EXAM 4

What short-term changes in an animal's cardiovascular function might facilitate using skeletal muscles to escape from a dangerous situation?

An increase in blood pressure and cardiac output combined with the diversion of more blood to the skeletal muscles would increase the capacity for action by increasing the rate of blood circulation and delivering more O2O2 and nutrients to the skeletal muscles.

Explain why a physician might order a white cell count for a patient with symptoms of an infection.

An increase in the number of white blood cells (leukocytes) may indicate that the person is combating an infection.

Which molecules trigger the adaptive immune response?

Antigen (A foreign molecule that elicits a specific response by a lymphocyte is called an antigen.)

Metabolism of carbohydrates and fats requires several nitrogen-containing molecules, such as NAD+/NADH, but is not a significant source of nitrogen-containing waste. Why?

As cofactors for the enzymes that catalyze metabolism, nitrogen-containing molecules such as NAD+/NADH are "recycled" during cellular respiration. They thus are not broken down and their components are not absorbed or excreted.

Which of the following cell types carries out humoral immunity?

B cells (Humoral immunity involves B cell activation and the production of antibodies by plasma cells.)

Which statement best describes the difference in responses of effector B cells (plasma cells) and cytotoxic T cells?

B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells.

Why does altitude have almost no effect on an animal's ability to rid itself of CO2CO2 through gas exchange?

Because CO2 is such a small fraction of atmospheric gas (0.29 mm Hg/760 mm Hg, or less than 0.04%), the partial pressure gradient of CO2 between the respiratory surface and the environment always strongly favors the release of CO2 to the atmosphere.

Pus is both a sign of infection and an indicator of immune defenses in action. Explain.

Because pus contains white blood cells, fluid, and cell debris, it indicates an active and at least partially successful inflammatory response against invading pathogens.

Why does our immune system not usually attack our own healthy tissues?

Because such lymphocytes are destroyed or rendered nonfunctional (Some B and T cells that have receptors for the body's own molecules are destroyed by apoptosis; others are rendered nonfunctional.)

How does air in the lungs differ from the fresh air that enters the body during inspiration?

Because the lungs do not empty completely with each breath, incoming and outgoing air mix. Lungs thus contain a mixture of fresh and stale air.

Why do freshwater fish excrete a large amount of very dilute urine?

Because they live in a hypoosmotic solution, their cells take up excess water that must be excreted. (Freshwater fish take in a lot of water from the environment through osmosis and must excrete large amounts of water in dilute urine from their kidneys.)

What is the function of antidiuretic hormone (ADH) in the body?

During times of higher solute concentrations, ADH causes more water to be released from the nephrons to be reabsorbed by the blood. (ADH signals the nephrons to release more water from the filtrate into the interstitial fluid. The water is then reabsorbed into the blood.)

After a heavy rain, earthworms come to the surface. How would you explain this behavior in terms of an earthworm's requirements for gas exchange?

Earthworms need to keep their skin moist for gas exchange, but they need air outside this moist layer. If they stay in their water logged tunnels after a heavy rain, they will suffocate because they cannot get as much O2 from water as from air.

What would you expect to see in an individual with low levels of blood protein in the capillaries?

Edema in the body tissues

How do stem cells from the bone marrow of an adult differ from embryonic stem cells?

Embryonic stem cells are pluripotent rather than multipotent, meaning they can give rise to many rather than a few different cell types.

Which is an accurate pairing of a key excretory function with its definition?

Excretion moves urine, the processed filtrate, out of the kidney, through the ureter and the bladder, and finally out of the body via the urethra.

How does the flow of a fluid in a closed circulatory system differ from the movement of molecules between cells and their environment with regard to distance traveled, direction traveled, and driving force?

In a closed circulatory system, an ATP-driven muscular pump generally moves fluids in one direction on a scale of millimeters to meters. Exchange between cells and their environment relies on diffusion, which involves random movements of molecules. Concentration gradients of molecules across exchange surfaces can drive rapid net diffusion on a scale of 1 mm or less.

Which of the following types of cells initiate a secondary immune response?

Memory cells (The secondary immune response, which depends on memory cells, provides long-term protection after exposure to a pathogen.)

Parasitic wasps inject their eggs into host larvae of other insects. If the host immune system doesn't kill the wasp egg, the egg hatches and the wasp larva devours the host larva as food. Suggest an explanation for why some insect species initiate an innate immune response to a wasp egg, but others cannot.

Mounting an immune response would require recognition of some molecular feature of the wasp egg not found in the host. It might be that only some potential hosts have a receptor with the necessary specificity.

