EXAM 3
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530 Terms
What does a low pH do to the hemoglobin saturation of oxygen?
Decreases affinity
What is the normal pH of blood?
7.40 pH
How does hemoglobin help buffer acids in blood?
By binding to H+ Ions creating HHb
What is the symbol for hemoglobin?
Hb
When blood pH is low what happens to the amount of oxygen released?
Releases more O2
What is the law that affinity of hemoglobin for O2 is reduced by increases in PCO2 and H+?
Bohr effect
What is the Bohr effect?
The affinity of hemoglobin for O2 is reduced by increases in PCO2 and H+?
What causes blood pH to lower?
acid produced by active tissue
What does a high PCO2 do to hemoglobin saturation?
Decreases
What does CO2 do to the pH of blood?
Decreases the pH of blood
What does increasing the PCO2 do to the affinity of hemoglobin for O2?
decreases affinity
What does reducing BPG levels do?
increasing hemoglobin oxygen affinity
What does BPG stand for?
2,3- bisphosphoglycerate
What produces BPG and when?
Red blood cells as they metabolize glucose
When do BPG levels increase?
When O2 levels are low
What happens to BPG levels when O2 is low?
increase
What does BPG do in hemoglobin affinity?
It binds reversibly to hemoglobin and lowers its affinity for O2
What’s in the composition of Fetal hemoglobin that makes it differ from adult hemoglobin?
It contains 2 gamma polypeptide chains instead of the 2 beta chains of adult hemoglobin
What’s the functional difference of Fetal hemoglobin (HbF)?
Higher affinity for O2 than adult hemoglobin.
Why does fetal hemoglobin have a higher affinity for Oxygen than adult hemoglobin?
Because BPG can’t bind to the gamma polypeptide chains preventing it from lowering affinity
What is formed in part by the reversible reaction in the production of bicarbonate ions?
Carbonic acid-bicarbonate buffer system
What is pH controlled by in the production of bicarbonate ions?
the amount of H+ and the direction of the reaction
What happens when the pH is acidic?
The high levels of H+ combine with bicarbonate to produce co2 and water raising pH.
When pH is basic what happens?
The bicarbonate reaction goes to the right producing more H+
What is the effect of breathing on acid/base balance?
It can change the blood pH by changing the amount of CO2 in blood
What does slow shallow breathing do for the acid/base balance?
Allows CO2 to accumulate driving the equation to the right and making the blood more acidic
What does rapid deep breathing do for the acid/base balance?
reduces the amount of CO2 in the blood driving the equation to the left and making the blood more basic
What provides a fast system for balancing blood pH?
Respiratory ventilation
What’s needed for optimal gas exchange?
There must be a close match between ventilation and perfusion
What is the matching of ventilation and perfusion controlled by?
Auto-regulatory mechanisms
How does partial pressure of oxygen control optimal gas exchange?
By controlling perfusion by changing diameter arterioles
How does partial pressure of carbon dioxide control optimal gas exchange?
By controlling ventilation by changing diameter bronchioles
The partial pressure of oxygen controls perfusion is opposite of what?
The systematic circulation
When Po2 is low what happens to the arterioles?
They constrict shunting blood away form the alveoli with low ventilation and towards alveoli with higher ventilation
When Pco2 is high what happens to the bronchioles?
They cause dilation of bronchioles servicing alveoli with low ventilation allowing for faster elimination of CO2
What happens when Po2 is high in the arterioles?
They dilate increasing perfusion to alveoli with high ventilation
What happens when Pco2 is low to the bronchioles?
They constrict servicing the alveoli with high ventilation, shunting the air to alveoli with high CO2
What detects changes in CO2 , O2 , and pH in arterial blood?
Chemoreceptors
What are the two types of chemoreceptors?
Central chemoreceptors and peripheral chemoreceptors
What is the most powerful respiratory stimulant?
Increased CO2
What does an increase CO2 cause which excites the central chemoreceptors?
Acidosis
What is BPG a product of?
glycolysis
What is acidosis?
A condition characterized by an excess of acid in the blood and body tissues causing a pH of 7.35.
What do the chemoreceptor synapses do with the respiratory regulatory centers?
They increase the rate and depth of breathing
What are the two main peripheral chemoreceptors?
Aortic Arch, and carotid arteries
Under normal circumstances what effects does low O2 have on ventilation?
Limited
What do the peripheral chemoreceptors do?
Detect levels of O2
How far does Po2 need to drop for the peripheral chemoreceptors to produce an increase in ventilation?
Below 60 mm Hg
What excites peripheral chemoreceptors?
Decrease in pH
Increase in respiratory rate and depth
Po2 under 60 mm Hg
Where does CO2 go when it diffuse out of the RBCs?
It diffuses into the plasma and then into the alveoli
What is an adult hemoglobin composed of?
Red heme pigment and 4 polypeptide chains (2a and 2b)
How many molecules of oxygen can hemoglobin carry?
