topic 10 powerpoint 10.2 Flashcards
What are the two control mechanisms of breathing?
- regulation centers in the brain stem
2.local chemical controls
What two things are skeletal muscle?
intercostal muscles and diaphragm
What will stimulate intercostal muscles and diaphragm to contract?
motor nerves
How is inspiration initiated?
a burst of action potentials in spinal motor neurons to the inspiratory muscles like the diaphragm
*opposite for elastic lung recoil
During quiet breathing
During quiet breathing, there is little or no muscle contraction or relaxation involved in expiration. This means that the muscles involved in breathing, such as the diaphragm and intercostal muscles, do not actively contract or relax to exhale air. Instead, expiration occurs passively as the elastic lungs recoil after inhalation.
What controls nerve impulses to the respiratory muscles
so that they can be alternately increased and decreased?
The neurons in the respiratory centers of medulla oblongata in the brainstem
aka medullary respiratory center
medullary respiratory center contains who two groups of neurons?
DRG: Dorsal respiratory group
VRG: Ventral respiratory group
In DRG, how are its function carried out
-primarily fire during inspiration
-stimulate diaphragm
*phrenic+ intercostal nerves activate muscles involved in inspiration, innervate diaphragm
In VRG, how are its function carried out
active during inspiration and expiration, by
stimulates forceful exhalation by increasing signals stimulating inhalation
What is the Pre-Botzinger complex?
Pacemaker cells and other specialized neurons in the upper part of the VRG is believed to comprise the respiratory rhythm generator
Explain how signals are send to brain and then AP are fired
1.peripheral chemoreceptors[carotid/aortic bodies] detect changes in CO2 levels and send to medulla
2.in medulla, central chemoreceptors send signals to meduallary neurons
3.Control centers in medulla (and pons) adjust rate and depth of
breathing to compensate for changes in blood gases
Peripheral chemoreceptors
respond to changes in arterial blood
[Arterial blood refers to the oxygenated blood .]
Stimulated by:
1. Decreased Po2 (hypoxia)
2. Increased H+ (metabolic acidosis)
3. Increased Pco2 (respiratory acidosis)
Central Chemoreceptors:
respond to changes in brain extracellular fluid
Stimulated by increased CO2 via changes in H+ concentration
What equation is used to understand central chemoreceptors?
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
Local controls aim to keep ventilation and perfusion rates consistent. How does it do that when O2 levels drop?
- rate of airflow into the lungs is less than the rate of blood flow through the capillaries surrounding the alveoli, O2 drop
2.Smooth muscles in the walls of lung arterioles contract, reduces blood flow
3.More time for blood to pick up O2
Diffusion of gases occur through what mechanism?
differences in partial pressure
Ex:O2 is higher in alveolar air than in the
blood in the capillary networks surrounding the alveoli, thus: O2 diffuses from alveolar air into blood
What is partial pressure?
pressure of each individual gas in a
mixture; determined by its proportion/concentration in the mixture.
Ex: So, if a gas has a higher concentration, it will contribute more to the total pressure of the mixture
What is Dalton law?
Partial Pressure of Gas in a Mixture is
Independent of Other Gases in the Mixture
Moisture in lung causes partial
pressure of O2 to be reduced
(~100mmHg)
Therefore, the partial pressure of oxygen at sea level is approximately
PO2 dry inhaled air
160 mm Hg.
PCO2 of expired air is
27mmHg
PO2 of expired air is
120mmHg
Why might expired air be high in oxygen?
Thus, we only expel a fraction of the air in our lungs since some air is in the dead space
expired air percentage of CO2 and O2
15.7% O2
3.6% CO2
pulmonary arteries
PCO2 and PO2
PCO2 46
PO2 40
Pulmonary veins
PCO2 and PO2
PCO2 40
PO2 100
Alveolar sacs
PCO2 and PO2
PCO2 40
PO2 100
Start of veins in body tissues
PCO2 and PO2
PCO2 46
PO2 40
What creates a partial pressure gradient between O2 in alveolar air
and in blood? (lungs)
large quantities, one hemoglobin combines with 4 O2molecules
Start of capillaries entering body tissue
PCO2 and PO2
PCO2 40
PO2 100
where does oxygen bind to in hemoglobin?
4 heme (Fe) groups that can reversibly bind with an O2 molecule
How does O2 relate to the saturation of Hb?
Hb + O2 -> HbO2
How does cooperativity relate to Hb?
one o2 binds to Hb, conformational change to allow other O2 to bind to it
Hb carries oxygen, how might that oxygen be released into the tissue?
HbO2 -> Hb + O2
HbO2 -> Hb + O2
Why is PO2 is lower in tissue than blood because?
As oxygen is used up by the cells, the concentration of oxygen decreases in the tissue, leading to a lower partial pressure. This creates a concentration gradient that favors the release of more oxygen from hemoglobin in the blood. The lower partial pressure in the tissues allows oxygen to diffuse from the blood into the cells where it is needed for cellular respiration.
HbO2 -> Hb + O2
affinity of Hb for O2 is decreased by
Increase in CO2
-can bind to Hb and facilate release of O2
Drop in pH
-increase in CO2/ lactic acid
-The reduction in
binding affinity at lower pH increases the amount of O2 released in
active tissues
Increase in temperature
-higher heat, reduces affinity to O2
*exercising
Factors produced by active tissues affect the affinity of hemoglobin for oxygen
How would a Hemoglobin saturation level in lungs look like as a graph?
In alveoli, when air comes inside the lungs, partial pressure of O2 is high because there is a lot of it, based on Hb + O2 -> HbO2, which means oxygen saturation is high.
100mg Hg, 100% saturation, ph 7.4
Happens at systemic arterial ^^
In body tissues, 40 mg Hg and 80% saturation
^Venous partial pressure of O2
Saturation of hemoglobin just starts to drop when…
drop of partial pressure of oxygen in blood from about
100mmHg to about 60mmHg
venous partial pressure of O2 is what
blood returning from tissues, that can contains leftover o2
What is a reserve?
venous partial pressure of O2, 80% saturation, still have more oxygen that hemoglobin can give up in tissue
What mmHg do we see large decrease in saturation of O2 in HB
From about 0-50mmHg, a small change in PO2 can cause a significant amount O2 to be released from hemoglobin.
Describe pathway of CO2
1)cellular oxidation in active tissues,
diffuses from cells to interstitial fluid to blood plasma, pCO2 is higher in tissues than in blood
2)in lungs, partial pressure of CO2 is higher in blood than in alveolar air
CO2 is released from blood into the alveolar air
Partial pressure of CO2 is higher in
tissues than in blood
SOme ways CO2 is transferred?
About 10% of CO2 dissolves in blood plasma
70% is converted into H+ and HCO3- (bicarbonate) ions
H+ combine with hemoglobin or proteins
20% combines with hemoglobin
