AP Biology : Circulatory Physiology

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Vascular Physiology

Which of the following traits is shared by both red blood cells (erythrocytes) and white blood cells (leukocytes)?

Possible Answers:

They all mature in bone marrow

They all contain mitochondria

They all contain a nucleus

They are all produced in bone marrow

Correct answer:

They are all produced in bone marrow

Explanation:

Erythrocytes and leukocytes are both produced and mature in bone marrow, with the exception of T cells, a type of white blood cell that matures in the thymus. Unlike leukocytes, red blood cells contain no nuclei or mitochondria, which could interfere with transporting oxygen, carbon dioxide, and nutrients.

Example Question #2 : Vascular Physiology

Jack has blood type B negative. He is in an accident and needs to receive a blood transfusion. From which of the following blood types can Jack receive blood?

Possible Answers:

B, Rh+

O, Rh+

AB, Rh-

O, Rh-

Correct answer:

O, Rh-

Explanation:

Because Jack has blood type B, he will form antibodies against blood types A and AB, as they contain a foreign antigen that his body will reject. Furthermore, he cannot accept any blood types that are Rh+, as this antigen will also seem foreign to his body. He can thus only accept from the blood types B- and O- (the universal donor type).

Example Question #3 : Understanding Hemoglobin And Transport

Which of the following statements about blood vessels is true?

Possible Answers:

Arteries have thicker walls than veins, which have thicker walls than capillaries

Pressure in veins is always higher than it is in arteries

Arteries contain valves to prevent backflow of blood

Capillaries contain oxygenated blood only

Correct answer:

Arteries have thicker walls than veins, which have thicker walls than capillaries

Explanation:

Arteries have thick, muscular walls that allow for constriction and flow direction, while veins have thin walls to carry blood.

Capillaries have extremely thin walls to allow exchange of oxygen, carbon dioxide, and nutrients with tissues, resulting in both oxygenated and deoxygenated blood in these vessels. Pressure in the arteries is always higher than in veins so that blood can be continuously pushed forward, negating the need for valves to prevent backflow. Such valves are present in veins and help to counteract gravity when returning blood to the heart.

Example Question #31 : Circulatory System

Which of the following will decrease hemoglobin's affinity for oxygen?

Possible Answers:

Measure affinity while hemoglobin is in the lungs

Decrease the partial pressure of oxygen

Decrease the acidity of the blood

Decrease the temperature

Correct answer:

Decrease the partial pressure of oxygen

Explanation:

Hemoglobin will have varying affinity for oxygen depending on its environment. For example, hemoglobin will have a very high affinity for oxygen in the lungs, where most oxygen is loaded onto the hemoglobin molecules. Once hemoglobin goes to the tissues of the body, there is a much lower oxygen tension. This decreased oxygen causes hemoglobin to have a lower affinity for oxygen and release the oxygen to the tissues.

Example Question #32 : Circulatory System

Which statement best describes hemoglobin?

Possible Answers:

It is comprised only of beta proteins and centers around iron

It is comprised of alpha and beta proteins and centers around iron

It is comprised of alpha and beta proteins and centers around copper

It is comprised only of alpha proteins and centers around iron

Correct answer:

It is comprised of alpha and beta proteins and centers around iron

Explanation:

Hemoglobin is comprised of two alpha and two beta proteins and uses iron to facilitate oxygen transportation. Some variations of hemoglobin, such as fetal hemoglobin, contain gamma proteins that changes the shape of the protein. Consistent with the theme that structure determines function, fetal hemoglobin has a higher affinity for oxygen than does adult hemoglobin. This is necessary since fetuses lack lungs; they obtain all of their oxygen from the hemoglobin of their mothers.

Example Question #1 : Circulatory Physiology

Where does transfer of oxygen to cells occur?

Possible Answers:

Veins

Lungs

Capillaries

Arteries

Correct answer:

Capillaries

Explanation:

Capillaries are the smallest blood vessels, which allow transport of oxygen and other small molecules. There are capillaries involved in gas exchange in the lungs, but it does not involve transfer of oxygen to the cells. Rather, it involves uptake of oxygen by red blood cells from the air inside the alveoli, and removal of carbon dioxide from the blood into the air in the alveoli to be exhaled. All other blood vessels have walls that are too thick to allow transport of any substances across them. The heart is the muscular pump of the circulatory system, which provides the pressure required to drive blood flow.

