Cardiovascular System: Physiology, Adaptations, and Function

Posted on Mar 28, 2025 in Biology

Altitude Adaptations and Blood

  1. Altitude and Oxygen: With increasing altitude, atmospheric pressure decreases, resulting in less oxygen availability. This leads to lower oxygen pressure in the blood (hypoxemia), causing difficulty in breathing. Adaptive mechanisms to compensate for this include:
    • Hyperventilation
    • Polycythemia
  2. Blood Analysis at High Altitudes: Individuals who have lived at high altitudes for years exhibit increased hematocrit and higher amounts of hemoglobin in their blood.
  3. Red Blood Cells: Inhabitants of high altitudes (above 4,000 meters) have nearly twice as many red blood cells as those in central valleys. This is likely due to the lower atmospheric pressure in the Andes, requiring more red blood cells to maintain adequate oxygen transport.

Heart Function and Electrical Activity

  1. Heart’s Electrical Activity: Electrical activity in the heart begins on the wall of the right atrium.
  2. Cardiac Output and Venous Return: Cardiac output (the amount of blood ejected per minute) and venous return (the amount of blood returning to the heart) must be equal to maintain a balance in the filling of the heart with each cycle.
  3. Arteriolar Contraction: During strenuous effort, the body adjusts by contracting some arteriolar territories to bypass blood to areas with increased demand, increasing oxygen availability in tissues.
  4. Atrial Systole: Atrial systole occurs slightly before ventricular systole (0.1 seconds) to allow complete filling of the ventricles and ensure unidirectional blood flow.
  5. Diastole: During diastole (relaxation of the heart muscle), arteries maintain blood flow by accumulating pressure after ventricular systole.

Blood Components and Properties

  1. Blood Clotting: When blood is placed in a test tube, it forms a clot, leaving serum behind.
  2. Pulmonary Artery: The only artery that carries blood loaded with carbon dioxide is the pulmonary artery.

Heart Diseases and Diagnostics

  1. Atrial Fibrillation: Acute heart diseases, such as atrial fibrillation, can alter the synchronized movements of the atrial myocardium. This condition features spontaneous generation of action potentials in the atria and can be detected by alterations in the P wave on an EKG.
  2. EKG: An EKG is a non-invasive test used for:
    • Detection of heart attacks
    • Diagnosis of heart arrhythmias

Vascular System

  1. Capillaries: The vascular region with the largest total cross-sectional area in the body is the capillaries. The presence of capillaries results in a decrease in blood speed and facilitates substance exchange.
  2. Veins vs. Arteries: Veins have thinner walls than arteries because they carry less blood per minute.

Heart Valves and Sounds

  1. Bicuspid Valve: The bicuspid valve, also known as the mitral valve, is located between the left atrium and ventricle and has two membranes.
  2. Heart Sounds: The second heart sound is caused by the closure of the aortic and pulmonary valves.

Pulse

The pulse is the number of heartbeats in a minute, which can be measured at the radial, carotid, or aorta arteries.

EKG Wave Interpretation

  • P Wave: Indicates atrial contraction to pump out blood.
  • QRS Complex: Indicates ventricular contraction to pump out blood.
  • ST Segment: Indicates the time elapsed from the end of ventricular contraction until the rest period begins.
  • T Wave: Indicates the rest period of the ventricles.

Blood Composition

Blood returning to the heart from the body has a greater amount of carbon dioxide compared to blood leaving the heart.