Cardiopulmonary Bypass, ECG, Pacemakers, Kidney Filtration, and More

Posted on Mar 8, 2025 in Biology

Heart-Lung Machine: Working Principle

A heart-lung machine, also known as a cardiopulmonary bypass (CPB) machine, is a medical device used to temporarily take over the functions of the heart and lungs during surgery. It is essential for complex cardiac procedures that require the heart to be stopped.

Working Principle:

  • Anticoagulation: The patient is given anticoagulant medication to prevent blood clots.
  • Cardiotomy: A surgical incision is made in the right atrium, and a cannula is inserted to drain deoxygenated blood.
  • Oxygenation and Perfusion: Deoxygenated blood is pumped through the machine. It is oxygenated in an artificial lung (oxygenator) and pumped back into the body through a cannula inserted into the aorta.
  • Cooling: To protect the brain and other organs, the patient’s body temperature is lowered using a heat exchanger in the machine.
  • Reperfusion: Once the procedure is complete, the machine is turned off, and the patient’s blood is reperfused to the heart and lungs.

Key Components:

  • Cannulas: Tubes connecting the patient’s blood vessels to the machine.
  • Pump: A mechanical pump that circulates the blood.
  • Oxygenator: A device that adds oxygen to the blood.
  • Heat Exchanger: A device that cools or warms the blood.
  • Reservoir: A container that holds the patient’s blood.

Brain as a CPU: Similarities and Differences

Similarities to a CPU:

  • Information Processing: Both process information. The brain receives sensory input, analyzes it, and generates outputs. A CPU processes data, performs calculations, and produces results.
  • Memory: The brain stores information (short-term, long-term, procedural). This is analogous to computer memory (RAM, ROM, hard drive).
  • Decision-Making: The brain makes decisions by weighing options and evaluating risks. Computers make decisions in a structured, deterministic manner.
  • Learning and Adaptation: The brain learns from experience. Computers can learn through machine learning algorithms.

Key Differences:

  • Biological vs. Digital: The brain is biological; the CPU is digital.
  • Parallel Processing: The brain can process multiple tasks simultaneously (parallel processing). Most CPUs are designed for sequential processing.
  • Emergent Properties: The brain’s capabilities arise from complex interactions. A CPU’s capabilities are determined by hardware and software.
  • Consciousness and Subjectivity: The brain has consciousness; a CPU does not.

ECG: Understanding Heart’s Electrical Activity

An ECG (Electrocardiogram) is a non-invasive test that records the heart’s electrical activity. It diagnoses heart conditions and monitors heart health.

Parts of an ECG:

An ECG tracing consists of waves and intervals representing the heart’s electrical cycle.

  • P wave: Atrial depolarization (atria contract).
  • QRS complex: Ventricular depolarization (ventricles contract).
  • T wave: Ventricular repolarization (ventricles recover).
  • PR interval: Time for the electrical impulse to travel from atria to ventricles.
  • QT interval: Total time for ventricles to contract and recover.
  • ST segment: Time between ventricular depolarization and repolarization.

Pacemakers: Types and Functions

Pacemakers are electronic devices implanted in the chest to regulate heart rhythm. They treat conditions like bradycardia (slow heart rate) or heart block.

Types of Pacemakers:

  • Single-chamber pacemakers: Stimulate one chamber, usually the right ventricle.
  • Dual-chamber pacemakers: Stimulate both atria and ventricles.
  • Biventricular pacemakers (CRT): Stimulate both ventricles and the left atrium; used for heart failure.
  • Leadless pacemakers: Small, implanted directly in the right ventricle.
  • Implantable cardioverter defibrillators (ICDs): Similar to pacemakers, but can deliver a shock to correct arrhythmias.

Kidney Filtration Mechanism

The kidney filters waste from blood. This occurs in nephrons, the kidney’s functional units.

The Filtration Process:

  • Glomerular Filtration:
    • Glomerulus: Network of blood vessels.
    • Bowman’s Capsule: Surrounds the glomerulus.
    • Filtrate: Blood plasma (minus large proteins) is filtered into Bowman’s Capsule.
  • Tubular Reabsorption:
    • Proximal Convoluted Tubule (PCT): Glucose, amino acids, water, and electrolytes are reabsorbed.
    • Loop of Henle: Concentrates urine; reabsorbs water and salts.
    • Distal Convoluted Tubule (DCT): Further reabsorption and secretion.
  • Tubular Secretion: Waste products (hydrogen ions, potassium ions, drugs) are secreted into the tubules.

Factors Affecting Filtration Rate:

  • Blood pressure
  • Glomerular filtration rate (GFR)
  • Hormones (aldosterone, ADH)

The Final Product: Urine

Urine is composed of water, urea, uric acid, creatinine, and electrolytes. It is collected and eliminated.

Spirometry: Assessing Lung Function

Spirometry is a non-invasive test to assess lung function. It measures inhaled/exhaled air volume and speed. It diagnoses lung diseases and monitors treatment.

Principles of Spirometry:

Measures lung volumes and flow rates using a spirometer.

Working of Spirometry:

  • Forced Vital Capacity (FVC): Deep breath, forceful exhale.
  • Forced Expiratory Volume in 1 second (FEV1): Air exhaled in the first second.
  • FEV1/FVC ratio: Indicates airflow efficiency.
  • Peak Expiratory Flow Rate (PEFR): Maximum exhalation speed.

Engineering Solutions for Parkinson’s Disease

Parkinson’s disease is a neurodegenerative disorder. Engineering solutions improve the quality of life.

  • Deep Brain Stimulation (DBS):

    Principle: Electrodes implanted in the brain deliver stimulation to modulate activity.

    Effectiveness: Reduces tremors, rigidity, and bradykinesia; improves daily activities.

  • Exoskeletons:

    Principle: Wearable robotic devices provide external support.

    Effectiveness: Assist with movement, improve balance, reduce fall risk.

  • Virtual Reality Therapy:

    Principle: VR simulates real-world environments for practice.

    Effectiveness: Improves motor function, balance, coordination; cognitive training.

  • Assistive Technology:

    Principle: Devices and systems (mobility aids, speech-to-text software).

    Effectiveness: Maintain independence, improve participation.

Architecture of Rods and Cones Cells

Rods and cones are photoreceptor cells in the retina, converting light into signals.

Rods:

  • Structure: Long, cylindrical; contain rhodopsin (light-sensitive pigment).
  • Function: Sensitive to low light; night vision; detect motion.

Cones:

  • Structure: Shorter, thicker; contain red, green, and blue opsins.
  • Function: Color vision; sensitive to bright light; perceive details.

Distribution: Cones are concentrated in the fovea (central vision). Rods are concentrated in the outer retina (peripheral vision).