textbook study break questions

What are the three basic features of animal circulatory systems?

1. a specialized fluid medium for transporting molecules, exemplified by the blood of the vertebrates

2. a muscular heart for pumping the fluid

3. tubular vessels for distributing the fluid pumped by the heart

What is the difference between an open circulatory system and a closed circulatory system? Why do you think humans could not function with an open circulatory system?

In an open circulatory system, there is no distinction between blood and interstitial fluid. Vessels from the heart release hemolymph directly into body spaces and the fluid is subsequently collected and reenters the heart. In a closed circulatory system, blood is channeled in blood vessels leading to and from the heart and is distinct from the interstitial fluid.

In an open circulatory system, most of the fluid pressure generated by the heart dissipates when the blood is released into the body spaces. Consequently, blood flows relatively slowly. Humans could not function as we do with such a system, because we would not be able to distribute oxygen efficiently throughout the body, nor would we be able to eliminate the wastes we produce.

Distinguish among atria, ventricles, arteries, and veins

Atria are chambers of the heart that receive blood returning to the heart. Ventricles are chambers of the heart that pump blood from the heart. Arteries are vessels of circulatory systems that conduct blood away from the heart at relatively high pressure. Veins are vessels of circulatory systems that carry blood back to the heart.

Distinguish among the systemic, pulmocutaneous, and pulmonary circuits.

The systemic circuit of the circulatory system is the circuit from the heart to most of the tissues and cells of the body and back to the heart. The pulmocutaneous circuit goes from the heart to the skin and lungs or gills in amphibians and back to the heart. The pulmonary circuit goes from the heart to the lungs and back to the heart.

Outline the life cycle of an erythrocyte

Erythrocytes originate as pluripotent stem cells in the red bone marrow. In humans and other mammals, they lose their nucleus, cytoplasmic organelles, and ribosomes as they mature, becoming essentially a membrane-bound hemoglobin reservoir that is not capable of protein synthesis. At the end of their lifespan—about 4 months—erythrocytes are engulfed by macrophages, a type of leukocyte, in the spleen, liver, and bone marrow

How does the body compensate for a lower-than-normal level of oxygen in the blood?

Low oxygen content triggers a negative feedback mechanism to increase erythrocytes in the blood. The kidneys are stimulated to synthesize the hormone erythropoietin (EPO), which stimulates stem cells in the bone marrow to increase erythrocyte production. EPO synthesis is stopped when the oxygen content of the blood rises above normal levels.

What are the roles of leukocytes and platelets?

Leukocytes act as the first line of defense against invading organisms, eliminate dead and dying cells from the body, and remove cellular debris. Platelets assist in blood clotting. When blood vessels are damaged, platelets stick to the collagen fibers exposed to leaking blood and recruit other platelets to the site. Eventually a plug forms at the site, sealing off the damaged area.

What are the three basic features of animal circulatory systems?

The three basic features of animal circulatory systems are:

1. a specialized fluid medium for transporting molecules, exemplified by the blood of vertebrates;

2. a muscular heart for pumping the fluid; and

3. tubular vessels for distributing the fluid pumped by the heart.

What is the difference between an open circulatory system and a closed circulatory system? Why do you think humans could not function with an open circulatory system?

In an open circulatory system, there is no distinction between blood and interstitial fluid. Vessels from the heart release hemolymph directly into body spaces and the fluid is subsequently collected and reenters the heart. In a closed circulatory system, blood is channeled in blood vessels leading to and from the heart and is distinct from the interstitial fluid.

In an open circulatory system, most of the fluid pressure generated by the heart dissipates when the blood is released into the body spaces. Consequently, blood flows relatively slowly. Humans could not function as we do with such a system, because we would not be able to distribute oxygen efficiently throughout the body, nor would we be able to eliminate the wastes we produce.

distinguish among atria, ventricles, arteries, and veins

Atria are chambers of the heart that receive blood returning to the heart. Ventricles are chambers of the heart that pump blood from the heart. Arteries are vessels of circulatory systems that conduct blood away from the heart at relatively high pressure. Veins are vessels of circulatory systems that carry blood back to the heart.

