Summary: Pathophysiology Of Heart & Circulatory System

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• 1 Lecture 1 - Cardiac energetics

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• Where in the circulation is the greatest oxygen pressure drop, and what are (roughly) the differences in oxygen pressure (mmHg)?

  - Greatest pressure drop: in systemic circulation
  - PO2 from lungs to left heart to tissue: 105-100
  - PO2 from systemic circulation to right heart to lungs: 40 - 15 (lowest upon exercise).

• What are the differences in blood pressure in the circulation?

  - From LV to systemic circulation: 120/80
  - From systemic circulation back to heart: 25/4

• At what four processes in the body is oxygen flow regulated?

  1. Ventilation (breathing)
  2. O2 diffusion in lungs
  3. Cardiac function (among others determined by O2 content in arterial blood - O2 content in venous blood)
  4. O2 diffusion in muscles (or other tissue?)

• What units do muscles consist of?

  - bundles of muscle fibers
  - muscle fibers consist of myofibrils

• What is the smallest unit of the muscle, and what does it require?

  - the sarcomere (contractile unit),
  - which requires ATP

• How does muscle contraction work?

  Stimulus → depolarization → Ca2+ influx (passive, along gradient) → Ca2+ binds to troponin → tropomyosin & myosin bind to actin → muscle contraction.

• Why is ATP needed for the contraction of sarcomeres, and where does this ATP come from?

  - ATP is needed for the reuptake of Ca2+,
  - and this ATP mostly comes from the mitochondria

• What is measured in a cardiopulmonary exercise test?

  - VO2(max),
  - which is the maximum rate of oxygen consumption attainable during physical exertion (e.g. endurance)
  - In this test, the expected VO2(max) is compared to the actual VO2(max).

• How do people with cardiac failure typically perform on a cardiopulmonary exercise test?

  Their VO2 is quite low.

• When is the 'atrial kick' more pronounced?

  When the heart is more stiff (because it's harder for the atria to fill the ventricles).