Cardiovascular System Overview

Heart's Electrical System

  • Components: The heart's electrical system is essential for maintaining normal heart rhythm and function.

    • Sinoatrial Node (SA Node):

    • Located in the right atrium, it is the natural pacemaker of the heart. It generates electrical impulses that initiate heartbeats.

    • Controls the heart rate by determining the rhythm of the heart.

    • Internodal Tracks:

    • Pathways that conduct impulses from the SA Node to the Atrioventricular Node.

    • Includes three main pathways:

      • Anterior Internodal Track
      • Middle Internodal Track
      • Posterior Internodal Track

    • Atrioventricular Node (AV Node):

    • Located at the junction of the atria and ventricles.

    • Receives impulses from the SA Node and serves as a gatekeeper, slowing down the impulse before sending it to the ventricles, which allows for optimal filling of the heart chambers.

    • Bundle of His:

    • A collection of heart muscle cells specialized for electrical conduction.

    • Conducts impulses from the AV Node into the right and left bundle branches.

    • Purkinje Fibers:

    • Network of fibers that spread throughout the ventricles, conducting impulses efficiently, and leading to synchronized ventricular contraction.

Blood Pressure Categories

  • Blood Pressure Readings: Measured in mm Hg (millimeters of mercury), blood pressure is categorized as follows:

    • Normal:

    • Systolic: < 120

    • Diastolic: < 80

    • Elevated:

    • Systolic: 120-129

    • Diastolic: < 80

    • Hypertension Stage 1:

    • Systolic: 130-139

    • Diastolic: 80-89

    • Hypertension Stage 2:

    • Systolic: ≥ 140

    • Diastolic: ≥ 90

    • Hypertensive Crisis:

    • Systolic: > 180

    • Diastolic: > 120

  • Source: Information is based on guidelines from the American Heart Association.

Antihypertensive Therapy

  • Classifications: Antihypertensive medications are classified into several categories based on their mechanism of action:

    • Diuretics:

    • Medications that help the body eliminate excess fluid and sodium, leading to a decrease in blood volume and, subsequently, blood pressure.

    • Adrenergic Blockers:

    • Medications that inhibit the activity of adrenalin and noradrenaline on the heart and blood vessels, which helps relax blood vessels and lowers heart rate.

    • Vasodilators:

    • Medications that directly relax blood vessels, causing them to widen and therefore reduce blood pressure.

    • Angiotensin-converting enzyme (ACE) Inhibitors:

    • Medications that inhibit the enzyme ACE, which decreases levels of angiotensin II, a substance that narrows blood vessels. This helps lower blood pressure and reduce strain on the heart.