Systems Physiology Lecture 9: Respiration

Systems Physiology Lecture 9: Respiration

• The lecture covers the function of the respiratory system's components, respiration as a mechatronic system, and how biomedical devices assess and treat respiratory functions.
• Key objectives for the lecture include explaining the function of different parts of the respiratory system, describing respiration as a mechatronic system, and identifying how biomedical devices assess and treat respiratory functions.
• The respiratory system comprises the nose, pharynx, larynx, trachea, bronchi, and bronchioles. These structures form the conducting zone and the lower respiratory tract. The sinuses, throat, and larynx are also part of the upper respiratory tract. The lungs are crucial for gas exchange.
• The external nostrils are for air intake. The nasal chamber filters, warms, and humidifies the air. The pharynx is a passageway for both air and food, and the larynx houses the vocal cords. The epligottis prevents food from entering the windpipe.
• The trachea is a long tube passing through the mid-thoracic cavity and divides into left and right bronchi. Bronchi further divide into bronchioles. Bronchioles terminate in alveoli (balloon-like structures).
• The lungs are a pair of sac-like structures, covered in the pleura. The major function of the respiratory system is to oxygenate blood and expel carbon dioxide. Oxygenated blood is sent to the heart and deoxygenated blood to the lungs.
• Key components of the system include lungs, diaphragm, intercostal muscles, airways (trachea, bronchi, bronchioles), and the nervous system for neural control. The lungs are the primary gas exchange organ, and the diaphragm and intercostal muscles mechanically control breathing.
• The airways conduct air to and from the lungs. The brain stem—specifically the medulla oblongata and pons—controls breathing patterns and rates based on sensory information.
• Respiration is a bio-mechatronic system with mechanical analogues. The thoracic cavity acts like a piston-cylinder system in changing volume to create pressure gradients for air movement; the recoil and compliance of lung tissue are analogous to mechanical springs.
• Thoracic movement can be assessed by measuring lung volumes and capacities. These can be done with spirometers, pulse oximeters, and blood gas analyzers.
• The system has sensory components such as chemoreceptors (detecting oxygen, carbon dioxide, and pH levels) and mechanoreceptors (detecting stretch and pressure changes).
• The central nervous system acts as a microcontroller for breathing, integrating sensory data to change output to respiratory muscles to maintain homeostasis. These control breathing rates, adapting to metabolic needs and the environment. The medulla oblongata and pons coordinate rhythmic breathing. Peripheral and central chemoreceptors adjust breathing by monitoring CO2, O2, and pH levels in the blood and cerebrospinal fluid.
• Breathing mechanics involve coordinated interactions among muscles, bones, and lung structures to facilitate gas exchange. The physical process of breathing has inhalation (inspiration) and exhalation (expiration) phases, which require muscle contraction to change the volume of the thoracic cavity to control pressure.
• The inhalation phase involves the diaphragm moving downward, increasing the chest cavity's vertical dimension, and the external intercostal muscles expanding the ribcage. The expansion causes a decrease in intrapulmonary pressure compared to atmospheric pressure that forces air into the lungs. Accessory muscles can help with deeper breathing.
• Exhalation requires the relaxation of the diaphragm and external intercostal muscles, allowing the ribcage to return to its original position and the lungs to recoil. This increases intrapulmonary pressure, forcing air out. Abdominal muscles aid in forceful exhalation.
• Mechanical components like compliance (the ease of lung expansion), airway resistance, and surface tension (reduced by surfactant) affect breathing. Elasticity of the lung allows it to return to a resting state during exhalation.
• Alveolar structures and surfactant are essential for gas exchange. Alveoli are small air sacs in the lungs with thin walls, maximizing surface area for gas exchange. Pulmonary surfactant reduces surface tension, preventing lung collapse.
• Partial pressure gradients drive gas diffusion (Fick's Law) between alveoli and capillaries. Oxygen diffusion occurs from alveoli to blood, and carbon dioxide from blood to alveoli due to pressure differences.
• Hemoglobin in red blood cells transports oxygen, binding to and carrying oxygen molecules, and hemoglobin dissociation curves illustrate the relationship between oxygen saturation and partial pressure.
• Respiratory volumes and capacities (tidal volume, vital capacity, residual volume, and total lung capacity) describe the amount of air inhaled/exhaled.
• Medical devices like spirometers, pulse oximeters, and blood gas analyzers assess respiratory function by measuring lung volumes and capacities, blood oxygen saturation, and arterial blood gases (oxygen/carbon dioxide/pH).
• Students are assigned to present on how wearable sensors, mobile apps, or devices assess human physiology for different purposes including bodily function, proposing one enhancement feature.