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7 Cards in this Set

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  • Back
What molecule does CO2 form in the body?
Carbonic Acid
H2CO3 <> H+ + HCO3-
This is the Henderson-Hasselbach Equation.
PCO2 goes down from hypoventilation, so the kidneys pee out bicarb
What are some conditions that affect your Acid-Base balance?
Acidosis is a Left shift of the curve.
Alkalosis is a Right shift of the curve.
Ketone bodies neutralize your bicarb so you become acidotic. Basically Diabetics do not have insulin to take advantage of glucose so they start using protein for energy... the biproduct of protein metabolism is ketones. Ketones neutralize bicarb, making you acidotic.
-Vomiting/Bulemia: loss of CL- so kidneys hold on to bicarb causing a 'Hypochloremic Metabolic Alkalosis'
-Hyperventilating: for too long the level of ionized Ca goes down, trigerring muscle spasms, tetany.
What are four points to be made about the control mechanisms of the brain?
1. In the brain stem the Pons and Medulla are the centers for controlling respirations.
2. The medulla is seperated into a dorsal group that trigger inspiration, and a ventral group that are associated with expiration. During normal breathing since expiration is passive, there's no firing. But duing active expiration the ventral group of the medulla is firing. If your bodies is alkalotic then the medulla will fire less... slowing breathing to not worsen the alkalosis.
3. Cortex breathing is under voluntary control. Intentional hyperventilation can cause CO2 to drop by half.
4. Other parts of the brain can control respirations. For example, rage and fear can effect respirations.
What are the different types of chemoreceptors that sense changes in blood values related to ventilation?
1. Central Chemoreceptors are located near the ventral surface of the medulla, and are surrounded by brain extracellular fluid and respond to changes in its H+ concentration. CSF plays an important role. When blood pCO2 rises, CO2 diffuses into CSF, liiberating H ions, which stimulate chemoreceptors. The resulting hyperventilation reduces pCO2 in blood and CSF. They are not sensitive to changes in PO2 of blood.
2. Peripheral chemoreceptors are located in the carotid bodies at the bifurcation of the common carotid a.'s, and in the aortic bodies above and below the aortic arch. These chemoreceptors respond to DECREASES in arterial PO2 and pH, and INCREASES in arterial pCO2.
These receptors respond to both hypoxia and changes in CO2, but more prominantely to hypoxia.
Little response until pO2 goes below 100 mmHg. They respond to arterial instead of venous blood and the response is rapid.
pO2 of 60 mmHg means that 80% of Hgb are saturated.
ALSO, there are lung receptors:
1. Pulmonary Stretch Receptors: The Hering Brauer Reflex.
2. Irritant Receptors - ^RR to get rid of irritant.
3. J receptors (juxta capillary receptors)
4. Bronchial C fibers
What are the chemoreceptors sensetive to? When is hypoxemia important in respiratory control?
PCO2 is what chemoreceptors respond most to. Most of the response comes from central chemoreceptors, but peripheral contributes and their response is quicker.
The response to increase CO2 is magnified if O2 is decreased.
Only the peripheral chemoreceptors are involved in hypoxemia.
O2 becomes important at high altitudes, and patients with lung disease that have CO2 retention. These patients rely on pO2 to control their respiratory drive, b/c they are disensitized to hypercarbia. So don't give a lung disease patient with CO2 retention a 100% O2, b/c they'll lose their respiratory drive!
When do patients get hypoxemia?
severe hypoxemia
high altitudes
during deep sleep
brain injury
What is FEV or FEV1? What is the FEV1/FVC ratio?
FEV stands for Forced Expiratory Volume.
FEV - the volume of gas exhaled by a forced expiration after a full inspiration in 1 second.
Vital Capacity - total volume of gas exhaled after a full inspiration.
Forced Vital Capacity - used to indicate that expiration is forced. May be slightly less than vital capacity. Don't force it, baby!
The ratio of FEV1 to FVC gives valuable information, by indicating the fraction of forced vital capacity that is exhaled in the first breath.
Normal FEV1/FVC >/= 75%