood pressure
• Antidiuretic hormone (ADH) vasoconstriction and
  tells kidneys to hold water alcohol interfers
  with this

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• Physical factors
• Age
• Gender
• Exercise
• Body temperature
• Fetal rate 2x adult

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Pathology

• Tachycardia rapid heart rate
• Bradycardia slow heart rate
• Congestive heart failure ventricles dont pump
  effectively, circulation is inadequate
• Pulmonary congestion left side fails
• Systemic congestion right side fails

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• Hypotension
• Hypertension (silent killer) stresses myocardium
  which enlarges heart, vessels tear which
  increases platelet deposition and Ca deposits

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Any Questions?