Physiology: Quiz #5
A muscle that is actively contracting may have a cellular PO2 of 25 mm Hg. What happens to oxygen binding to hemoglobin at this low PO2? What is the PO2 of the venous blood leaving the active muscle?
As the PO2 falls, more oxygen is released. The PO2 of venous blood leaving the muscle is 25 mm Hg, same as the PO2 of the muscle
Why would a normal person breathing 100% O2 (at sea level) add very little additional O2 to the blood?
Because the normal person will have almost 100% saturation of Hb at the PO2 under normal conditions of the lungs.
What part of the body encounters the hemoglobin saturations included in this flat part of the curve?
Between lungs and resting tissues
How much O2 transported in the blood does resting tissue take in?
Blood returning in the veins from resting tissue is still 75% saturated (PO2 of 40 above) so resting tissues have taken in only 25% of the O2 from the blood.
Reticulocytosis is diagnosed when erythrocytes which have nuclei are seen in the blood. Where is the source (cause) of this problem- the liver, the blood vessels, or the bone marrow? Explain.
Bone marrow. Erythrocytes should not leave the bone marrow until they are fully mature (having expelled the nucleus), so these are leaving the marrow too quickly, immature.
Explain the role of carbonic anhydrase in allowing CO2 to be released from the body as a waste product.
CO2 is released from the body as a waste product at the lungs! It will be carried from the tissues (via systemic veins) in the form of H+ and HCO3-. Then, at the lungs, as the H+ increases in concentration, the carbonic anhydrase enzyme will catalyze the reaction H+ + HCO3- --> CO2 + H2O and this CO2 that is formed will be able to diffuse into the alveoli and be exhaled from there.
Draw a portion of the hemoglobin saturation curve. Draw only the part that shows hemoglobin traveling in systemic arteries and systemic veins of a resting individual.
Draw the part between PO2=100mm (systemic arteries) to PO2=40mm (systemic veins). This is Hb saturation between 100% saturation and 75% saturation.
As exercise continues in this individual (Say, as fatigue is set in), how would this curve be affected? You may draw in the "affected" curve above. Explain.
Due to the drop in pH (from lactic/anaerobic respiration) and rise in temperature, the hemoglobin affinity for O2 will be decreased and be less saturated at the PO2 levels for the standard curve... appears as a shift to the right.
Describe the structure of a hemoglobin molecule. What chemical element is essential for hemoglobin synthesis?
Four globular protein chains, each wrapped around a central heme group. Requires iron.
How does hemoglobin act as a buffer in systemic blood vessels? Would this be noticed in the systemic arteries or systemic veins?
HHb in the systemic veins
Why would increased temperatures have this effect (of decreasing its affinity for O2) on hemoglobin?
Hemoglobin is a protein and proteins have specific conformations that are sensitive to pH and increased temperatures. Think hydrogen bonds.
What happens to oxygen release when the exercising muscle warms up?
Hemoglobin releases more oxygen
If an individual has AB blood, what reaction (if any) would they have if transfused with type O blood? Explain.
No reaction, so this transfusion should be successful. The AB person has no antibodies to bind to the antigens on RBC and besides, type O red blood cells have no antigens. AB is the universal recipient; O is the universal donor.
Compare and contrast the proteins involved in forming a platelet plug, and the proteins involved in forming a clot. List one similarity and one difference.
Proteins involved in forming a platelet plug are collagen, and those secreted by the platelets when they are activated (including serotonin, thromboxane A, ADP) to cause platelet aggregation/blood vessel constriction, etc. Proteins involved in the coagulation cascade are many enzymes (initial activation is also collagen, a protein) when ultimately activate thrombin (enzyme) that will form fibrin from its precursor (fibronogen). Fibrin is a protein- the key protein- for forming a clot.
A person with AB blood type is transfused with type O red blood cells. What happens and why?
The AB recipient has no A or B antibodies and will not react to the red blood cells of any blood type
In the curve showing hemoglobin saturation, it appears "sigmoidal", that is, S-shaped. The flat part of the "S" occurs in higher PO2 levels. Why is this part of the curve flat?
The PO2 can drop from 100 (in the lungs) to PO2 of 40 (in resting tissues) and only lose 25% of it's hemoglobin to the tissues (by diffusion). This has a safety mechanism... a "reservoir" of oxygen to be used if PO2 drops even more dramatically.
In the curve showing hemoglobin saturation, the steep part of the curve occurs in intermediate PO2 levels. Why is this part of the curve steep?
The PO2 will drop between PO2 of 40 and PO2 of 20 (from 75% saturated, to 30% saturated). This is using the "reserved" oxygen because now your tissues need it -metabolism has increased and the use of O2 has increased.
Draw a portion of the hemoglobin saturation curve. Draw only the part that shows hemoglobin traveling in the systemic arteries and systemic veins of an exercising individual. Label these two regions on your graph.
