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Trauma | Cardiovascular System

Cardiovascular system

Stroke volume: amount of blood pumped into the cardiovascular system in one heart contraction. Amount is usually around 70mL. Depends on:

  • Contractility: the extent and velocity of muscle fiber shortening
  • Preload: the passive stretching force on the ventricular muscle at the end of diastole. More blood returning increases the preload, less blood returning decreases it. If the container (vessels) is greater than the fluid, you’ll have inadequate preload and a decrease in cardiac output.
  • Afterload: the pressure the ventricular muscles must generate to overcome the higher pressure in the aorta, and eject the blood out.

Blood Pressure: the force that blood exerts against the walls of the arteries as it passes.
Cardiac Output: amount of blood pumped each minute. Heart rate x stroke volume.

Cardiovascular system is closed so increasing cardiac output or vascular resistance increases blood pressure. Decreasing cardiac output or vascular resistance decreases BP.

Blood Vessels: closed system, sometimes called “the container

  • Elastic, always adjusting their diameter
  • Responding to local tissue needs, bypassing less important tissues for vitals
  • Sympathetic nervous system activates dilation and contraction

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