Question 1

Which of the following statements comparing respiration in fish and in mammals is correct?

Accepted Answer

In fish, the movement of the respiratory medium (water) is unidirectional, meaning that it moves in one direction through the gills. In mammals, however, the movement of the respiratory medium (air) is bidirectional, meaning that air moves in and out of the lungs during inhalation and exhalation. A is incorrect because while the respiratory medium (water in fish and air in mammals) does carry oxygen, it is not necessarily true that one carries more than the other. B is incorrect because the countercurrent exchange mechanism is actually seen in fish, where it allows for efficient oxygen uptake from the water. D is incorrect because both fish and mammals transport oxygen primarily by red blood cells in their respective circulatory systems.

Question 2

Which of the following mechanisms are used to regulate blood pressure in the closed circulatory system of vertebrates?
I changing the force of heart contraction
II constricting and relaxing smooth muscle in the walls of arterioles
III opening or closing precapillary sphincters

Accepted Answer

All three mechanisms (changing the force of heart contraction, constricting and relaxing smooth muscle in the walls of arterioles, and opening or closing precapillary sphincters) are used to regulate blood pressure in the closed circulatory system of vertebrates. By changing the force of heart contraction, the heart can pump more or less blood, which affects blood pressure. Constricting and relaxing smooth muscle in the walls of arterioles can also affect blood pressure by altering the resistance to blood flow. Opening or closing precapillary sphincters can regulate blood flow to specific areas, which can also affect blood pressure. Therefore, option D is the correct answer.

Question 3

You cut your finger, and after putting pressure on the wound for several minutes, you notice that it is still bleeding profusely. What may be the problem?

Accepted Answer

Platelets are necessary for the formation of blood clots, so if they are not functioning properly or there are too few of them, clotting will be impaired and the bleeding will continue. Mast cells and antigens are not directly involved in the clotting process, and high levels of hemoglobin would not affect clotting.

Question 4

The diagnosis of hypertension in adults is based on the ________.

Accepted Answer

The diagnosis of hypertension in adults is based on the blood pressure being greater than 140 mm Hg systolic and/or greater than 90 mm Hg diastolic.

Question 5

In order for blood to always flow unidirectionally through a closed circulatory system, the ________.

Accepted Answer

Valves are necessary to prevent backflow of blood and ensure unidirectional flow through the circulatory system.

Question 6

Although having evolved independently, the tracheal tubes of mammals and insects are both supported by rigid tissues. The trachea of a mammal is supported by cartilage, and the tracheae of an insect are supported by chitin. What selective pressure most likely led to the convergent evolution of these respiratory structures?

Accepted Answer

Both mammals and insects rely on air as the respiratory medium, which creates a risk of the tracheal tubes collapsing unless they are supported by rigid tissues. Therefore, the convergent evolution of respiratory structures in these two groups was likely driven by the need to prevent tracheal collapse. The other choices are not directly related to the need for structural support in the respiratory system.

Question 7

If the osmotic pressure on the venous side of capillary beds is lower than the hydrostatic pressure, then ________.

Accepted Answer

If the osmotic pressure on the venous side of capillary beds is lower than the hydrostatic pressure, it means that there is a net filtration pressure pushing fluids out of the capillaries and into the surrounding tissues. This can cause the accumulation of fluid in the tissues, leading to edema.

Question 8

Small swollen areas in the neck, groin, and axillary region are associated with ________.

Accepted Answer

Small swollen areas in the neck, groin, and axillary region are lymph nodes, and their enlargement is a sign of increased activity of the immune system. This can be due to infections, inflammation, or cancer.

Question 9

Humans infected with some types of parasitic worms develop a condition called elephantiasis, which is characterized by swelling of the limbs. Which of the following would be the most likely cause of elephantiasis?