In the condition known as myasthenia gravis, antibodies bind to and block certain receptors on muscle cells, preventing muscle contraction. What type of disorder is myasthenia gravis?

Myasthenia gravis is considered an autoimmune disease because the immune system produces antibodies against self molecules (certain receptors on muscle cells).

Why is an internal location for gas exchange tissues advantageous for terrestrial animals?

Their interior position helps gas exchange tissues stay moist. If the respiratory surfaces of lungs extended into the terrestrial environment, they would quickly dry out, and diffusion of O2 and CO2 across these surfaces would stop.

How do aquatic birds such as the wandering albatross avoid becoming dehydrated even though they live in an environment that is almost entirely salt water?

They actively transport excess salt from the blood into secretory tubules found in special excretory glands. (This process is called countercurrent exchange. The excess salt is then excreted through the bird's nasal glands.)

Which statement describes what would most likely happen to microbes in the blood?

They are phagocytosed by macrophages in the spleen.

Which of the following is a general property of epithelial cells?

They display an apical and a basal surface that define cell polarity.

What do macrophages and neutrophils have in common?

They phagocytize pathogens.

Which of these is not part of insect immunity?

activation of natural killer cells

An open circulatory system __________.

allows interstitial fluid to mix freely with vascular fluid

Local swelling, increased blood flow, and fever are all parts of __________.

an inflammatory response

Metanephridia are found in __________ and function in __________.

annelids; excretion and osmoregulation (Metanephridia are found in most annelids, including earthworms, and function in osmoregulation and excretion. The metanephridium has internal openings that collect body fluids.)

New flu shots are needed every year to protect against infection because of __________.

antigenic variation (Frequent mutation in flu viruses means that the surface antigens on viruses from this year are not the same as those to which an immune response was mounted last year.)

Your blood pressure is 120/70. The "120" indicates __________, and the "70" indicates __________.

arterial pressure during heart contraction; arterial pressure during heart relaxation

For a body surface to be a respiratory surface, it must __________.

be thin and moist

All of the following processes occur in the nephron of the kidney except __________.

blood cell formation (Blood cells are not formed in the kidneys. Instead, the nephron filters blood, secretes hydrogen ions and other substances to maintain a constant pH for body fluids, and reabsorbs sugars, vitamins, and other nutrients.)

When you exhale, __________.

both the diaphragm and the rib muscles relax (Exhalation occurs when the rib muscles and diaphragm relax, restoring the thoracic cavity to its smaller volume.)

The function of the pulmonary circuit in a dog is to __________.

carry carbon dioxide to the lungs and pick up oxygen from the lungs

Once you have been exposed to an antigen, you develop immunity against the same antigen because __________.

certain lymphocytes enable the rapid formation of the proper antibodies (These lymphocytes are called memory cells. On later exposure to the antigen, a rapid response occurs and effector cells are quickly produced.)

The proliferation of the B lymphocyte to which a specific antigen binds is referred to as __________.

clonal selection (When an antigen binds to a B cell or a T cell, that cell proliferates, forming clones of effector cells with the same specificity.)

A mutation that results in a nonfunctioning nitric oxide receptor would cause __________.

decreased vasodilation

In the alveoli and lung capillaries, carbon dioxide and oxygen are exchanged by means of __________.

diffusion (Oxygen and carbon dioxide exchange occurs across the epithelium of the alveoli by diffusion.)

The high osmolarity of the renal medulla is maintained by all of the following except

diffusion of salt from the descending limb of the loop of Henle.

What is the correct order of structures through which air passes as it is inhaled by a typical mammal?

Nasal cavity, pharynx, larynx, trachea, bronchus, bronchiole, alveolus (Air enters through the nostrils and nasal cavity and passes through the pharynx and the larynx. From there, the air passes into the trachea and into the two bronchi. Each bronchus branches repeatedly into bronchioles, which eventually terminate in tiny air sacs called alveoli.)

Which type of cell is responsible for causing apoptosis in cancer cells and virus-infected cells?

Natural killer cells (Once natural killer cells are attached to a virus-infected cell or cancer cell, they release chemicals that lead to the programmed death of the cell.)

Is being infected with HIV the same as having AIDS? Explain.

No. AIDS refers to a loss of immune function that can occur over time in an individual infected with HIV. However, certain multi-drug combinations ("cocktails") or rare genetic variations usually prevent progression to AIDS in people infected with HIV.

