22. Respiration Flashcards
What is ventilation?
Movement of the medium (air, water) over a gas exchange surfaces
What does respiration refer to?
- Oxidation of the end products of glycolysis (by 02 in eukaryotes)
- Breathing or physiological respiration
Is it better to breathe from oxygen in water or air?
- There is 21% O2 in the atmosphere
- Atmospheric pressure changes with altitude, higher the altitude the lower the pressure
- Fewer molecules of oxygen/ litre air
- In still water water is not in contact with air and contains less O2
What is hypoxia?
- Low O2 in blood or environment
What is anoxia?
- Complete absence of O2 in the environment
What is hypercapnia?
Excessively high CO2 levels in blood
What is partial pressure in reference to gas?
Component of total pressure contributed by a single (free) gas within a mixture of gases
Why is air a better respiratory medium than water?
- Oxygen diffuses 8000 times more rapidly in air than in water
- To move medium over a gas exchange site, more energy is required to mover water than air (water is 800x denser and 50x more viscous than air)
How does respiration occur in small animals?
- Small animals can take up 02 directly from the environment through the body surface
- Simple diffusion distributes 02 throughout the body, into cells and throughout their cytoplasm
- No specialised respiratory structures required
When is diffusional transport of 02 effective?
Diffusional transport of 02 is only efficient if distance is 1mm at most
What are the greater demands for the respiratory system in larger more complex animals?
- Higher cellular metabolic rate
- Reduction in total surface area available for gas exchange
- Large, multicellular organisms are too large for diffusion
Thus both aquatic and terrestrial animals have evolved respiratory systems with a large surface area to maintain adequate respiratory supply of oxygen to their tissues
What is Fick’s law?
Rate of gas exchange = (surface area x concentration gradient x diffusion coefficient)/diffusion distance
How is gas exchange maximised (based on the equation?
- Increase surface area
- Increase pressure difference
- decrease diffusion distance
If terrestrial animals breath air then why does solubility of gases matter?
- Matters because it is moist within the lungs so gases must dissolve through a layer of fluid to get into the lungs, and must stay dissolved when they are in the blood
What characteristics does an exchange site have?
- A large surface area
- Small diffusion distance (i.e thin epithelium/endothelium) between the respiratory medium and the blood or blood and tissues
- A highly vascularised respiratory surface
Where do respiratory gases diffuse?
Across the exchange site (the respiratory epithelium and capillary endothelium)
How do you increase transport of O2 to tissues?
High surface area to volume ratio, ensure surfaces are thin and highly vascularised with lots of blood vessels
What is the purpose of a ventilation system?
- It is to keep a constant supply to medium moving across the respiratory exchange site
- Improves rate of gas exchange
- Ensures that fresh supplies of O2 rich medium are supplies to the exchange surface
What is the structure of the ventilation system in fish?
Mouth and operculum allow unidirection flow of water across gills
What is the structure of the ventilation system in frogs?
Buccal cavity (2 phases of lung ventilation, tidal flow of air)
What is the purpose of air sacs?
System for two cycles of inhalation and exhalation (unidirectional air flow)
What is the purpose of the internal transport (circulatory system)?
- It moves the dissolved O2 from the exchange site to respiring tissues
- Also transports CO2 away from the metabolising tissues
Why is the internal transport (circulatory) system essential?
Because diffusion is exceedingly slow over even moderate distances.
What is the purpose of the circulatory system?
The heart acts as a pump to increase the movement of blood around the body