Distinguish among the systemic, pulmocutaneous, and pulmonary circuits.

The systemic circuit of the circulatory system is the circuit from the heart to most of the tissues and cells of the body and back to the heart.

The pulmocutaneous circuit goes from the heart to the skin and lungs or gills in amphibians and back to the heart.

The pulmonary circuit goes from the heart to the lungs and back to the heart.

What is the role of each of the four chambers of the mammalian heart in blood circulation?

The right atrium receives blood in the systemic circuit returning to the heart in vessels coming from the entire body, with the exception of the lungs. The right atrium pumps blood into the right ventricle.

The right ventricle receives blood from the right atrium, and pumps it into the pulmonary arteries going to the lungs, beginning the pulmonary circuit.

The left atrium receives blood returning from the lungs in the pulmonary veins, completing the pulmonary circuit. The left atrium pumps this blood into the left ventricle.

The left ventricle pumps the blood received from the left atrium into the aorta, where the blood begins its path in the systemic circuit.

Distinguish between systole and diastole

Systole is the period of contraction and emptying of the heart. Diastole is the period of relaxation and filling of the heart between contractions.

How do neurogenic and myogenic hearts differ?

Neurogenic hearts beat under the control of signals from the nervous system. If the signals cease, this type of heart stops beating. Myogenic hearts maintain a contraction rhythm without signals from the nervous system. In the event of a serious trauma to the nervous system, this type of heart keeps beating.

Describe the electrical events that occur during the cardiac cycle in a mammalian heart.

SA node cells rhythmically depolarize, which initiates waves of contraction that travel over the heart. The resulting electrical signal spreads through the atria, until it reaches the AV node located just above the insulating layer between the atria and the ventricles. This excites the AV node, which then generates an electrical signal that goes to the bottom of the heart via Purkinje fibers in the septum between the two ventricles. The signal then travels upward in branching Purkinje fibers in the walls of the ventricles, inducing a strong wave of contraction beginning at the bottom of the heart and moving upward. The contraction forces blood from the ventricles into the aorta and pulmonary arteries.

How is blood flow through capillary networks controlled?

Blood flow through capillary networks is controlled by contraction of smooth muscles in arterioles and by contraction of precapillary sphincters at the junctions of capillaries and arterioles.

Explain how, in contrast to most body tissues, the brain does not allow exchange of molecules and ions with blood

In most body tissues, there are small spaces between capillary endothelial cells, but in the brain, the capillary endothelial cells are tightly sealed together, forming a blood–brain barrier

Describe the two major mechanisms that drive the exchange of molecules and ions between the capillaries and the interstitial fluid.

The two major mechanisms are diffusion along concentration gradients and bulk flow. Diffusion along concentration gradients occurs both through the spaces between the capillary endothelial cells and through the plasma membranes. The direction of movement of the molecule or ion depends on the concentration gradient. Thus, oxygen and glucose, which are at higher concentrations in the capillaries, diffuse into the interstitial fluid and then into the cells of the tissues. Carbon dioxide, which is at a higher concentration in the interstitial fluid, diffuses into the capillaries.

Bulk flow carries water, ions, and molecules out of the capillaries through the tiny spaces between endothelial cells. Bulk flow is driven by the pressure of the blood, which is higher than the pressure of the interstitial fluid.

Why is it important to regulate arterial blood pressure?

Arterial blood pressure must be regulated within limits to provide sufficient blood flow for the brain and other tissues and to prevent damage to blood vessels, tissues, and organs that would occur at high blood pressures.

What are the three main mechanisms for regulating blood pressure?

The three main mechanisms for regulating blood pressure are:

1. controlling cardiac output (the pressure and amount of blood pumped by the ventricles);

2. controlling the degree of constriction of the blood vessels (mostly the arterioles); and

3. controlling the total blood volume.

How does epinephrine affect blood pressure?

The hormone epinephrine raises blood pressure by increasing the strength and rate of the heart rate, and by stimulating vasoconstriction of arterioles in certain parts of the body.

What is lymph, and how does it enter the lymph capillaries?

