Question 1

During exercise, your heart rate can increase dramatically in order to meet the metabolic demands of your tissues. If your heart rate increased to 144 beats per minute, approximately how long would diastole last in a single cardiac cycle?

Accepted Answer

At a heart rate of 144 beats per minute, each cardiac cycle lasts about 0.42 seconds (60 seconds / 144 beats). Diastole typically takes up about two-thirds of the cardiac cycle, so it would last approximately 0.28 seconds, closest to 0.2 seconds.

Question 2

Which of the following molecules is least likely to be able to pass through a capillary wall?

Accepted Answer

Enzymes are large proteins that cannot easily pass through capillary walls or cell membranes. Sodium ions and glucose are small enough to pass through capillary walls, but they require transport proteins to move across cell membranes. Oxygen is small and non-polar, allowing it to easily diffuse across capillary walls and cell membranes.

Question 3

Bone marrow stem cells are sometimes used to treat certain blood cell diseases, such as

Accepted Answer

Bone marrow stem cells are often used to treat leukemia, a cancer of the blood cells. The stem cells are able to replace damaged or cancerous blood cells and help restore normal blood cell production. While bone marrow stem cells may also be used in the treatment of other blood disorders, such as anemia or hemophilia, they are most commonly used in the treatment of leukemia. Cardiovascular disease, which affects the heart and blood vessels, is not typically treated with bone marrow stem cells.

Question 4

Stem cells found in the red marrow inside bones

Accepted Answer

Stem cells found in the red marrow inside bones are known as hematopoietic stem cells, which are responsible for producing all blood cells and platelets. Therefore, they can differentiate into all blood cells and platelets, making choice D the correct answer.

Question 5

Hematocrit is the percentage of red blood cells in the blood. In adult humans, hematocrit is roughly 40-45%, but it can be much higher or lower in other animals. Consider the Weddell seal, a mammal that can dive and hold its breath underwater for upwards of 80 minutes. What is the hematocrit level of a Weddell seal, and why?

Accepted Answer

Weddell seals have a higher hematocrit level than adult humans because their bodies need to store more oxygen for their long dives underwater. A higher concentration of red blood cells allows for greater oxygen storage, enabling these seals to hold their breath for extended periods.

Question 6

During exercise, your cardiac output can increase dramatically in order to meet the metabolic demands of your tissues. If your heart rate increased to 150 beats per minute and the volume of blood pumped per beat is 75 mL, what is your cardiac output?

Accepted Answer

Cardiac output is calculated by multiplying the heart rate by the stroke volume (the volume of blood pumped per beat). 
Cardiac output = heart rate x stroke volume 
In this case, heart rate = 150 beats/min and stroke volume = 75mL/beat 
Cardiac output = 150 x 75 = 11,250 mL/min or 11.25 L/min

Question 7

Imagine that blood did not contain any dissolved proteins. What would likely happen when this abnormal blood flows through a capillary bed?

Accepted Answer

Dissolved proteins in the blood, such as albumin, contribute to the osmotic pressure that helps retain fluid within the capillaries. Without these proteins, the osmotic pressure would decrease, leading to an increased movement of fluid out of the capillaries into the surrounding tissue.

Question 8

You conduct a study with mice to determine whether giving them air with a higher-than-normal oxygen level results in their having a higher-than-normal oxygen content in their blood. What vessel should you draw blood from if you want to measure the highest potential level of oxygen content in the blood?

Accepted Answer

The pulmonary vein is the vessel that brings oxygenated blood from the lungs back to the heart. Drawing blood from this vessel will provide an accurate measure of the oxygen content in the blood, as it has just been oxygenated in the lungs. The other vessels listed either carry deoxygenated blood (inferior vena cava) or mix oxygenated and deoxygenated blood (superior vena cava, pulmonary artery) before reaching the heart, so they would not provide the highest potential level of oxygen content in the blood.

Question 9

An adult human's red blood cells are formed in the

Accepted Answer

Red blood cells, also known as erythrocytes, are formed in the bone marrow of adults. The spleen and liver play a role in breaking down old or damaged red blood cells. The thyroid gland has no involvement in the formation of red blood cells.