4
What in hemoglobin does oxygen bind to?
Binds to the Heme groups which contain iron
When a heme group combines with a molecule of oxygen what is formed?
oxyhemoglobin (Hb R)
What is the oxygen dissociation curve?
It is a graph comparing the percentage of hemoglobin saturation on the y-axis against partial pressure of oxygen in the blood on the x-axis.
What is the shape of an oxygen dissociation curve?
Sigmoid shaped (s-shape)
What does the oxygen dissociation curve show?
Oxygen saturation level in total blood hemoglobin at different partial pressures of O2
Why is the shape of an oxygen dissociation curve sigmoidal?
Because of the increased affinity of hemoglobin for Oxygen with each additional oxygen bound to the hemoglobin.
What is cooperative binding responsible for?
The Sigmoidal shape of the oxygen distribution curve
What happens to hemoglobin at low partial pressures when it is partially saturated?
Oxygen binding is fast, causing the rapid rise in the oxygen dissociation curve
Why does the oxygen dissociation curve plateau?
Because when hemoglobin is more saturated there are less open binding sites.
If you increase the partial pressure when hemoglobin is highly saturated what happens?
The curve plateaus, causing there not to be a large change in saturation
What is the partial pressure of oxygen in arterial blood?
95 mm Hg
What is the saturation of hemoglobin in arterial blood?
97% saturated
As blood flows through the systemic circulation what happens to the partial pressure of oxygen?
It drops to 40 mm Hg
What causes the release of oxygen from hemoglobin?
A drop in the partial pressure of oxygen.
As hemoglobin circulates through the blood what happens to it’s saturation of oxygen?
The saturation drops to 75%
What does the partial pressure of oxygen depend on in the tissues?
the activity of the tissue
In active tissue what is the partial pressure of oxygen?
≈20mm Hg
What is the saturation of oxygen in hemoglobin when tissue is active?
35-40% saturation
What causes a leftward shift in the oxygen dissociation curve?
An increased in hemoglobin affinity for oxygen
What causes a rightward shift in the oxygen dissociation curve?
A decreased in hemoglobin affinity for oxygen
What is caused by a decreased in hemoglobin affinity for oxygen
rightward shift in the oxygen dissociation curve
What is caused by an increased in hemoglobin affinity for oxygen?
Leftward shift in the oxygen dissociation curve
What factors effect the affinity of oxygen in hemoglobin?
➢ Temperature
➢ Blood pH
➢ PCO2
➢ BPG (2,3-bisphosphoglycerate)
a.k.a DPG (2,3-diphosphoglycerate)
What is BPG (2,3-bisphosphoglycerate)?
A molecule in red blood cells that binds to hemoglobin, lowering its affinity for oxygen and promoting oxygen release to tissues
What is DPG (2,3-diphosphoglycerate)?
A metabolic byproduct of glycolysis in red blood cells that regulates hemoglobin's affinity for oxygen.
What do high temperatures do to hemoglobin saturation?
Decrease hemoglobin saturation
What is the purpose of high temperatures decreasing hemoglobin oxygen affinity?
When active tissues produce heat it causes the dissociation curve ti lower allowing hemoglobin to release more oxygen at the active tissue.
What is the volume of the lungs affected by?
The forces that tend to collapse the lungs and forces that expand the lungs
What are the two forces that tend to collapse the lungs?
The stroma, and surface tension
What does the stroma do in the lungs?
Resist the expansion of the lungs
What does the stroma consist mostly of?
Elastic connective tissue
What creates surface tension in the lungs?
The alveolar fluid resisting the expansion of the alveoli
What produces surfactant?
Type II alveolar cells
What decreases the cohesiveness of water molecules in the lungs?
surfactant
What does surfactant do?
It prevents the alveoli from collapsing between breaths by decreases the cohesiveness of water molecules in the lungs
What in the pleural cavity holds the visceral pleura lining the lungs and the parietal pleura lining the thoracic cavity together?
Pleural fluid
What produces the force opposes the forces that tend to collapse the lungs
Pleural fluid
What type of pressure prevents the lungs from collapsing?
Positive transpulmonary pressures
What is the measure of how easily something stretches?
Compliance
What is compliance the measure of?
How easily something stretches
What is lung compliance the measure of? (specific)
The change in lung volume with a given change in transpulmonary pressure
What are the two factors that affect lung compliance?
Distensibility of lung tissue, and alveolar surface tension
For high compliance in healthy lungs what needs to happen with surface tension?
Surfactants need to keep alveolar surface tension low
For high compliance in healthy lungs what needs to happen with distensibility?
Distensibility must be high
What is distensibility?
The capacity of a hollow organ or vessel to stretch, expand, and increase in volume under pressure
What is Boyle’s law?
Air pressure is inversely related to the volume of the container
Who’s law states that “Air pressure is inversely related to the volume of the container”
Boyle’s law
What does Pulmonary Ventilation depend on?
Changes in pressure