Lymph is interstitial fluid, an aqueous solution containing molecules, ions, infecting bacteria, damaged cells, cellular debris, and lymphocytes.

Because the lymph capillaries consist of a single layer of endothelial cells, the lymphatic fluid can enter them at sites where the endothelial cells overlap when the pressure of the interstitial fluid forces the flaps open. The openings produced are large enough for cells to enter.

Compared with vertebrates, most invertebrates:

a) lead more mobile lives.

b) require a higher level of oxygen.

c) have more complex layers of cells.

d) have blood and interstitial fluid mixing directly in body spaces.

e) require faster delivery and greater quantities of nutrients.

d

Which circulatory system description best matches the group(s) of animals?

a) Cephalopod mollusks such as squids and octopuses have open circulatory systems with ventricles that pump blood away from the heart.

b) Fishes have a single-chambered heart with an atrium that pumps blood through gills for oxygen exchange.

c) Amphibians have the most oxygenated blood in the pulmocutaneous circuit and the most deoxygenated blood in the systemic circuit.

d) Amphibians and reptiles use a two-chambered heart to separate oxygenated and deoxygenated blood.

e) Birds and mammals pump blood to separate pulmonary and systemic systems from two separate ventricles in a four-chambered heart.

e

A healthy student from the coastal city of Boston enrolls at a college in Boulder, Colorado, a mile above sea level. An analysis of her blood in her first months at college would show:

a) decreased macrophage activity.

b) increased secretion of erythropoietin by the kidneys.

c) increased signaling ability of platelets.

d) anemia caused by malfunctioning erythrocytes.

e) increased mitosis of leukocytes.

b

A characteristic of blood circulation through or to the heart is that:

a) the superior vena cava conveys blood to the head.

b) the inferior vena cava conveys blood to the right atrium.

c) the pulmonary arteries convey blood from the lungs to the left atrium.

d) the pulmonary veins convey blood into the left ventricle.

e) the aorta branches into two coronary arteries that convey blood from heart muscle.

b

The heartbeat includes:

a) the systole when the heart relaxes and fills.

b) the diastole when the heart contracts and empties.

c) pressure that causes the AV valves to open, filling the ventricles.

d) rising pressure in the ventricles to open the AV valves and close the SL valves.

e) the “lub” sound when the SL valves open and the “dub” sound when the AV valves close.

c

What is responsible for establishing the rate of heart contraction?

a) the sinoatrial (SA) node

b) Purkinje fibers

c) an insulating layer that isolates the SA node from the right atrium

d) the atrioventricular (AV) node

e) neurogenic stimuli from the nervous system

a

Hydrostatic pressure is best described as:

a) the uncoordinated contractions that occur during heart attacks.

b) a premature ventricular contraction that signifies a skipped beat.

c) a high point of pressure called diastolic blood pressure.

d) an arterial vasodilation caused by carbon dioxide.

e) the pressure of blood on the walls of arteries.

e

Characteristics of veins and venules are:

a) thick walls.

b) large muscle mass in the walls.

c) a large quantity of elastin in the walls.

d) low blood volume compared with arteries.

e) one-way valves to prevent backflow of blood.

e

When capillaries exchange substances:

a) red blood cells move through the capillary lumen in double file.

b) blood flow resistance is lower than it is in arteries and veins.

c) water, ions, glucose, and erythrocytes pass freely between blood and tissues.

d) diffusion down a concentration gradient and bulk flow are operating.

e) diffusion is greatest closest to the venules.

d

How do lymphatic vessels and capillaries differ from other vessels and capillaries in the circulatory system?

a) lymph capillaries are larger in diameter than blood capillaries

b) lymph capillary walls contain several layers of endothelial cells, which allows for efficient filtering of lymph

c) lymph vessels are only distributed in specific regions of the body

d) movement of lymph does not require skeletal muscle movement.

e) the lymphatic system moves up to 8L of fluid through the bloodstream daily

a

Distinguish between the roles of the respiratory medium and the respiratory surface in respiratory systems.