Example Question #121 : Systems Physiology

Which of the following transportation vessels carries deoxygenated blood away from the heart?

Possible Answers:

Pulmonary veins

Pulmonary arteries

Aorta

Vena cavae

Correct answer:

Pulmonary arteries

Explanation:

Arteries carry blood away from the heart, while veins transport blood towards the heart. Because the pulmonary arteries transport blood from the right ventricle towards the lungs to exchange carbon dioxide for oxygen, they contain deoxygenated blood.

The aorta, however, transports oxygenated blood from the left ventricle to the rest of the body for circulation. The pulmonary vein carries oxygenated blood from the lungs to the left ventricle and the vena cavae return deoxygenated blood to the right atrium.

Example Question #1 : Understanding Osmotic And Oncotic Pressure

Which of the following pressure changes would result in decreased fluid movement into the interstitium?

Possible Answers:

A decrease in interstitial hydrostatic pressure.

An increase in capillary hydrostatic pressure.

An increase in interstitial osmotic pressure.

An increase in capillary osmotic pressure.

Correct answer:

An increase in interstitial osmotic pressure.

Explanation:

As fluid moves through the capillary, the hydrostatic pressure decreases from the arteriole end to the venule end (fluid exits the capillary along the gradient). The osmotic pressure in the interstitium is relatively constant, and will be stronger than capillary hydrostatic pressure near the venule end. As a result, an increase in the interstitial osmotic pressure would cause less fluid to enter the interstitium, because there is less area in the bed where the capillary hydrostatic pressure is greater than the interstitial osmotic pressure.

Example Question #2 : Understanding Osmotic And Oncotic Pressure

As blood enters the arteriole end of a capillary some fluid generally exits into the interstium. When the blood flows through the venule end of the capillary some of this fluid is returned to the vessel. What best explains this transition?

Possible Answers:

Capillary hydrostatic pressure becomes stronger than the interstitial osmotic pressure

Interstitial osmotic pressure becomes stronger than capillary hydrostatic pressure

Interstitial hydrostatic pressure becomes stronger than the capillary osmotic pressure

Capillary osmotic pressure becomes stronger than interstitial hydrostatic pressure

Correct answer:

Interstitial osmotic pressure becomes stronger than capillary hydrostatic pressure

Explanation:

The capillary is the site of fluid exchange with the body's tissues. This fluid transfer is moderated by two factors: hydrostatic pressure and osmotic pressure. Hydrostatic pressure is the "pushing" force on water due to the presence of more fluid in one region than another. In general, larger fluid volumes generate higher hydrostatic pressure. Osmotic pressure is the "pulling" force on water due to the presence of solutes in solution. Albumin proteins are the main source of osmotic pressure in capillaries, pulling water into the blood.

At the arteriole end of the capillary, the hydrostatic pressure is stronger than the interstitial osmotic pressure and fluid is forced into the interstitium. Osmotic pressure remains relatively constant over the length of the capillary, but hydrostatic pressure drops sharply as it nears the venule end due to the initial loss of fluid volume. At that point, the interstitial osmotic pressure becomes stronger than the capillary's hydrostatic pressure. This forces fluid back into the capillary.

Example Question #3 : Understanding Osmotic And Oncotic Pressure

Why does fluid reenter the capillary from the interstitium at the venule end of the capillary bed?

Possible Answers:

Osmotic pressure is greater at the venule end of the capillary

Hydrostatic pressure is greater at the venule end of the capillary

Hydrostatic pressure is lower at the venule end of the capillary

Osmotic pressure is lower at the venule end of the capillary

Correct answer:

Hydrostatic pressure is lower at the venule end of the capillary

Explanation:

Hydrostatic pressure is the force of the fluid volume against a membrane, while osmotic pressure is related to the protein concentration on either side of a membrane pulling water toward the region of greater concentration.

When fluid enters the capillaries, it is initially pushed out because the hydrostatic pressure pressing outward is greater than the osmotic pressure pushing inward. Although osmotic pressure stays constant throughout the capillary length, hydrostatic pressure decreases towards the venule end of the capillary. This makes the osmotic pressure larger than the hydrostatic pressure, and pushes the fluid back into the capillary. 

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