Is immunological memory after a natural infection fundamentally different from immunological memory after vaccination? Explain.

No. Immunological memory after a natural infection and that after vaccination are very similar. There may be minor differences in the particular antigens that can be recognized in a subsequent infection.

Which of the following is a function of erythrocytes (red blood cells)?

None of the listed responses is correct. (The main function of erythrocytes is the transport of oxygen. The other choices listed are all functions of leukocytes.)

In the absence of infection, what percentage of cells in human blood are leukocytes?

One microliter of blood contains about 5 million erythrocytes and 5,000 leukocytes, so leukocytes make up only about 0.1% of the cells in the absence of infection.

Which of the following functions of plasma-cell-secreted antibodies promotes phagocytosis of foreign bacteria?

Opsonization (In opsonization, antibodies bind to bacterial antigens and essentially "tag" the cell for phagocytosis by neutrophils and macrophages.)

Which type of epithelial tissue would you suppose covers the gills of axolotls?

Simple squamous epithelium

Treatment of antibodies with a particular protease clips the heavy chains in half, releasing the two arms of the Y-shaped molecule. How might the antibodies continue to function?

Since the antigen-binding site is intact, the antibody fragments could neutralize viruses and opsonize bacteria.

African lungfish, which are often found in small stagnant pools of fresh water, produce urea as a nitrogenous waste. What is the advantage of this adaptation?

Small stagnant pools do not provide enough water to dilute the toxic ammonia.

Nitroglycerin (the key ingredient in dynamite) is sometimes prescribed for heart disease patients. Within the body, nitroglycerin is converted to nitric oxide (see Concept 42.3). Why would you expect nitroglycerin to relieve chest pain caused by narrowing of the cardiac arteries?

The chest pain results from inadequate blood flow in coronary arteries. Vasodilation promoted by nitric oxide from nitroglycerin increases blood flow, providing the heart muscle with additional oxygen and thus relieving the pain.

Why is it important that the AV node delay the electrical impulse moving from the SA node and atria to the ventricles?

The delay allows the atria to empty completely, filling ventricles fully before they contract.

A doctor might give bicarbonate (HCO3−) to a patient who is breathing very rapidly. What is the doctor assuming about the patient's blood chemistry?

The doctor is assuming that the rapid breathing is the body's response to low blood pH. Metabolic acidosis, the lowering of blood pH as a result of metabolism, can have many causes, including complications of certain types of diabetes, shock (extremely low blood pressure), and poisoning.

Suppose that after you exercise regularly for several months, your resting heart rate decreases, but your cardiac output at rest is unchanged. Based on these observations, what other change in the function of your heart at rest likely occurred?

The heart, like any other muscle, becomes stronger through regular exercise. You would expect a stronger heart to have a greater stroke volume, which would allow for the decrease in heart rate.

What is the primary cause of the low velocity of blood flow in capillaries?

The large total cross-sectional area of the capillaries

Which is an accurate statement about the anatomy of the human excretory system?

The loop of Henle is located between the proximal tubule and the distal tubule.

In a series of immune system experiments, the thymus glands were removed from baby mice. Which of the following would you predict as a likely result?

The mice readily accepted tissue transplants. (The thymus is necessary for the proper maturation of T cells. Without helper and cytotoxic T cells, there would no effective immune response.)

As filtrate passes through the long loop of Henle, salt is removed and concentrated in the interstitial fluid of the kidney medulla. Because of this high salt concentration, the nephron is able to __________.

establish a hyperosmotic interstitial medullary concentration (Because the interstitial fluid is hyperosmotic, water can be drawn from the filtrate in the collecting duct.)

In a marine environment, animals that are isosmotic relative to their environment __________.

experience no net water loss by osmosis (One solution for a marine animal is to be isosmotic with its saltwater environment. Such osmoconformers do not actively adjust internal osmolarity.)

Nitrogen is absent from

fatty acids.

The primary sealant(s) that plug(s) leaks in damaged blood vessels is/are __________.

fibrin

In each nephron of the kidney, the glomerulus and Bowman's capsule __________.

filter the blood and capture the filtrate (Using hydrostatic pressure, plasma is forced through the walls of the glomerulus, becoming filtrate as it crosses and then collecting within Bowman's capsule.)

Which process in the nephron is least selective?

filtration

Many insects, birds, and other reptiles excrete nitrogenous wastes in the form of uric acid, which __________.

forms solids that are relatively insoluble and nontoxic (Uric acid precipitates out of solution and can be stored within an egg as a solid that is left behind when the animal hatches.)