Accepted Answer

Elephantiasis caused by parasitic worms is typically the result of lymphatic filariasis, in which the adult worms inhabit the lymphatic vessels and disrupt the normal flow of lymphatic fluid. The blockages can lead to swelling and can also make the affected limbs more vulnerable to bacterial and fungal infections. Option A is not correct because the immune system's response to the worms is not the primary cause of elephantiasis. Option B is not correct because cardiac output, which refers to the amount of blood the heart pumps per minute, is not directly related to lymphatic filariasis. Option D is also not correct because precapillary sphincters are involved in regulating blood flow to capillary beds, not lymphatic flow.

Question 10

When the air in a testing chamber is specially mixed so that its oxygen content is 10% and its overall air pressure is 400 mm Hg, then PO₂ is ________.

Accepted Answer

The answer of When the air in a testing chamber...

Question 11

Blood is pumped at high pressures in arteries from the heart to ensure that all parts of the body receive adequate blood flow. Capillary beds, however, would hemorrhage under direct arterial pressures. How does the design of the circulatory network contribute to reducing blood pressure to avoid this scenario?

Accepted Answer

The total cross-sectional diameter of the arterial circulation increases with progression from artery to arteriole to capillary, leading to a reduced blood pressure. This is because of the increase in total cross-sectional area causes a decrease in velocity of blood flow, which ultimately leads to a reduction in blood pressure.

Question 12

Countercurrent exchange in the fish gill helps to maximize ________.

Accepted Answer

Countercurrent exchange in the fish gill helps to maximize diffusion by allowing for a concentration gradient to be maintained along the length of the gill filaments, allowing for efficient gas exchange.

Question 13

To become bound to hemoglobin for transport in mammals, atmospheric molecules of oxygen must cross ________.

Accepted Answer

The answer of To become bound to hemoglobin for transport...

Question 14

Cyanide poisons mitochondria by blocking the final step in the electron transport chain. Human red blood cells placed in an isotonic solution containing cyanide are likely to ________.

Accepted Answer

The answer of Cyanide poisons mitochondria by blocking the final...

Question 15

Large proteins such as albumin remain in capillaries rather than diffusing out, resulting in the ________.

Accepted Answer

Large proteins such as albumin cannot easily cross the capillary walls and therefore create an osmotic pressure difference across the capillary walls. This results in a net movement of water back into the capillaries, helping to maintain blood volume and preventing excess fluid buildup in the tissues.

Question 16

A normal event in the process of blood clotting is the ________.

Accepted Answer

The activation of prothrombin to thrombin is a normal event in the process of blood clotting. Erythropoietin is a hormone involved in the production of red blood cells, fibrinogen is converted to fibrin during the clotting process, and hemoglobin is a protein found in red blood cells that carries oxygen.

Question 17

________ is a hormone that is released from the ________ to stimulate the production of red blood cells.

Accepted Answer

Erythropoietin is a hormone that is produced and released from the kidney in response to low oxygen levels. It stimulates the production of red blood cells in the bone marrow. Growth hormone is not involved in red blood cell production, and is produced by the pituitary gland, not the pancreas. Cortisol is produced by the adrenal gland and is involved in stress response, but not red blood cell production. Acetylcholine is a neurotransmitter, not a hormone, and is not involved in red blood cell production.

Question 18

Countercurrent exchange is evident in the flow of ________.

Accepted Answer

Countercurrent exchange occurs when the flow of one fluid moves in the opposite direction to the flow of another fluid, allowing for efficient transfer of substances between them. Water flowing across the gills of a fish and the blood within those gills is a classic example of countercurrent exchange, as it allows for efficient uptake of oxygen from the water into the bloodstream.

Question 19

Which of the following conditions would most likely be due to high blood pressure in a mammal?

Accepted Answer

High blood pressure can cause damage to the walls of blood vessels, leading to their rupture or bursting in capillary beds. This can result in bleeding and tissue damage.

Question 20

Blood cells that function to fight infection are called ________.

Accepted Answer

Leukocytes, also known as white blood cells, are responsible for fighting infections and foreign invaders in the body. Platelets are involved in blood clotting, erythrocytes are red blood cells responsible for carrying oxygen, and thrombi are clots that form in blood vessels.

Quiz 42: Circulation and Gas Exchange