The Mechanism of Breathing

• What is the mechanism of breathing primarily concerned with?

  Bringing oxygen and removing carbon dioxide
• What happens during inspiration?

  External intercostal muscles contract, diaphragm lowers
• What occurs during expiration?

  Internal intercostal muscles contract, diaphragm relaxes
• What do external intercostal muscles do during inspiration?

  They contract and pull ribs upwards and outwards
• What do internal intercostal muscles do during expiration?

  They contract and move ribs downwards
• How does the diaphragm change during inspiration?

  It contracts and moves downwards
• What happens to thorax volume during inspiration?

  It increases
• What is the effect of increased thorax volume on air pressure in the lungs?

  It reduces air pressure within the lungs
• What happens to air movement when lung pressure decreases?

  Air moves into the lungs
• What is pulmonary ventilation?

  Movement of air in and out of lungs
• How is pulmonary ventilation calculated?

  Tidal volume x breathing rate
• What is tidal volume?

  Volume of air in each breath at rest
• What is breathing rate?

  Number of breaths in one minute
• What is the role of the diaphragm?

  Separates thorax from abdomen and aids breathing
• How do intercostal muscles contribute to breathing?

  They control rib movement during inspiration and expiration
• What happens to thorax pressure during expiration?

  It increases
• What is the pressure gradient during inspiration?

  Atmospheric pressure is greater than lung pressure
• What is the pressure gradient during expiration?

  Lung pressure is greater than atmospheric pressure
• How do the diaphragm and intercostal muscles work together during breathing?

  They coordinate to change thorax volume and pressure
• What happens to the rib cage during expiration?

  It moves downwards and inwards
• What is the effect of decreased thorax volume on lung pressure?

  It increases air pressure within the lungs
• What is the purpose of ventilation?

  To maintain diffusion gradients across alveoli
• How does air move into the lungs during inspiration?

  Air is forced in due to pressure gradient
• How does air move out of the lungs during expiration?

  Air is forced out due to pressure gradient
• What muscles control the pressure changes during breathing?

  Diaphragm and intercostal muscles
• Where is the diaphragm located?

  Between the thorax and abdomen
• What happens to the diaphragm during expiration?

  It relaxes and returns to domed position
• What is the role of external intercostal muscles during inspiration?

  They contract to pull ribs upwards and outwards
• What is the role of internal intercostal muscles during expiration?

  They contract to move ribs downwards
• How do breathing rates affect pulmonary ventilation?

  Higher rates increase pulmonary ventilation
• If a person has a tidal volume of $0.5 \text{ dm}^3$ and a breathing rate of $12 \text{ min}^{-1}$, what is their pulmonary ventilation rate?


  $6 \text{ dm}^3 \text{ min}^{-1}$
• If a person has a pulmonary ventilation rate of $10.2 \text{ dm}^3 \text{ min}^{-1}$ and a tidal volume of $0.6 \text{ dm}^3$, how do you calculate the breathing rate?


  Breathing rate = pulmonary ventilation / tidal volume
• What is the purpose of maintaining diffusion gradients across the alveolar epithelium?

  To facilitate gas exchange
• What is the specific name for breathing in?

  Inspiration (inhalation)
• What is the specific name for breathing out?

  Expiration (exhalation)
• How do the diaphragm and intercostal muscles work together during breathing?

  They coordinate to change thorax volume and pressure
• What happens to the rib cage during expiration?

  It moves downwards and inwards
• What is the effect of decreased thorax volume on lung pressure?

  It increases air pressure within the lungs
• What is the purpose of ventilation?

  To maintain diffusion gradients across alveoli
• How does air move into the lungs during inspiration?

  Air is forced in due to pressure gradient