In osmosis, water undergoes net diffusion to an area of lower

free water concentration.

The bed of capillaries in a vertebrate kidney where water, urea, and salts are filtered out of the blood is the __________.

glomerulus (The nephron consists of a single long tubule and a ball of capillaries called the glomerulus.)

The body produces antibodies complementary to foreign antigens. The process by which the body comes up with the correct antibodies to a specific invader is most like __________.

going to a shoe store and trying on shoes until you find a pair that fits. (Unless an immune cell with the appropriate surface receptor exists prior to the infection, no immune response will be possible. Antigens will be presented to a number of lymphocytes, each containing any one of millions of antigen receptors, until a match is found.)

Osmoconformers are animals that __________.

have an internal environment isosmotic with their external environment

Pulse is a direct measure of

heart rate.

Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arterioles has a

higher PO2

A vaccine may contain __________.

inactivated disease-causing microbes (Inactivation may result from killing the organisms or by treatments that weaken or remove the disease-causing aspects while leaving antigens intact.)

Alcohol consumption increases urinary output because alcohol __________.

inhibits ADH production and release (Alcohol can disturb water balance by inhibiting the release of ADH.)

Chemicals produced by virus-infected cells that alert neighboring cells to prepare a defense are called __________.

interferons

The loops of Henle in the kidneys of a desert kangaroo rat are much longer than those in a white laboratory rat because the __________.

kangaroo rat is adapted to living in an environment where water is scarce (The longer loops of Henle allow more water to be absorbed back into the body.)

Heart valves function to __________.

keep blood moving forward through the heart

Blood returning to the mammalian heart in a pulmonary vein drains first into the

left atrium.

Vaccination increases the number of

lymphocytes with receptors that can bind to the pathogen.

Countercurrent flow in the gills of a fish __________.

maintains a gradient that enhances diffusion.

Dehydration in animals __________.

may be less damaging in the presence of sugar (In nematodes, a sugar, trehalose, replaces the lost water, preventing proteins and cell membranes from being damaged by dehydration.)

A type of cell that makes immunizations effective is the __________.

memory B cell (The secondary immune response, which is due to memory cells, provides long-term protection after exposure to a pathogen.)

The filtrate formed by the nephrons in the kidney is not urine. The filtrate is first refined and concentrated by the processes of __________, which form the urine that leaves the body.

reabsorption and secretion (Reabsorption returns valuable molecules filtered from the plasma and secretion permits selected substances, such as salts and hydrogen ions, to be removed more rapidly from the blood than by filtration alone.)

Unlike an earthworm's metanephridia, a mammalian nephron

receives filtrate from blood instead of coelomic fluid.

If microorganisms penetrate the innate defenses, an inflammatory response may be initiated by the __________.

release of chemicals such as histamine by mast cells

The tertiary structure of a protein

relies on multiple weak bonds between side chains.

Blood leaves the inferior vena cava and flows directly into the __________.

right atrium

When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?

rising CO2

Question 3:A bacterium or other particle taken up by phagocytosis is

routed to lysosomes for degradation.

A viral infection in a cell results in __________.

secretion of interferon (Interferon is released by virus-infected cells. Taken up by uninfected cells, it induces them to produce molecules that inhibit viral replication.)

The lowest osmotic potential inside a nephron will be found in __________.

the thick segment of the ascending limb of the loop of Henle and the distal tubule (The thick segment of the ascending limb of the loop of Henle actively pumps NaCl out of the tubule, making the filtrate increasingly dilute. By the time the filtrate reaches the distal tubule, it is hypoosmotic to body fluids.)

Which of the following respiratory systems is not closely associated with a blood supply?

the tracheal system of an insect.

Pressure is greatest in the ventricles when __________.

the ventricles contract

When we compare the structures and functions of arteries and veins, we find that the walls of arteries are __________, the blood pressure inside arteries is __________, and the blood in arteries is moving __________ the heart.

thicker; higher; away from

The primary nitrogen-containing compound excreted by our kidneys is __________.

urea (Mammals, most adult amphibians, and aquatic turtles excrete urea.)

The most effective molecule for nitrogenous waste disposal in desert animals would be __________.

uric acid because it requires very little water for excretion (Uric acid can be excreted as a paste of crystals suspended in a little water. This is an important adaptation for conserving water in a desert.)

An epitope associates with which part of an antigen receptor or antibody?

variable regions of a heavy chain and light chain combined

All known birds and mammals have __________.

a double circulatory system and a four-chambered heart

How does an increase in the CO2 concentration in the blood affect the pH of cerebrospinal fluid?

