Heart & Circulatory System

Heart – Circulatory System: heart, blood, and vessels. 8-12 oz. Muscle is called myocardium. Specialized, self contained unit

  1. Deoxygenated blood> superior and inferior vena cava>
  2. Right Atrium> tricuspid valve>
  3. Right Ventricle> semi-lunar valve > pulmonary arteries> lungs heartcirc
  4. Oxygenated blood>pulmonary veins>
  5. Left Atrium>bicuspid valve
  6. Left Ventricle> semi lunar valve> aorta

Cardiac Cycle:

Systolic BP – pressure in the arteries as the left ventricle contracts
Diastolic BP – relaxation phase, pressure in the arteries at rest
Normal     Systolic    100 – 140
                   Diastolic  50 – 90

Cardiac Electrical System

  1. Contraction starts at the Sino Atrial node> intra-atrial pathway>
  2. Atrio-ventricular node> bundle is His> divides to the right bundle branch and the left bundle branch
  3. Purkinjes fibers take the impulse to the individual cells

                                             Cardiac Volume = Stroke volume x heart rate

Regulation and Heart Function – rate and speed

  1. Baro-recepters respond to changes in pressure of heart or main arteries
  2. Chemo-receptors sense changes in the chemical composition of blood (like low O2)

Normal pressure is regulated by monitoring:

_ Blood volume

_ Constriction of arteries

_ Force of cardiac contraction


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