The respiratory medium is the environmental source of oxygen and the repository for released CO₂. For aquatic animals, water is the respiratory medium; for terrestrial animals, it is air. The respiratory surface is the layer of epithelial cells between the body and the respiratory medium. Gas exchange occurs across the respiratory surface— O₂ in and CO₂ out of the body. In certain small animals, the body surface itself is the respiratory surface. Among larger animals, aquatic animals use gills, insects use tracheal systems, and terrestrial animals use lungs as the respiratory surface.

What is an advantage of water over air as a respiratory medium? What are two key advantages of air over water as a respiratory medium?

The advantage of water over air as a respiratory medium is that it readily enables the respiratory surface to remain wet at all times. Two key advantages of air over water as a respiratory medium are:

1. there is much more oxygen in air than in water; and

2. air is much less dense and less viscous than water, so significantly less energy is needed to move air over the respiratory surface than to move water

What advantages do gills confer on a water-breathing animal over skin breathing?

The advantages of gills to water-breathing animals over skin breathing are greater efficiency of gas exchange, the ability to live in more diverse habitats, and the potential to achieve a greater body mass.

What is countercurrent exchange, and how is it beneficial for gas exchange?

In countercurrent exchange, the respiratory medium flows in the opposite direction of the blood flow under the respiratory surface. Examples are the flow of water over the gills in sharks, fishes, and some crabs; all these are opposite to the flow of blood. The advantage of this mechanism is that it maximizes the amounts of O₂ and CO₂ exchanged with the respiratory medium.

How does the tracheal system of insects facilitate gas exchange with the cells of the body?

In the tracheal system, fine branches called tracheoles end in tips that are in contact with body cells. The tracheole tips are filled with fluid, and gas exchange occurs through the fluid and the plasma membrane of the body cells in contact with the tips. Air enters the tracheal system through spiracles on the body surface. Movement of air through the tracheal system occurs by muscledriven contractions and expansions of air sacs within the system.

Distinguish between positive pressure breathing and negative pressure breathing in animals with lungs.

In positive pressure breathing, gulping, swallowing, or pumping action forces air into the lungs. In negative pressure breathing, muscular activity expands the lungs, lowering the pressure of air in the lungs and thereby causing air to be pulled inward.

Explain how inhalation and exhalation occur in a mammal at rest.

Contraction of the diaphragm and the external intercostal muscles pulls the ribs upward and outward, expanding the chest and lungs. By this negative pressure mechanism, the air pressure within the lungs is lower than that outside of the body. The higher outside pressure drives air into the lungs, expanding and filling them. Relaxation of the diaphragm and the intercostal muscles reverses the pressure condition, and the elastic recoil of lungs expels the air.

What neurons control ventilation?

Neuron groups in the brainstem control ventilation. The dorsal respiratory group in the medulla consists mostly of neurons for inspiration. When they fire, they stimulate the inspiratory muscles and inspiration occurs; when firing stops, the inspiratory muscles relax and passive expiration occurs. The ventral respiratory group in the medulla consists of neurons for both inspiration and expiration, but neither fires during quiet breathing. When ventilation demands increase, the neurons for expiration fire, stimulating the expiratory muscles resulting in active expiration. Neural connections from the dorsal respiratory group also stimulate the ventral respiratory group to fire the neurons for inspiration, stimulating inspiratory muscles to contract. A network of neurons at the upper end of the ventral respiratory group generates the basic rhythm of ventilation. The ventral respiratory group of neurons in the medulla stimulates inspiration muscles, which establishes the basic rhythm of ventilation. The dorsal respiratory group of neurons in the medulla also stimulates muscles for inspiration, particularly the diaphragm. The pons respiratory group of neurons modulates the effects of the medullary neuron groups to produce smooth inspirations and expirations. Overall, the interactions between the three groups of neurons regulate the rate and depth of ventilation.

What is the role of chemoreceptors in the medulla?

The chemoreceptors in the medulla monitor the cerebrospinal fluid for changes in pH, which is determined by the CO₂ level in the blood. A rise in blood CO₂ level results in a decrease in cerebrospinal fluid pH that is detected by the chemoreceptors which then signal the respiratory groups of neurons in the medulla to increase the rate and depth of ventilation.

