Summary: Physiology: Cardiology

Read the summary and the most important questions on Physiology: Cardiology

• 1 Lecture 1

• 1.1.1 General Function, Organization, Mechanisms of Circulation

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• Blood volume distribution

  70% contained in venous system (capacitance vessels)
  15% contained in heart and lungs
  10% contained in arteries (resistance vessels)
  5% contained in capillaries (Exchange vessels)

• Cross sectional area and velocity of blood flow

  Flow velocity steadily decreases going from aorta to capillaries, but it steadily increases going from capillaries to vena cava (changes in cross sectional area)
  
  This also allows the most exchange to take place in capillaries where: blood flows slowest, is exposed to greatest blood vessel surface area, and experiences the shortest diffusion distances.

• Mechanisms for venous return

  1. Some smooth muscle contraction
     
  2. Skeletal muscle contraction
  3. Respiratory inspiration
  4. Valves

• Pressures and resistances throughout the circulation

  Pump is pulsatile, and pressure fluctuates between 120 (SYSTOLE) and 80 (DIASTOLE) mmHg

• How does pressure change in each part of the vascular system: aorta->arteriole

  It falls progressively in each part, with little changes from aorta to arteries, with the major drop being in arterioles as the volume of blood within each vessel has decreased as they are divided amongst arterioles

• How does pressure change in each part of the vascular system: capillaries->veins

  Blood enters the capillaries at around 30 mmHg, leaves at 10 mmHg, and there is enough resistance in veins to arrive at almost 0 at right atrium

• 1.2 Stroke Volume and Cardiac Output

• Stroke Volume and Cardiac Output

  Filling pressure of the heart continually adjusted by contracting and relaxing smooth muscle in venous wall (venous return) 
  
  This allows for an appropriate Stroke Volume

• What is stroke volume?

  Volume of blood ejected from left ventricles by 1 beat of the heart (~30mL)

• What is cardiac output?

  The amount of blood circulated in 1 minute (L/min)

• 2 Lecture 2

• 2.1 Resistance = Pressure / Flow

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• What does resistance = DELTApressure / flow do?

  Determine resistance in systemic circulation (total peripheral resistance, TPR)