Question 1

Countercurrent exchange in the fish gill helps to maximize ________.
A) blood pressure
B) diffusion
C) active transport
D) osmosis

Accepted Answer

Countercurrent exchange in the fish gill helps to maximize diffusion of oxygen and carbon dioxide between the water and the blood by maintaining a concentration gradient throughout the entire length of the respiratory surface. This allows for efficient gas exchange even in low oxygen environments.

Question 2

Countercurrent exchange is evident in the flow of ________.
A) water across the gills of a fish and the blood within those gills
B) blood in the dorsal vessel of an insect and that of air within its tracheae
C) air within the primary bronchi of a human and the blood within the pulmonary veins
D) water across the skin of a frog and the blood flow within the ventricle of its heart

Accepted Answer

Countercurrent exchange is a mechanism where substances flow in opposite directions in parallel tubes, maximizing the exchange of substances between them. This is seen in the flow of water across the gills of a fish and the blood within those gills, where oxygen diffuses from the water into the blood, while carbon dioxide diffuses from the blood into the water. The opposite flow of substances maximizes the exchange of oxygen and carbon dioxide between the water and the blood.

Question 3

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?
A) Blood flow through the capillaries is essentially frictionless, and this reduces the amount of pressure on their walls.
B) The total cross-sectional diameter of the arterial circulation increases with progression from artery to arteriole to capillary, leading to a reduced blood pressure.
C) Fluid loss from the arteries is high enough that pressure drops off significantly by the time blood reaches the capillaries.
D) Capillary beds have the thickest walls of any blood vessel to resist these high pressures.

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 reduces the pressure on capillary walls, preventing hemorrhaging.

Question 4

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
A) only I and II
B) only I and III
C) only II and III
D) I, II, and III

Accepted Answer

All three mechanisms are used to regulate blood pressure in vertebrates' closed circulatory system. Changing the force of heart contraction adjusts the volume of blood pumped out of the heart, while constricting or relaxing smooth muscles in the arterioles can alter the diameter of blood vessels and subsequently the blood flow to organs. Opening or closing precapillary sphincters acts as a gatekeeper for the exchange of nutrients and gases between blood and tissues. Thus, all these mechanisms work in collaboration to maintain proper blood pressure levels.

Question 5

The diagnosis of hypertension in adults is based on the ________.
A) measurement of fatty deposits on the endothelium of arteries
B) measurement of the LDL/HDL ratio in peripheral blood
C) percentage of blood volume made up of platelets
D) blood pressure being greater than 140 mm Hg systolic and/or greater than 90 mm Hg diastolic

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 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?
A) Both mammals and insects have similar oxygen needs.
B) When air is the respiratory medium, there is a greater risk that the tracheal tubes will collapse.
C) Insects and mammals both keep their internal temperature constant.
D) A decrease in environmental carbon dioxide made structural support necessary.

Accepted Answer

The risk of collapse is a common problem for respiratory structures that rely on air as the medium for gas exchange. Both mammalian and insect tracheal tubes faced this challenge, which likely selected for the evolution of rigid support structures to prevent collapse.

Question 7

Small swollen areas in the neck, groin, and axillary region are associated with ________.
A) increased activity of the immune system
B) blood sugar that is abnormally high
C) dehydration
D) sodium depletion

Accepted Answer

Small swollen areas in the neck, groin, and axillary region are associated with increased activity of the immune system, specifically the lymphatic system. These swollen areas, also known as lymph nodes, can become enlarged as they work to trap and destroy foreign substances such as bacteria or viruses.

Question 8

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 ________.
A) 400 mm Hg
B) 82 mm Hg
C) 40 mm Hg
D) 4 mm Hg

Accepted Answer

The partial pressure of oxygen (PO₂) is calculated by multiplying the percentage of oxygen by the total pressure: 10% of 400 mm Hg is 40 mm Hg.

Question 9

Which of the following statements comparing respiration in fish and in mammals is correct?
A) The respiratory medium for fish carries more oxygen than the respiratory medium of mammals.
B) A countercurrent exchange mechanism between the respiratory medium and blood flow is seen in mammals but not in fish.
C) The movement of the respiratory medium in mammals is bidirectional, but in fish it is unidirectional.
D) In blood, oxygen is primarily transported by plasma in fish, but by red blood cells in mammals.

Accepted Answer

In fish, respiration occurs through gills, where water flows in a unidirectional manner over the gill filaments. In mammals, respiration occurs in the lungs, where the movement of air is bidirectional. Therefore, option C is the correct comparison between respiration in fish and mammals. Option A is incorrect because fish extract oxygen from water, which carries less oxygen compared to air. Option B is incorrect because countercurrent exchange mechanism is seen in both fish and mammals. Option D is incorrect because oxygen is mainly transported by red blood cells in both fish and mammals.

Question 10

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?
A) Platelets are not functioning properly, or there are too few to be effective.
B) Mast cells are not releasing their chemical messengers.
C) There are too many antigens to allow clotting.
D) Hemoglobin levels are too high to allow clotting.

Accepted Answer

Platelets are responsible for forming clots to stop bleeding, and if they are not functioning properly or there are too few, clotting may not occur and bleeding will persist. Mast cells releasing their chemical messengers, too many antigens, and high hemoglobin levels do not directly impact the clotting process.