An increase in blood CO2 concentration causes an increase in the rate of CO2 diffusion into the cerebrospinal fluid, where the CO2 combines with water to form carbonic acid. Dissociation of carbonic acid releases hydrogen ions, decreasing the pH of the cerebrospinal fluid.

Which respiratory organ is most often found only in fully aquatic animals?

Gills

Besides helper T cells, what are two other types of cells that HIV infects?

Macrophages and brain cells

Which of the following animals generally has the lowest volume of urine production?

a marine bony fish

Natural selection should favor the highest proportion of juxtamedullary nephrons in which of the following species?

a mouse species living in a desert

In a fish, blood circulates through __________, whereas in a mammal, it circulates through __________.

one circuit; two circuits (Fish have a single circuit that utilizes one atrium and one ventricle, whereas the mammalian heart has a double circuit.)

Question 3:As a property of enzymes, cooperatively refers to

one enzyme subunit altering the behavior of others.

One feature that amphibians and humans have in common is

the number of circuits for circulation.

The idea behind vaccination is to induce __________ without requiring the vaccinated individual to get sick.

the primary immune response

If a molecule of CO2 released into the blood in your left toe is exhaled from your nose, it must pass through all of the following except

the pulmonary vein.

If a child were born without a thymus gland, what cells and functions of the immune system would be deficient? Explain.

A child lacking a thymus would have no functional T cells. Without helper T cells to help activate B cells, the child would be unable to produce antibodies against extracellular bacteria. Furthermore, without cytotoxic T cells or helper T cells, the child's immune system would be unable to kill virus-infected cells.

In insects, which of the following is analogous to mammalian epithelial tissue, in that it serves as a first line of defense against infection?

A chitinous exoskeleton

The SA node generates an electrical impulse from its location in __________.

the right atrium, causing atrial contraction

What do the antibodies secreted by plasma cells (the effector cells of humoral immunity) do to attack their targets?

- Cross-link soluble antigen molecules, forming immobile aggregates - Clump cells together so that phagocytes can ingest them - Activate complement to form a pore in the membrane of the targets - Attach to antigens and block their activity

Which of the following is a function of the excretory system?

- Maintenance of the water balance - Elimination of nitrogenous wastes - Production of urine - Maintenance of salt balance

Why is HIV a dangerous pathogen?

- The virus evolves within the body. - It leads to the loss of T cells. - It mutates at a very high rate. - The virus prevents recognition and elimination by the immune system.

Which of the following substances is generally filtered from the blood by the kidneys?

- Urea - Water - Sodium - Glucose

How are the roles of a respiratory pigment and an enzyme similar?

An enzyme speeds up a reaction without changing the equilibrium and without being consumed. Similarly, a respiratory pigment speeds up the exchange of gases between the body and the external environment without changing the equilibrium state and without being consumed.

Which of the following should be the same in identical twins?

the set of MHC molecules produced

In humans, the first line of defense against infection is __________.

the skin and mucous membranes.

What is the physiological cause of a heart attack?

A blood clot lodging in a blood vessel supplying the heart.

Which of the following is an example of a portal vein?

A blood vessel carrying blood from the stomach to the liver

Which of the following would increase the release of oxygen from red blood cells?

A decrease in pH and a decrease in the PO2

What conditions are responsible for the stimulation of the juxtaglomerular apparatus (JGA)?

A decrease in the blood pressure or blood volume in the afferent arteriole (JGA activation results in the release of renin, which converts angiotensinogen to its active form. Angiotensin II then increases blood pressure by vasoconstriction and increased sodium reabsorption.)

What happens when the CO2 level from cellular respiration increases in the blood?

A decrease in the pH of the cerebrospinal fluid triggers the brain's breathing control centers, which stimulate diaphragm and rib muscle contractions.

If an injury tore a small hole in the membranes surrounding your lungs, what effect on lung function would you expect?

A hole would allow air to enter the space between the inner and outer layers of the double membrane, resulting in a condition called a pneumothorax. The two layers would no longer stick together, and the lung on the side with the hole would collapse and cease functioning.

Which of the following statements is not true?

A lymphocyte has receptors for multiple different antigens.

People with herpes simplex type 1 viruses often get mouth sores when they have a cold or similar infection. How might this location benefit the virus?

A person with a cold is likely to produce oral and nasal secretions that facilitate viral transfer. In addition, since sickness can cause incapacitation or death, a virus that is programmed to exit the host when there is a physiological stress has the opportunity to find a new host at a time when the current host may cease to function.