Question 10

How long do human red blood cells circulate in the blood before they wear out and have to be replaced?

Accepted Answer

Human red blood cells circulate in the blood for about 3 to 4 months before they wear out and are removed from circulation by the body. This is why the body constantly produces new red blood cells in the bone marrow to replace the old ones.

Question 11

Which of the following cells are phagocytes?

Accepted Answer

Monocytes and neutrophils are both types of white blood cells that are able to engulf and consume foreign particles, making them phagocytes. Basophils and eosinophils are involved in allergic responses and parasite defense, respectively, but are not primarily phagocytic. Lymphocytes are important for immune system function, but they are not phagocytes.

Question 12

Which of the following statements about blood clotting is true?

Accepted Answer

Threads of fibrin are formed from fibrinogen through a process of enzymatic conversion during clotting. These threads then aggregate and cross-link to form a fibrin clot. Option A is incorrect because the initial response to an injury is vasoconstriction rather than dilation, which helps to limit blood loss. Option B is also incorrect because platelets congregate specifically at the site of injury rather than in the interstitial fluid, where they release clotting factors and initiate the clotting response. Option C is also incorrect because it states the reverse process of what actually occurs during clotting.

Question 13

A man has been standing in one place without moving for a long time. You walk by and notice that his ankles are swollen. What is a likely explanation for this observation?

Accepted Answer

Since the man has been standing in one place without moving, the blood in the veins has not been properly circulated upward through the leg muscles. As a result, it pools at the lowest point, which is the ankles, causing them to swell. The other options are not likely explanations for this observation.

Question 14

What is the most common cause of anemia?

Accepted Answer

Iron deficiency is the most common cause of anemia. Iron is needed to produce hemoglobin, which carries oxygen in the blood. Without sufficient iron, the body cannot produce enough hemoglobin, leading to anemia. Vitamin deficiencies, inefficiencies in hemoglobin production, and low blood pressure can contribute to anemia, but they are not the most common causes.

Question 15

Plasma proteins are involved in all of the following activities except

Accepted Answer

Plasma proteins are not involved in carrying oxygen. This function is primarily carried out by red blood cells, specifically the protein hemoglobin within them.

Question 16

Which of the following can increase red blood cell concentration in a unit of blood?

Accepted Answer

Blood doping is the practice of artificially increasing the number of red blood cells in the bloodstream, typically by injecting erythropoietin (EPO) or receiving a blood transfusion. This leads to an increase in the concentration of red blood cells in a unit of blood. Training at low altitudes and hydration do not directly increase the number of red blood cells, and reducing blood levels of EPO would actually decrease the concentration of red blood cells.

Question 17

Blood clots are formed by platelets and the plasma protein

Accepted Answer

The answer of Blood clots are formed by platelets and...

Question 18

Sometimes when a person in a movie is stabbed or cut, blood forcefully sprays out of the wound. This is realistic only if the severed vessel is under a high degree of pressure. Which of the following vessels, if severed, would result in the most forceful spray of blood?

Accepted Answer

The aorta is the largest artery in the body and carries oxygenated blood away from the heart at a very high pressure. Therefore, if it is severed, it would result in the most forceful spray of blood.

Question 19

Which of the following statements about red blood cells is true?

Accepted Answer

Red blood cells are indeed shaped like biconcave disks, which helps to increase surface area for oxygen and carbon dioxide exchange.

Answer: C 
 Each red blood cell does contain approximately 1 million molecules of hemoglobin, which is the protein that binds to oxygen and helps transport it throughout the body.

Therefore, the correct choices are B and C.

Question 20

To view the path of blood flow through the heart and body, scientists and physicians perform an angiogram by injecting a dye into the blood and monitoring its movement. Imagine that this dye was injected into the pulmonary vein. Which of the following is the correct order of structures that the dye will flow through immediately after the pulmonary vein?

Accepted Answer

The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart. From the left atrium, blood flows into the left ventricle, then is pumped into the aorta, and from there it travels through the arteries to the rest of the body.

Quiz 23: Circulation