Nursing Pharmacology:  Introduction to Autonomic Pharmacology

Choose the correct answer for each question.

Preload & Contractility

Myocardial Function


  •  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  Pressure Peripheral resistance:

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