How would a macrophage deficiency likely affect a person's innate and adaptive defenses?

A person with a macrophage deficiency would have frequent infections. The causes would be poor innate responses, due to diminished phagocytosis and inflammation, and poor adaptive responses, due to the lack of macrophages to present antigens to helper T cells.

A recording of the electrical activity of a patient's heart shows that the atria are contracting regularly and normally, but every few beats the ventricles fail to contract. Which of the following is probably functioning improperly?

AV node.

If you had additional hearts distributed throughout your body, what would be one likely advantage and one likely disadvantage?

Additional hearts could be used to improve blood return from the legs. However, it might be difficult to coordinate the activity of multiple hearts and to maintain adequate blood flow to hearts far from the gas exchange organs.

Chambers A and B are separated by a membrane permeable to substance X. The concentration of X is 5% in A and 15% in B. The volume of A is three times that of B. Which of the following will occur?

Although diffusion is random, the result will be the net movement of X from B to A.

Which structure in a human is most similar in function to the gill lamellae of a fish?

Alveoli (In a fish, the actual exchange of oxygen and carbon dioxide occurs at the gill lamellae; these events occur at the alveoli in the human lung.)

Which of the following components of the mammalian gas exchange system has a surface covered by a thin film of fluid without cilia?

Alveoli (The tiniest bronchioles dead-end in tiny air sacs called alveoli, which have a very thin epithelium and no cilia.)

Which of the following is filtered from blood but not normally found in urine?

Amino acids (Amino acids are filtered because they are small, but normally their reabsorption is 100% efficient.)

Most aquatic animals excrete ammonia, whereas land animals excrete urea or uric acid. What is the most likely explanation for this difference?

Ammonia is very toxic, and it takes a lot of water to dilute it. (Because aquatic animals have access to so much water, the ammonia they excrete is diluted without causing harm.)

The fluid that enters vertebrate nephrons is called the filtrate. What is the source of the filtrate?

Blood in capillaries (Filtration occurs as blood pressure forces water, urea, salts, and other small solutes from the blood in the glomerulus into the lumen of Bowman's capsule.)

If while standing you placed your forearm on your head, how, if at all, would the blood pressure in that arm change? Explain.

Blood pressure in the arm would fall by 25-30 mm Hg, the same difference as is normally seen between your heart and your brain.

How do cortical and juxtamedullary nephrons differ with respect to reabsorbing nutrients and concentrating urine?

Both types of nephrons have proximal tubules that can reabsorb nutrients, but only juxtamedullary nephrons have loops of Henle that extend deep into the renal medulla. Thus, only kidneys containing juxtamedullary nephrons can produce urine that is more concentrated than the blood.

Which of the following is an immediate function of histamine?

Causing local swelling of the tissue

Clots in arteries can cause heart attacks and strokes. Why, then, does it make sense to treat people with hemophilia by introducing clotting factors into their blood?

Clotting factors do not initiate clotting but are essential steps in the clotting process.

Which of the following is the main factor that causes lymph to move through lymphatic vessels?

Contractions of body muscles near lymph vessels.

Gas exchange in the gills of a bony fish is maximized by which of the following?

Countercurrent exchange

What is the role of dendritic cells in the primary immune response?

Dendritic cells present antigen to, and thus activate helper T cells. (In response, the T cell proliferates.)

What determines whether O2 and CO2 undergo net diffusion into or out of capillaries? Explain.

Differences in partial pressure between the capillaries and the surrounding tissues or medium; the net diffusion of a gas occurs from a region of higher partial pressure to a region of lower partial pressure.

Why do larger animals, such as a bullfrog, require a circulatory system, while animals such as a planarian do not?

Diffusion is inadequate to move gases through the body surface and into all parts of a larger animal body. However, diffusion alone is sufficient to move gases in and out of the thin body of a planarian.

What is the function of the filtration step in excretory systems?

Filtration produces a fluid for exchange processes that is free of cells and large molecules, which are of benefit to the animal and could not readily be reabsorbed.

In which animal does the circulatory system include a heart and a system of closed vessels?

Fish

Explain how memory cells strengthen the immune response when a pathogen is encountered for a second time.

Generating memory cells ensures both that a receptor specific for a particular epitope will be present and that there will be more lymphocytes with this specificity than in a host that had never encountered the antigen.

What is atherosclerosis?

Hardening of the arteries by accumulation of fatty deposits (This is one of the leading causes of heart attacks.)

