Download Gas exchange

14 November 2012
Respiratory Physiology
Lab this week: EKGs and Blood Pressure.
Bring calculator and textbook to lab.
Wear clothes and shoes you can run in
comfortably.
Work on Hemorrhage Diagram!
1QQ 27 for 8:30
• Beginning with a loss of 1 liter of blood,
diagram the sequence of events that leads
to a change in the frequency of action
potentials in baroreceptors. (No
abbreviations allowed.)
1QQ 27 for 9:30
• Beginning with a loss of 1 liter of blood,
diagram the sequence of events that leads
to a change in the frequency of action
potentials in baroreceptors. (No
abbreviations allowed.)
• Respiration is the
overall movement
of gases between
the outside
environment and
the internal cells.
• Ventilation is the
movement of air
in and out of the
lungs.
O2
CO2
O2
CO2
• Ventilation should be
matched to
metabolism.
Carbon Dioxide reacts with water!
CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3Carbonic Acid
Bicarbonate
So disturbances in gas exchange or ventilation
are often associated with disruptions of pH.
pH changes with
Hypoventilation &
Hyperventilation
Gas Laws
Dalton’s Law
• Total pressure = sum of
partial pressures
• PATM = P N2 + P O2 + P CO2
• 100% = 79% + 21% + <1%
• P O2 = 0.21 x 760mmHg = 160
• Partial pressure of Oxygen in
atmosphere at sea level is
160 mmHg
• Regardless of elevation, air is
always 21% O2.
•
N2 is physiologically inert; ignore
except for decompression sickness
Henry’s Law
• Gases dissolve in liquids
in proportion to their
partial pressure in the air
in contact with that liquid
air
P O2 =160 mmHg
liquid
P O2 =160 mmHg
Why the difference in partial
pressures in Air and Alveoli?
Ventilation by Bulk Flow
Gas exchange by Diffusion
Where should the receptors be for
the negative feedback loop for
homeostasis?
Gas exchange
Gradient for CO2 is only 6 mmHg;
CO2 is more soluble and permeable than O2
Gas exchange
• All gases move by diffusion. Thus limited by:
– Surface area
– Distance
– Concentration (partial pressure) gradient
• In the lung, gases must move from air to water
and vice versa. The amount is proportional to
– Solubility (CO2 more soluble than O2)
– Temperature (colder fluids dissolve more gas)
– Pressure gradient
Respiratory
Physiology
The physics of
air flow
1) Flow in tubes
2) Ventilation
Poiseulle’s equation
The Structure underlying the function:
Upper
Respiratory
Tract
Lower
Respiratory
Tract
Intercostal muscles
Bronchitis= infection/inflammation of conducting airways
Asthma = smooth muscles contract →increase resistance to
airflow in conducting airways.
Pneumothorax (unilateral due to each lung having its own compartment.
Visceral pleura and parietal pleura
separated by fluid-filled pleural cavity which
allows lung and chest wall to slide relative
to each other but remain adhered unless air
enters the pleural cavity (which leads to
collapse of the lung and outward expansion
of chest wall on that side.)
Greg R. and the story of spontaneous pneumothorax
Upper Tract
Sleep Apnea
a)obstructive,
b)central
&
CPAP
Continuous Positive Airway Pressure