The systemic arteries are the same as above (PO2=100mm). But the exercising individual will have systemic veins lower than the rest, so the PO2 must be <40mm, dropping the Hb saturation to below 75% saturation.
What part of the body encounters the hemoglobin saturations included in this steep part of the curve?
Tissues at exercise
One ABO blood type is called the "universal donor" and one is called the "universal recipient." Which types are these, and why are they given those names?
Type O: universal donor because these red blood cells lack A or B surface antigens and do not trigger an immune response. Type AB: universal recipient because these red blood cells have both A and B antigens, and no A or B antibodies.
the hormone that directs red blood cell synthesis is called __________. Where is it produced, and what is the stimulus for its production?
erythropoietin Produced primarily in the kidney in response to low oxygen
blood cell production is called _______. When and where does it occur?
hematopoiesis Embryo: yolk sac, liver, spleen, and bone marrow At birth: bone marrow Adulthood: axial skeleton and proximal ends of long bones
As the PO2 of plasma increases, what happens to the amount of oxygen that binds to hemoglobin?
increases
As the PO2 of plasma increases, what happens to the amount of oxygen that dissolves in plasma?
increases
a person who goes from sea level to a city that is 5000 feet above sea level begins to show an increased hematocrit within days. Draw the reflex pathway that links the hypoxia of high altitude to increased red blood cell production
low atmospheric oxygen ---> low arterial oxygen ---> sensed by kidney cells ---> secrete erythropoietin ---> acts on bone marrow ---> increased production of red blood cells.
In respiratory physiology, it is customary to talk of the PO2 of the plasma. Why is this not the most accurate way to describe the oxygen content of blood?
most oxygen is bound to hemoglobin, not dissolved in the plasma
What causes the exchange of oxygen and carbon dioxide between alveoli and blood or between blood and cells?
partial pressure gradients
Name four factors that influence the amount of oxygen that binds to hemoglobin. Which of these four factors is the most important?
PO2, temperature, pH, and the amount of hemoglobin available for binding. The amount of hemoglobin for binding is the most important
vonWillebrand factor is a protein secreted by platelets that enables exposed layers underlying the endothelium of blood vessels to bind to platelets. What process of wound repair in von Willebrand factor involved in?
Platelet plug
Acclimatization to high altitude involves changed that help to deliver oxygen more effectively to the tissues, despite reduced arterial PO2 levels. How do the kidneys play a role in this adjustment?
EPO is secreted from the kidneys in response to low PO2 levels in the atmosphere
If an individual has type A blood, what reaction (if any) would they have if transfused with type AB blood? Explain your response.
The person with type A blood has antibodies against the B antigen and this reaction will occur with the AB blood put into his system. Agglutination.
A person with O blood type is transfused with type A blood. What happens and why?
The type O recipient's anti-A antibodies will cause agglutination of the type A blood cells
the fluid portion of the blood, called _________ is composed mainly of _______
plasma, water
More than ____% of the oxygen in arterial blood is transported bound to hemoglobin. How is the remaining oxygen transported to the cells?
98% Remainder is dissolved in plasma
Anemia can be caused be any condition that decreases the oxygen-carrying capacity of the blood. Would a hematocrit reading of 25 qualify as anemia? Explain.
As long as the plasma levels are not unusually high, this is a low % of erythrocytes, which would decrease the oxygen-carrying capacity of the blood. Yes.
Factor XII is the first plasma protein to become active in the clotting pathway that we discussed in class (the one that takes place within the bloodstream, due to plasma proteins, called the Intrinsic Pathway). Factor XII can also be activated when blood is placed into a glass test tube. What component of this naturally occurring clotting pathway is being mimicked in the glass test tube when the blood makes contact with the tube? Explain.
Collagen- this triggers the cascade to begin by activating the first factor in the sequence.
Several factors affect the affinity of hemoglobin for O2. For example, high temperature will decrease the affinity of Hb for O2. So, at any given O2, Hb has less affinity for O2 than normal when the temperature is high. What will the new graph look like?
Curve will shift to the right, the same PO2 will have lower Hb saturation.
Does HbO2 binding increase, decrease, or not change with decreased pH?
decrease
EDTA is a calcium chelator (meaning, it binds to Ca++ prevents Ca++ from binding elsewhere). If the blood put into the test tube in #3 (above question) is added with EDTA, will be blood respond differently in the test tube? Explain.
Yes, blood clotting will occur with EDTA because Ca++ is required for almost every step in the cascade.
Would this adjustment be noticeable in a person's hematocrit reading? Why or why not?
Yes, we did this in the lab (#11). More red blood cells will be produced in response to EPO and therefore the % of red blood cells out of the whole blood will be more (higher hematocrit %)
If an individual has been injected with EPO (erythropoietin), would you expect their hematocrit to be affected? Would you expect the coagulation cascade to be affected? Explain.
Yes- hematocrit will be increased No- coagulation will not be affected by this cytokine/hormone.