Explain the role of hemoglobin in gas exchange.

Hemoglobin is present in red blood cells. O₂ diffuses from alveoli into the plasma solution in the capillaries and then into the red blood cells. In the red blood cells, the O₂ binds to hemoglobin, thereby lowering the partial pressure of O₂ in the plasma. This leads to more O₂ molecules diffusing down the oxygen concentration gradient from alveolar air to blood. The binding of O₂ to hemoglobin is reversible. Further, the affinity of hemoglobin for O₂ increases as the partial pressure of O₂ increases, and vice versa. This property is important for determining the release of O₂ from hemoglobin keyed to tissue requirements.

Why is carbon monoxide potentially lethal?

CO has much greater affinity for hemoglobin than does O₂, and so it displaces O₂ from hemoglobin, reducing the amount of O₂ carried in the blood. Because the brain does not monitor O₂ levels, and other receptors do not respond until blood O₂ levels are critically low, victims can easily lapse into unconsciousness and death.

What are the key evolutionary adaptations that diving mammals use to survive at significant ocean depths?

• More blood per unit body weight than land animals

• Additional red blood cells, many stored in the spleen and released during a dive

• More myoglobin in muscles than land animals

• Slowing of the heart by as much as 90%

• Reduction of blood circulation to internal organs and muscles by up to 95%

• Retention of lactic acid in the muscles with no release into the blood until the animal returns to the surface

Which of the following describes a respiratory medium?

a) the liver of an amphibian, in which the rate of diffusion is high

b) neurons in the human brain, where CO₂ moves from the neurons to the blood

c) the O₂ in the blood of humans

d) epithelial cells of fish that are in contact with the air

e) air and water

e

Which of the following describes a respiratory surface?

a) a surface consisting of multiple layers of epithelial cells

b) the exoskeleton of an insect

c) the nasal passages of a mammal

d) thin surface consisting of a single layer of epithelial cells

e) the outer membrane of a mitochondrion

d

A geothermal HVAC (heating, ventilating, and air conditioning) system air-conditions your house by passing warm air pulled from the house past a continuous flow of cool water pulled from the ground. How this heat exchanger works is analogous to:

a) countercurrent exchange of gases in fish gills.

b) diffusion of O₂ from blood to cells in shark tissues.

c) diffusion of CO₂ from cells to blood in crabs.

d) use of O₂ in cells in insects.

e) excretion of CO₂ from mammalian cells

a

Tracheal systems are characterized by:

a) closed circulatory tubes that move gases.

b) spiracles that move gases between cells and body fluids.

c) body movements that compress and expand air sacs to pump air.

d) positive pressure breathing, which swallows air into the body.

e) negative pressure breathing, which lowers air pressure at the respiratory surfaces.

c

The partial pressure of O₂ in the atmosphere is 160 mm Hg, but when O₂ moves into the blood its partial pressure is one third lower than the atmospheric partial pressure. Which structure is it moving through at this partial pressure?

a) alveoli

b) bronchi

c) bronchioles

d) tracheae

e) pharynges

a

As a speed skater finishes the last lap of a race:

a) her diaphragm and rib muscles contract when she exhales

b) positive pressure brings air into her lungs

c) her lungs undergo an elastic recoil when she inhales.

d) her tidal volume is at vital capacity

e) her residual volume momentarily reaches zero

d

When cerebrospinal fluid pH decreases due to an increase in CO₂ that diffuses from arterial blood:

a) the central chemoreceptors on the medulla surface signal respiratory neurons in the medulla to cause rib muscles to relax, and then to stimulate and contract the intercostal muscles.

b) the central chemoreceptors on the medulla surface signal the respiratory groups of neurons in the medulla to increase the rate and depth of ventilation.

c) the central chemoreceptors on the medulla surface signal smooth muscles in the walls of arterioles in the lungs to contract.

d) the peripheral chemoreceptors send signals to increase the ventilation rate.

