Physiology 1 Flashcards
What is Internal Respiration?
Internal respiration refers to the intracellular mechanisms which consumes O2 and produces CO2 (at cell level)
What is External Respiration?
The sequence of events leading to exchange of O2 and CO2 between external environment and body cells
How many steps does external respiration involve?
4 steps
Step 1 of external respiration
Ventilation - gas exchange between atmosphere and alveoli in the lungs
Step 2 of external respiration
Exchange of O2 and CO2 between air in alveoli and blood in the lungs
Step 3 of external respiration
Transport of O2 and CO2 between lungs and tissue via the blood stream
Step 4 of external respiration
Exchange of O2 and CO2 between blood and tissue
Leads to internal respiration occurring at cellular level
Route of oxygen through external and internal respiration
Atmosphere > alveoli of lungs > heart > bloodstream > tissue > cells
Route of CO2 through internal and external respiration
Cells > tissue > bloodstream > heart > alveoli of lungs > atmosphere
What 4 body systems are involved in external respiration?
Respiratory system
Cardiovascular system
Haematology system
Nervous system
What does Boyle’s Law state?
Pressure exerted by a gas varies inversely (opposite manner) with the volume of the gas at any constant temperature
According to Boyle’s Law, what happens to the gas pressure when the volume of gas is increased?
As gas volume increases, the pressure exerted by gas decreases
What causes the thorax and lungs to expand?
Contraction of inspiration muscles
What two forces hold the thoracic wall and the lungs in close opposition?
(1) intrapleural fluid cohesiveness - water molecules attached together
(2) negative (relative to atmosphere) intrapleural pressure - sub-atmospheric intrapleural pressure creates pressure gradient across lung and chest wall
The intrapleural cavity has a _______ (_______) pressure relative to the atmosphere and lung/alveoli (760 mm Hg)
Lower (756 mmHg)
The three pressures important in ventilation
Atmospheric pressure
Intra-alveolar (intrapulmonary) pressure
Intrapleural (intrathoracic) pressure
Atmospheric pressure is pressure caused by…
weight of gas in the atmosphere (760mmHg)
Intrapleural-alveolar pressure is pressure…
within lung alveoli (760mmHg) when in equilibrium with atmospheric pressure
Intrapleural (intrathoracic) pressure is pressure exerted …
outside lungs within pleural cavity (756mmHg) always less than atmosphere pressure
Inspiration is an _______ process depending on ___________
Inspiration is an active process depending on muscle contraction (diaphragm and intercostal muscles)
What effect does the increased size of the lungs have on intra-alveolar pressure?
Intra-alveolar pressure falls (759mmHg) - (air molecules less condensed - Boyle’s law), allows air to enter lungs down pressure gradient
Expiration is a ________ process brought about by ___________
Expiration is a passive process brought about by relaxation of inspiration muscles
Recoil of lungs causes…
Intra-alveolar pressure to rise (761mmHg) - (air molecules condensed) air then exists down its pressure gradient
What is pneumothorax and what does it indicate?
When there’s air in the pleural space (abnormal), indicates hole in lung and leads to lungs collapsing
