Chapter 9: Respiratory & Motor System

• Composition of air


  • 78% nitrogen
  • 21% oxygen
  • 1% carbon dioxide
  • Other gases
• Oxidation


  Process where oxygen breaks down organic compounds to gain energy
• Oxygen as final electron acceptor


  In the electron transport chain
• Humans can't live for more than a few minutes without enough oxygen
• The average adult uses 250 mL of oxygen every minute while resting
• Oxygen consumption may increase up to 20x during intense exercise
• Breathing (ventilation)


  The process of the exchange of air between the lungs and the environment, including inspiration and expiration
• Inspiration


  Moving O2 into the lungs
• Expiration

  Moving CO2 out of the lungs
• Respiration


  All processes involved in the exchange of oxygen and carbon dioxide between cells and the environment
• Respiratory Membrane


  • The membrane where the diffusion of oxygen and other gases occurs between the living cells of the body and the external environment
• Internal respiration


  Takes place within the body and involves the exchange of O2 and CO2 molecules between the blood and tissue fluids
• External respiration


  Takes place in the lungs and involves the exchange of O2 and CO2 molecules between the air and blood
• O2 concentration in cells is lower than in their environment since cells continuously use oxygen for cellular respiration; oxygen must constantly be replaced for cells to survive
• Components of the Human Respiratory System


  • Nasal cavities/Mouth
  • Pharynx
  • Epiglottis
  • Larynx
  • Trachea
  • Bronchi
  • Bronchiole
  • Alveoli
  • Diaphragm
• Nasal Cavities


  Air enters through the 2 nasal cavities (nostrils) or the mouth, where it is warmed and moistened, and foreign particles are filtered out
• Pharynx


  Air-filled channel at the back of the mouth, with two openings branching off: Trachea & Esophagus
• Trachea


  The windpipe, lined with mucus-producing cells and cilia that sweep debris up into the pharynx
• Epiglottis


  The structure covering the glottis (opening of the trachea) when swallowing, to prevent food/liquids from entering the respiratory tract
• Larynx


  The voice box, containing the vocal cords that vibrate as air passes over them
• Bronchi


  The passages from the trachea to the left and right lung, also containing cartilage bands
• Bronchioles


  The smallest passageways of the respiratory tract, without cartilage bands
• Alveoli


  Sacs of the lung in which gas exchange occurs, surrounded by capillaries
• Pleural Membrane


  A thin membrane that surrounds the outer surface of the lungs and lines the inner wall of the chest cavity, with fluid in between to reduce friction
• Breathing Movements


  Pressure differences between the atmosphere and chest (thoracic) cavity cause air to move in and out of the lungs
• Diaphragm


  A dome-shaped sheet of muscle that separates the organs of the thoracic cavity from those of the abdominal cavity, and can regulate the pressure in the chest cavity
• Inspiration


  Diaphragm contracts and pulls down, increasing chest volume and decreasing chest cavity pressure, causing air to move into the lungs
• Expiration


  Diaphragm relaxes and returns to its normal dome shape, decreasing chest volume and increasing chest cavity pressure, causing air to move out of the lungs
• Intercostal Muscles


  Muscles that raise and lower the rib cage, assisting the diaphragm in breathing movements
• Dalton's law of partial pressure


  Each gas in a mixture exerts its own pressure or partial pressure
• Diffusion of gas moves from an area of high partial pressure to low partial pressure
• The highest partial pressure of O2 is found in atmospheric air, therefore O2 will move from the air (pressure 21.2 kPa) into the lungs (pressure in alveoli: 13.3 kPa)
• The partial pressure of O2 is highest in the organs that carry large amounts of O2 and must transport O2 (trachea, alveoli, artery)
• Arteries carry O2 rich blood away from the heart, while veins carry O2 depleted blood back to the heart
• O2 never builds up inside cells, so there is a large change in the partial pressure of O2 between the arteries (12.6 kPa) and the capillaries (5.3 kPa), forcing O2 to diffuse into the tissues part of the capillaries
• CO2 is produced in cellular respiration and follows the opposite route, with the highest partial pressure in the tissues where it is produced
• Hemoglobin


  The oxygen-carrying molecule in red blood cells that greatly increases the blood's oxygen–carrying capacity
• Oxyhemoglobin


  Hemoglobin that is bound to oxygen
• The presence of oxyhemoglobin increases O2 carrying capacity of the blood by almost 70x
• The amount of O2 that combines with hemoglobin depends on partial pressure