Introduction to Autonomic Pharmacology

Choose the correct answer for each question.

Preload & Contractility

Preload & Contractility


  •  As blood volume returning to the heart
    increases, preload increases and there is enhanced
    filling with ventricular dilation.
        

  • According to Starling's Law, increased
    ventricular stretch usually leads to increased
    contractility.
    Increased preload and
    increased contractility lead to increased stroke volume
    and ultimately an increase in arterial pressure, all
    other factors remaining equal.    

  •   Some antihypertensive drugs decrease
    preload.

  • Heart rate: Since the product of heart rate and
    stroke volume equals cardiac output, an increase in heart
    rate will increase arterial blood pressure, all other
    factors remaining equal.

  • Some antihypertensive agents decrease heart rate
    (ß-adrenergic receptor antagonists, e.g.).

  • Recall: Heart Rate X Stroke Volume = Cardiac
    Output
  • Cardiac Output X Peripheral Resistance = Arterial
    PressurePeripheral resistance:

  • For a given cardiac output, blood pressure
    depends only on peripheral resistance. Some
    antihypertensive drugs act to reduce peripheral
    resistance.

 
Adrenergic Drugs; Antihypertensive Medications and Mechanisms