e) the pons respiratory group of neurons sends signals to smooth inspirations and expirations

b

Oxygen enters the blood in the lungs because relative to alveolar air:

a) the CO₂ concentration in the blood is high.

b) the CO₂ concentration in the blood is low.

c) the O₂ concentration in the blood is high.

d) the O₂ concentration in the blood is low.

e) the process is independent of gas concentrations in the bloods

d

A hemoglobin O₂ dissociation curve:

a) demonstrates that hemoglobin is about 50% saturated in the alveoli.

b) shifts to the left when pH rises.

c) demonstrates that hemoglobin holds less O₂ when the pH is higher.

d) illustrates that oxygen saturation is not dependent on CO₂ levels.

e) demonstrates why hemoglobin can bind O₂ at high pH in the lungs and release it at lower pH in the tissue

e

The majority of CO₂ in the blood:

a) is in the form of carbonic acid and bicarbonate ions

b) dissociates to add H+ to the blood to raise its pH to 7.4

c) has a lower P_CO2 than the P_CO2 in the alveolar air.

d) increases in the lung capillaries, which have a higher pH than the tissue capillaries.

e) can be displaced on the hemoglobin molecule by CO if CO is inhaled

a

Define the terms osmosis, osmolarity, hypoosmotic, osmoregulator, and transport epithelium

Osmosis - a process in which water molecules move across a selectively permeable membrane from a region where they are more highly concentrated to one where they are less highly concentrated

Osmolarity - the total solute concentration of a solution. Osmolarity is measured in osmoles per liter of solution, where an osmole is the number of solute molecules and ions (in moles).

A solution that is hypoosmotic has lower osmolarity than the solution on the other side of a selectively permeable membrane. The solution with the higher osmolarity is said to be hyperosmotic.

An osmoregulator is an animal that uses an active control mechanism to keep the osmolarity of cellular and extracellular fluids the same. This osmolarity value may differ from the osmolarity of the surroundings.

Tubules that carry out osmoregulation and excretion are formed from transport epithelium, a layer of cells with specialized transport proteins in their plasma membranes that move specific molecules and ions into and out of the tubule.

Outline the four-step process excretory tubules use in osmoregulation and excretion.

In filtration, water and a number of solutes move nonselectively into the proximal end of the tubules through spaces between cells. In tubular reabsorption, some molecules and ions move selectively from the lumen of the tubule back into the ECF and blood. In tubular secretion, specific small molecules and ions are transported selectively from the ECF and blood into the tubules. In excretion, urine, which contains waste materials, is released from the distal end of the tubule.

How are protonephridia, metanephridia, and Malpighian tubules different? In which animal groups are each of these excretory tubules found?

Protonephridia are found in flatworms and larval mollusks. They are the simplest invertebrate excretory tubules. Body fluids enter the end of protonephridia and are moved through the tubule by movement of cilia on the flame cells. As the fluids move through the protonephridia, some molecules and ions are reabsorbed, and others, including nitrogenous wastes, are secreted into the tubules. Excess fluid is released through pores connecting the network of protonephridia to the body surface.

Metanephridia are found in annelids and most adult mollusks. Body fluids enter the funnel-like proximal end, driven by cilia surrounding that end. Some molecules and ions are reabsorbed as the fluids move through the tubule, and other ions and nitrogenous wastes are secreted into the tubule and excreted from the body surface.

Malpighian tubules are found in insects and other arthropods. Body fluids enter the tubules through spaces between the tubule cells. The distal ends of the tubules empty into the gut. Pressure is not used in the filtration step in Malpighian tubules. The secretion of K⁺ from the hemolymph into the lumen draws in Cl^- . The accumulation of KCl causes water to enter the tubule from the hemolymph by osmosis. Organic wastes now are secreted into the tubule. When the fluids reach the hindgut and rectum, K⁺ and Cl^- are reabsorbed, followed by water. As water leaves, uric acid precipitates as crystals that are excreted from the rectum in the feces.

Describe the structure of a human nephron from the proximal end to the distal end.