Question 41:What causes CO2 in the blood to decrease?

Hyperventilation

If both copies of a light-chain gene and a heavy-chain gene recombined in each (diploid) B cell, how would this affect B cell development and function?

If each B cell produced two different light and heavy chains for its antigen receptor, different combinations would make four different receptors. If any one were self-reactive, the lymphocyte would be eliminated in the generation of self-tolerance. For this reason, many more B cells would be eliminated, and those that could respond to a foreign antigen would be less effective at doing so due to the variety of receptors (and antibodies) they express.

Suppose that a snake handler bitten by a particular venomous snake species was treated with antivenin. Why might the same treatment for a second such bite have a harmful side effect?

If the handler developed immunity to proteins in the antivenin, another injection could provoke a severe immune response.

A patient with which of the following conditions would probably benefit by injections of purified stem cells?

Impaired resistance to infection AIDS Sickle-cell disease Leukemia

How is the flow of hemolymph through an open circulatory system similar to the flow of water through an outdoor fountain?

In both an open circulatory system and a fountain, fluid is pumped through a tube and then returns to the pump after collecting in a pool.

Describe similarities in the countercurrent exchange that facilitates respiration in fish and thermoregulation in geese.

In fish, water passes over the gills in the direction opposite to that of blood flowing through the gill capillaries, maximizing the extraction of oxygen from the water along the length of the exchange surface. Similarly, in the extremities of some vertebrates, blood flows in opposite directions in neighboring veins and arteries; this countercurrent arrangement maximizes the recapture of heat from blood leaving the body core in arteries, which is important for thermoregulation in cold environments.

A drop in blood pH causes an increase in heart rate. What is the function of this control mechanism?

Increased heart rate increases the rate at which CO2-rich blood is delivered to the lungs, where CO2 is removed.

How does myoglobin aid diving mammals such as the Weddell seal?

It allows diving seals to store a considerable amount of oxygen in their muscles.

Which of the following is a characteristic of adaptive immunity?

It has the ability to detect very specific pathogens.

What is the function of the ascending loop of Henle?

It helps maintain the concentration gradient of NaCl in the interstitial fluid, thus increasing water reabsorption. (NaCl diffuses out of the ascending loop of Henle in the inner medulla and is actively transported out in the outer medulla.)

What is unique about blood in pulmonary arteries compared with blood in other arteries?

It is loaded with carbon dioxide.

Which chamber(s) of a human heart receive(s) and pump(s) oxygenated blood?

Left ventricle and left atrium.

Which of the following is part of the inflammatory response?

Local vasodilation (Histamine triggers vasodilation and increased permeability of nearby capillaries; this increased blood flow is what causes redness and fever during an inflammatory response.)

In what ways does innate immunity protect the mammalian digestive tract?

Lysozyme in saliva destroys bacterial cell walls; the viscosity of mucus helps trap bacteria; acidic pH in the stomach kills many bacteria; and the tight packing of cells lining the gut provides a physical barrier to infection.

When searching for a donor for an organ transplant, doctors try to match the __________ of the donor and recipient as closely as possible.

MHC proteins

Which of the following cells are part of the innate, second line of defense?

Macrophages

Question 33:What is the major reason that land-dwelling mammals evolved lungs rather than gills as a primary respiratory organ?

Protecting gas-exchange surfaces from desiccation is difficult in terrestrial environments.

Which excretory system contains structures called flame bulbs that function in filtration?

Protonephridia (Protonephridia, found in flatworms and other invertebrates, contain ciliated flame bulbs that produce filtrate.)

Antibodies are in which class of proteins?

Receptor (Antibodies are antigen-binding immunoglobulins, produced by B cells, which function as the effector in the immune response. They are soluble receptors specific to particular antigens.)

Which choice below describes a function of white blood cells that helps them carry out defensive functions more effectively?

Release of cytokines (Cytokines help recruit and activate lymphocytes.)

What changes in cardiac function might you expect after surgical replacement of a defective heart valve?

Replacement of a defective valve should increase stroke volume. A lower heart rate would therefore be sufficient to maintain the same cardiac output.

When you hold your breath, which of the following blood gas changes leads initially to the urge to breathe again?

Rising carbon dioxide concentration

Which type of organism would have the least chance of long-term survival in the given environment?

Stenohaline animals that move between fresh water and seawater (Stenohaline animals cannot tolerate large fluctuations of external osmolarity.)

Why is the adaptive immune response to an initial infection slower than the innate response?

