Lec 19- Gas Exchange Mechanisms Flashcards
Partial Pressure
is pressure that a particular gas in a mixture exerts independently.
Nitrogen narcosis
Under hyperbaric conditions takes more than hour for dangerous amounts to accumulate.
Resembles alcohol intoxication.
Decompression sickness
Occurs as bubbles of nitrogen gas form in tissues and enter blood, blocking small blood vessel and producing “bends”.
Hb - hemoglobin
Transports O2
Heme groups
4 in Hb. Carries 4 O2.
Fe - iron
The portion of a heme group that attracts the O2.
Oxyhemoglobin
When oxygen in bound to Hemoblobin
Methemoglobin
Contains ferric iron (Fe3+) - the oxidized form.
Lacks electron to bind with O2.
Blood normally contains a small amount.
Carboxyhemoglobin
Heme combined with carbon monoxide.
Carbon Monoxide
CO.
Hb has a higher affinity for CO than O2.
Oxyhemoglobin dissociation curve
Shows a graph of how affinity decreases when pH decreases.
BPG/D-2,3-biphosphoglycerate AKA DPG/2,3-diphosphoglycerate
Affect the ability of Hb to bind to O2.
Fetal hemoglobin
has 2 y-chains in place of B-chains of HbA.
Sickle-cell anemia
HbS has valine subsituted for glutamic acid at 1 site on B chains. At low PO2, HbS crosslinks to form a “paracrystalline gel” inside RBC’s. Makes RBC’s less flexible and more fragile.
Myoglobin
Red pigment found exclusively in striated muscle.
Slow-twitch skeletal and cardiac muscle fibers are rich in myoglobin.
Carbaminohemoglobin
20% of CO2 transported in blood.
Carbonic Acid
…
Bicarbonate ion
70% of CO2 transported in blood.
CA - carbonic anhydrase
In RBC’s this catalyzes formation of H2CO3 from CO2 and H2O
Chloride shift
In tissues.
Cl- enters the RBC; HCO3- leaves. Plays role in CO2 coming into RBC.
Reverse chloride shift
In lungs.
Cl- leaves the RBC; HCO3- enters. Plays role in CO2 entering alveoli.
Most important buffer in blood?
Bicarbonate
Volatile acid
One of the 2 major classes of acids in body.
Can be converted to a gas.
Non-volatile acid
All other acids are nonvolatile and cannot leave the blood.
e.g. lactic acid, fatty acids, ketone bodies.
Respiratory acidosis
Acidosis resulting from abnormal retention of CO2 arising from hypoventilation
Respiratory alkalosis
Alkalosis caused by excessive loss of CO2 from the body as a result of hyperventilation
Metabolic acidosis
Acidosis resulting from any cause other than excess accumulation of carbonic acid in the body.
Metabolic alkalosis
Alkalosis caused by a relative deficiency of noncarbonic acid.
Rhythmicity center
FIND
Chemoreceptors
Receptors that respond to a specific chemical
Central chemoreceptor
Sensituve to changes of PCO2.
Located in the medulla.
Peripheral chemoreceptor
Monitors atrial PO2.
Includes the carotid bodies and aortic acids.
Aortic bodies
Peripheral chemorecptor located on the aorta.
Carotid bodies
Peripheral chemorecptor located on the carotid artery.
Hypocapnia
Caused by hyperventialtion.
Below normal CO2 in the arterial blood.
Hypercapnia
Cause by hypoventilation.
Excess CO2 in the aterial blood.
Hypoxemia
Abnormally low levels of O2 in the blood.