At the proximal end, a human nephron forms a cuplike region called Bowman’s capsule. Bowman’s capsule surrounds the glomerulus, a complex of blood capillaries. The capsule and the glomerulus are located in the renal cortex. The proximal convoluted tubule descends in a U-shaped bend called the loop of Henle into the renal medulla, and ascends again to form the distal convoluted tubule. Up to eight distal convoluted tubules drain into one collecting duct

The urine entering the collecting ducts at the end of the nephron has an osmolarity essentially the same as that of fluids in other parts of the body. How is the urine subsequently made more concentrated?

the collecting ducts are permeable to water but not to salt ions. The ducts, which begin in the cortex and descend into the medulla of the kidney, become surrounded by an ever-increasing solute concentration. As the urine passes down the collecting ducts, water moves osmotically out of the ducts, causing the concentration of the urine to increase. At the bottom of the collecting ducts, the urine is about four times more concentrated than other body fluids.

Outline the roles of the RAAS and ADH system in regulating mammalian kidney function.

The RAAS compensates for excessive loss of salt and body fluids. The ADH system compensates for excessive water intake or loss. Combined, the two systems play an important role in regulating the interactions between the kidneys and the rest of the body.

The RAAS is activated when the Na+ concentration of body fluids falls, causing the volume of extracellular fluids and blood pressure also to drop. Cells in the juxtaglomerular apparatus secrete renin, which activates angiotensinogen to produce angiotensin I. Angiotensin-converting enzyme converts angiotensin I to angiotensin II, which has three effects:

1. It constricts arterioles around the body, thereby quickly increasing blood pressure;

2. it stimulates the secretion of aldosterone from the adrenal cortex, which increases Na+ reabsorption in the kidneys and raises the osmolarity of body fluids; as a result, water moves from the tubules into the interstitial fluid, conserving water; and

3. it stimulates thirst so that more water is brought into the body.

The RAAS is suppressed if the NaCl concentration in body fluids is higher than normal.

In the ADH system, ADH is released from the posterior pituitary when osmoreceptors in the hypothalamus detect an increase in the osmolarity of body fluids. ADH increases water reabsorption from the distal convoluted tubules and collecting ducts of the kidney; as a result, urinary output is reduced and water is conserved. In the case of a decrease in osmolarity, ADH release from the pituitary is inhibited, thereby decreasing water reabsorption in the kidney.

How do marine and freshwater teleosts differ in water, salt, and nitrogenous-waste regulation?

Marine teleosts live in seawater, which is hyperosmotic to their body fluids. They drink seawater continuously to replace water lost to the environment by osmosis. Na+ , K+ , and Cl- ions from the seawater they drink are excreted by the gills. Nitrogenous wastes are released from the gills, primarily as ammonia, by simple diffusion.

Freshwater fishes live in fresh water, which is hypoosmotic to their body fluids. They take in water by osmosis and excrete excess water. Salts needed for bodily functions are obtained from food and by active transport through the gills from the water. Nitrogenous wastes are excreted from the gills as ammonia

Reptiles and birds excrete nitrogenous wastes in the form of uric acid. Is there an advantage to doing this as opposed to the mammalian process of excreting nitrogenous wastes as urea?

The excretion of urea in mammals involves expelling the urea in solution—urine. Thus, there is loss of water with excretion of nitrogenous waste as urea. Excretion of nitrogenous waste in the form of uric acid conserves water because uric acid crystals are almost water-free

Distinguish between ectothermy and endothermy. Give one advantage and one disadvantage for each form of thermoregulation.

Ectothermy applies to animals that obtain heat energy primarily from the environment; endothermy applies to animals that obtain heat energy primarily from internal reactions. Generally speaking, ectotherms are highly successful in warm environments, but their bodily functions slow down as the temperature drops. Endotherms remain active over a broader range of environmental temperatures than ectotherms do, but they require an almost constant supply of energy to maintain their body temperature

Describe two mechanisms an ectothermic animal can use to regulate its temperature.

The thermoregulatory responses shown by ectotherms can be physiological, such as regulating blood flow to internal organs or to the skin, or behavioral, such as physically moving to a location in the environment suitable for their heat energy needs at the time

What is thermal acclimatization?

