Aquatic
animals typically use
gills, and much more metabolic energy is devoted to acquiring
oxygen.
Why?
Why is blood flow in the opposite
direction of water flow (i.e. counter
current)?
Why don't terrestrial organisms have
gills?
Not all terrestrial respiratory systems are the same. For
example:
Humans:
Human Lungs, two problems to
overcome:
1) Moving air
into lungs ->
PRESSURE
GRADIENT
Lungs
can be considered as two branched bags suspended in a sealed cavity.
When volume of a sealed container is
increased, what happens to pressure? How will air move along a
pressure gradient? What happens when volume is
decreased?
Lungs expand by contracting
(lowering)
diaphragm and
intercostal muscles along ribs.
Pathway of air flow:
2) Moving air
from lungs into blood -> DIFFUSION GRADIENT
atmospheric
pressure X concentration of a gas = partial pressure (the pressure exerted on a gas)
Do
humans go places where this equation becomes important?
Rate of diffusion is not only
influenced by partial pressure, but also the steepness of the diffusion
gradient. What is the end point of diffusion?
How does the body prevent equilibrium from
being
approached?
1. Air movement in lungs (discussed
above) maintains high concentration (partial pressure) of oxygen in
alveoli.
2. Blood circulation brings blood of low oxygen concentration to lungs (
Why is oxygen low as it enters the lungs?).
Two adaptations increase (steepen)
this concentration gradient:
- For oxygen, hemoglobin in red blood cells bind with
oxygen thus taking it out of
solution, lowering the blood concentration of oxygen (ideal
molecule - gives up
O2 when O2 low, pH low, or temp high)
- For carbon dioxide,
the enzyme carbonic
anhydrase speeds conversion
of carbon dioxide to carbonic acid, lowering the blood concentration of
carbon dioxide and maintaining the diffusion gradient.
Numerous respiratory problems have also been linked
to air
pollutants such as particulates, sulfer and
nitrogen oxides, hydrocarbons,
and ozone.