Question 11

A normal event in the process of blood clotting is the ________.
A) production of erythropoietin
B) conversion of fibrin to fibrinogen
C) activation of prothrombin to thrombin
D) synthesis of hemoglobin

Accepted Answer

The activation of prothrombin to thrombin is a normal step in the process of blood clotting. Option A is incorrect as erythropoietin is a hormone that stimulates the production of red blood cells. Option B is incorrect as fibrinogen is converted to fibrin during blood clotting, not the other way around. Option D is incorrect as hemoglobin is synthesized in red blood cells and is mainly responsible for carrying oxygen.

Question 12

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?
A) The infected human's immune system is fighting the worms.
B) The worm infection is causing a decrease in cardiac output.
C) The worms are blocking the lymph vessels.
D) More blood is flowing through precapillary sphincters.

Accepted Answer

Elephantiasis is caused by the blocking of the lymph vessels by parasitic worms, which results in the accumulation of lymph and fluid in the tissues and the characteristic swelling. The other choices are not associated with elephantiasis.

Question 13

Which of the following conditions would most likely be due to high blood pressure in a mammal?
A) bursting of blood vessels in capillary beds
B) inability of the right ventricle to contract
C) reversal of normal blood flow direction in arteries
D) destruction of red blood cells

Accepted Answer

High blood pressure can cause damage to the fragile capillary walls, leading to their bursting and ultimately resulting in internal bleeding. This can cause various health complications such as vision problems, kidney damage, brain damage or even death. The other options, B, C, and D, are not directly related to high blood pressure.

Question 14

Blood cells that function to fight infection are called ________.
A) platelets
B) leukocytes
C) erythrocytes
D) thrombi

Accepted Answer

Leukocytes, also known as white blood cells, are responsible for fighting infections and foreign invaders in the body. Platelets function in blood clotting, erythrocytes carry oxygen, and thrombi are blood clots.

Question 15

________ is a hormone that is released from the ________ to stimulate the production of red blood cells.
A) Growth hormone; pancreas
B) Erythropoietin; kidney
C) Cortisol; adrenal gland
D) Acetylcholine; bone marrow

Accepted Answer

Erythropoietin is a hormone that is released from the kidney to stimulate the production of red blood cells. Growth hormone is released from the pituitary gland, cortisol is released from the adrenal gland, and acetylcholine is a neurotransmitter involved in muscle contraction and nerve transmission, not hormone regulation.

Question 16

If the osmotic pressure on the venous side of capillary beds is lower than the hydrostatic pressure, then ________.
A) hemoglobin will not release oxygen
B) fluid will tend to accumulate in tissues
C) the pH of the interstitial fluids will increase
D) plasma proteins will escape through the endothelium of the capillaries

Accepted Answer

If the osmotic pressure on the venous side of capillary beds is lower than the hydrostatic pressure, fluid will tend to accumulate in tissues. This is because hydrostatic pressure forces fluid out of the capillaries, while osmotic pressure pulls fluid back in, and if the osmotic pressure is lower, then the pull of fluid back into the capillaries is weaker than the force pushing it out. This can lead to edema and swelling of tissues. The other answer choices are not related to the pressure differentials in capillary beds.

Question 17

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 ________.
A) retain the normal cell shape, but the mitochondria will be poisoned
B) lyse as the cyanide concentration increases inside the cell
C) switch to anaerobic metabolism
D) be unaffected

Accepted Answer

Red blood cells lack mitochondria, so cyanide, which affects mitochondrial function, will not impact them.

Question 18

In order for blood to always flow unidirectionally through a closed circulatory system, the ________.
A) blood vessels farthest from the heart must have valves
B) capillaries must have a thick endothelium
C) arteries must be elastic
D) pressure in all vessels must be equal

Accepted Answer

Valves are essential for ensuring that blood flows in only one direction in blood vessels farthest from the heart, such as veins, where the blood flow is slower and less pressurized. This prevents backflow and ensures that blood continues to travel towards the heart.

Question 19

Large proteins such as albumin remain in capillaries rather than diffusing out, resulting in the ________.
A) loss of osmotic pressure in the capillaries
B) development of an osmotic pressure difference across capillary walls
C) loss of fluid from capillaries
D) increased diffusion of hemoglobin

Accepted Answer

Large proteins such as albumin are not able to easily pass through capillary walls and therefore remain within the blood vessels. This results in the development of an osmotic pressure difference across the walls of the capillaries, as the presence of these large molecules within the blood creates a higher solute concentration within the vessel. This difference in osmotic pressure helps to drive the movement of fluids and small molecules (such as nutrients and waste products) across the capillary walls, allowing for the exchange of materials between the blood and the surrounding tissues.

Question 20

To become bound to hemoglobin for transport in mammals, atmospheric molecules of oxygen must cross ________.
A) one membrane-that of the lining in the lungs-and then bind directly to hemoglobin, a protein dissolved in the plasma of the blood
B) two membranes-in and out of the cell lining the lung-and then bind directly to hemoglobin, a protein dissolved in the plasma of the blood
C) four membranes-in and out of the cell lining the lung, in and out of the endothelial cell lining an alveolar capillary-and then bind directly to hemoglobin, a protein dissolved in the plasma of the blood
D) five membranes-in and out of the cell lining the lung, in and out of the endothelial cell lining an alveolar capillary, and into the red blood cell-to bind with hemoglobin

Accepted Answer

Oxygen must cross five membranes: in and out of the alveolar epithelial cell, in and out of the endothelial cell of the capillary, and into the red blood cell where it binds to hemoglobin.

Quiz 42: Circulation and Gas Exchange

Countercurrent exchange in the fish gill helps to maximize ________.

Countercurrent exchange is evident in the flow of ________.

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

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

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

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 ________.

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

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?

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

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?

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

Blood cells that function to fight infection are called ________.

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

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

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 ________.

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

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

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