Thermal acclimatization refers to the physiological changes that many ectotherms make to compensate for seasonal shifts in environmental temperature

Describe how thermoreceptors and negative feedback pathways achieve temperature regulation in endotherms.

Temperature regulation in endothermic animals involves mechanisms that balance internal heat production against heat loss from the body. Internal heat production is controlled by negative feedback pathways triggered by thermoreceptors in the skin, the hypothalamus, and the spinal cord. When a deviation from the set point occurs, this system operates to return the core temperature to that set point through changes in metabolic processes, behavioral activities, and control of heat loss at the skin surface.

Which of the following statements about osmoregulation is true?

1. In freshwater invertebrates, salts move out of the body into the water because the animal is hypoosmotic to the water.

2. A marine teleost has to fight gaining water because it is isoosmotic to the sea.

3. Most land animals are osmoconformers.

4. Vertebrates are usually osmoregulators.

5. Terrestrial animals can regulate their osmolarity without expending energy

4

One role of tubules in excretion is to:

a) absorb H⁺ ions to buffer body fluids.

b) tranport proteins across the transport epithelium

c) reabsorb glucose and amino acids

d) move toxic substances from the filtrate into the cells composing the transport tubules.

e) filter by maintaining a lower pressure in the fluid outside the tubule than inside it.

c

Products of metabolism in humans, as in:

1. terrestrial amphibians, can include urea, which requires more energy to produce than ammonia.

2. birds and reptiles, can include uric acid, which is nontoxic and excreted as a paste.

3. sharks, are primarily excreted as ammonia.

4. hydra, must be isoosmotic with the water ingested.

5. other mammals, cannot include water as water comes only from what they drink

1

A mammalian nephron contains the:

a) Bowman’s capsule, which delivers the filtrate to the glomerulus.

b) Bowman’s capsule, which filters fluids, 99% of which will be excreted.

c) proximal convoluted tubule, which moves Na⁺and K⁺ into the filtrate of the interstitial fluids

d) proximal convoluted tubule, which reabsorbs K⁺, Na⁺, Cl^-, and H₂O.

e) proximal convoluted tubule, which lacks microvilli to ease fluid movement through it

d

Which of the following correctly describes a part of kidney function?

1. Collecting ducts dilute urine because they are permeable to salt but not water.

2. In the ascending loop of Henle, Na+ and Cl+ move into the tubules because the osmolarity of the filtrate is increased.

3. The descending loop of Henle receives filtrate from the ascending loop.

4. The distal convoluted tubule pumps water into the tubule by active transport.

5. The renal pelvis receives urine from the collecting ducts and carries it to the ureters

5

Which of the following is an example of autoregulation of kidney function?

1. The RAAS regulates Na+ by secreting renin when blood pressure or blood volume decreases.

2. The ADH system regulates water balance by decreasing water reabsorption and increasing excretion of salt.

3. Receptors in the juxtaglomerular apparatus detect a higher salt concentration in the distal convoluted tubule and trigger constriction of the afferent arteriole to reduce glomerular filtration rate.

4. ANF is released by the kidney to increase renin release.

5. Angiotensin II lowers blood pressure by constricting arterioles.

3

Deficient water levels in humans are prevented by:

1. osmoreceptors in the hypothalamus that detect decreases in salt concentrations.

2. the hypothalamus stimulating the posterior pituitary to secrete a hormone that allows the collecting ducts and distal convoluted tubules to be permeable to water.

3. inhibiting ADH, which causes a rise in osmolarity of the ECF.

4. producing dilute urine.

5. drinking alcohol, which stimulates aldosterone to raise the osmolarity of body fluids

2

Which best exemplifies ectothermy?

a) The metabolic rate increases as the temperature decreases.

b) Body temperature remains constant when environmental temperatures change.

c) Food demand increases when temperatures drop.

d) Virtually all invertebrate groups are ectotherms.

e) No vertebrate groups are ectotherms

d

Unique to endotherms is:

1. torpor.

2. thermal acclimatization.

3. a nonchanging body temperature.

4. response to seasonal temperature changes.

5. thermoregulation by a hypothalamus

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