Sufficient numbers of cells to mediate an innate immune response are always present, whereas an adaptive response requires selection and proliferation of an initially very small cell population specific for the infecting pathogen.

How does the Bohr shift help deliver O2 to very active tissues?

The Bohr shift causes hemoglobin to release more O2 at a lower pH, such as is found in the vicinity of tissues with high rates of cellular respiration and CO2 release.

The heart of a normally developing human fetus has a hole between the left and right atria. In some cases, this hole does not close completely before birth. If the hole weren't surgically corrected, how would it affect the O2 content of the blood entering the systemic circuit?

The O2 content would be abnormally low because some oxygen-depleted blood returned to the right atrium from the systemic circuit would mix with the oxygen-rich blood in the left atrium.

Three-chambered hearts with incomplete septa were once viewed as being less adapted to circulatory function than mammalian hearts. What advantage of such hearts did this viewpoint overlook?

The ability to shut off blood supply to the lungs when the animal is submerged

The antigen-binding sites of an antibody molecule are formed from the molecule's variable regions. Why are these regions described as variable?

The amino acid sequences of these regions vary widely among antibodies from different B cells.

How do antibodies to foreign blood groups come to exist in the body?

The antibodies arise in response to bacterial inhabitants of the body that have epitopes very similar to blood groups and antigens. (A person with type A blood will make antibodies against B-like bacterial epitopes. If type B blood is introduced into the person's system, the preexisting antibodies will cause an immediate and devastating reaction.)

Explain why blood has a higher O2O2 concentration in the pulmonary veins than in the venae cavae, which are also veins.

The pulmonary veins carry blood that has just passed through capillary beds in the lungs, where it accumulated O2O2. The venae cavae carry blood that has just passed through capillary beds in the rest of the body, where it lost O2O2 to the tissues.

Which of the following is the most accurate and comprehensive description of the function of kidneys?

The regulation of body fluid composition (This includes waste molecule elimination in urine but also the regulation of salt and hydrogen ion concentrations in body fluids.)

Sketch a B cell antigen receptor. Label the V and C regions of the light and heavy chains. Where are the antigen-binding sites, disulfide bridges, and transmembrane region located relative to these regions?

The transmembrane regions lie within the C regions, which also form the disulfide bridges. In contrast, the antigen-binding sites are in the V regions.

How do the molecules that activate the vertebrate TLR signal transduction pathway differ from the ligands in most other signaling pathways?

Whereas the ligand for the TLR receptor is a foreign molecule, the ligand for many signal transduction pathways is a molecule produced by the organism itself.

Which of the following is a function of the circulatory system?

Transporting nutrients

Which of the following is a tube that carries urine from the kidneys to the urinary bladder in a mammal?

Ureter (Urine is conveyed to the urinary bladder via the ureter and to the outside of the body via the urethra.)

Which of the following decreases blood pressure?

Vasodilation

Under what environmental conditions does water move into a cell by osmosis?

Water moves into a cell by osmosis when the fluid outside the cells is hypoosmotic (has a lower solute concentration than the cytosol).

At a particular position along a nephron, the osmotic potential of the filtrate is 500 mOsm/L, whereas the surrounding kidney's is 600 mOsm/L. Which of the following is a likely result?

Water will diffuse out of the nephron by osmosis. (For water to move out of the tubule by osmosis, the interstitial fluid bathing the tubule must be hyperosmotic to the filtrate.)

B lymphocytes __________.

multiply and make antibodies that circulate in blood and lymph

The functional units of kidneys are __________.

nephrons

An albatross spending its life hovering over the ocean provides an extreme example of __________, the process by which animals control solute concentrations and balance water gain and loss.

osmoregulation

Secretion of ADH (antidiuretic hormone) from the __________ occurs in response to __________ and causes __________.

pituitary gland; high blood osmolarity; increased permeability to water of a collecting duct (When excessive water loss causes an increase in blood osmolarity, antidiuretic hormone, released by the pituitary, acts on the collecting duct to increase the reabsorption of water.)

Cellular respiration

produces CO2 and ATP.

Alternative RNA splicing

produces multiple proteins from a single coding gene.

Which of the following would not help a virus avoid triggering an adaptive immune response?

producing proteins very similar to those of other viruses

Most of our nitrogen-containing waste products are a result of __________.

protein metabolism

An individual suffering from __________ has irregularly shaped erythrocytes and may suffer from severe pain and organ swelling.

sickle-cell disease

Phagocytosis is best defined as __________.

the cellular ingestion of foreign substances