Question 1
What is meant by homeostasis?
A.
Maintenance of internal conditions within preset limits despite fluctuations
B.
Conversion of chemical energy into heat to increase enzyme activity
C.
Maintenance of external conditions at a constant value by behaviour
D.
Removal of toxic metabolic waste products from the blood plasma
Question 2
A homeostatic variable falls below its set point. What is the usual effect of negative feedback?
A.
Responses are activated that raise the variable towards the set point.
B.
The receptor becomes the effector until the variable is stable.
C.
Responses are activated that lower the variable further from the set point.
D.
The set point is permanently reduced to match the new value.
Question 3
Blood glucose concentration rises after a carbohydrate-rich meal. What sequence is part of the normal homeostatic response?
A.
Beta cells secrete glucagon, causing glycogen breakdown in skeletal muscle.
B.
Beta cells secrete insulin, causing increased glucose uptake by target cells.
C.
Alpha cells secrete insulin, causing liver cells to release glucose.
D.
Alpha cells secrete glucagon, causing adipose cells to absorb less glucose.
Question 4
Core body temperature falls below the set point. What role does the hypothalamus have in thermoregulation?
A.
It secretes thyroxin directly into the blood to decrease metabolic rate.
B.
It acts as an insulating effector by storing lipid under the skin.
C.
It integrates temperature information and initiates responses that increase heat production.
D.
It increases heat loss by causing arterioles in the skin to dilate.
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Question 5
Which row correctly distinguishes osmoregulation from excretion in the kidney?
| Osmoregulation | Excretion | |
|---|---|---|
| A | Regulation of osmotic concentration of body fluids | Removal of toxic metabolic waste products |
| B | Removal of urea from blood plasma only | Regulation of blood glucose concentration |
| C | Secretion of digestive enzymes into ducts | Removal of excess oxygen from blood |
| D | Maintenance of external water availability | Storage of useful solutes in the nephron |
A.
Regulation of osmotic concentration of body fluids | Removal of toxic metabolic waste products
B.
Removal of urea from blood plasma only | Regulation of blood glucose concentration
C.
Secretion of digestive enzymes into ducts | Removal of excess oxygen from blood
D.
Maintenance of external water availability | Storage of useful solutes in the nephron
Question 6
What adaptation of cells in the proximal convoluted tubule supports selective reabsorption of glucose and amino acids?
A.
Contractile fibres that pump filtrate through Bowman’s capsule
B.
Many mitochondria supplying ATP for active transport processes
C.
A thick waxy cuticle preventing solutes from leaving the filtrate
D.
Large gaps that allow blood cells to move into the tubule lumen
Question 7
Homeostasis involves control of conditions in the internal environment of a multicellular organism.
Define homeostasis.
[1]
Outline why blood pH and blood glucose concentration are regulated homeostatically.
[2]
Question 8
The kidney has roles in both osmoregulation and excretion.
Distinguish between osmoregulation and excretion.
[2]
State the units used for osmotic concentration.
[1]
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Question 9
The graph shows blood glucose concentration during a glucose tolerance test in two individuals, X and Y. Individual X has a lower starting concentration, a smaller peak and a faster return towards the starting concentration than individual Y.
What is the best interpretation of individual Y's response?
A.
Individual Y has type 1 diabetes because glucagon secretion is absent.
B.
Individual Y is unaffected because blood glucose always rises after glucose intake.
C.
Individual Y may have diabetes because blood glucose remains elevated for longer.
D.
Individual Y has type 2 diabetes because beta cells are destroyed by autoimmunity.
Question 10
A person is in hot air with very high humidity. Sweat production is high but cooling is less effective than in dry air at the same temperature.
What explains the reduced cooling?
A.
Hair erection traps humid air and prevents all heat exchange.
B.
Less sweat evaporates, so less heat is removed from the skin.
C.
More sweat evaporates, so less heat is carried away by the blood.
D.
Vasoconstriction increases blood flow through skin capillaries.
Question 11
A urine test detects a large plasma protein in the urine of a patient. Damage to which structure would most directly explain this result?
A.
Ascending limb cells that actively transport ions
B.
Collecting duct cells that insert aquaporins after ADH binds
C.
Cells of the proximal convoluted tubule that cotransport glucose
D.
Filtration barrier of the glomerulus and Bowman’s capsule
Question 12
What is the role of active transport of ions in the ascending limb of the loop of Henle?
A.
It makes the ascending limb permeable to water, diluting the medulla.
B.
It increases osmotic concentration in the medulla, facilitating water reabsorption from collecting ducts.
C.
It removes all urea from the filtrate before it reaches Bowman’s capsule.
D.
It causes glucose to be reabsorbed from the collecting duct into the blood.
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Question 13
A person has a high blood osmotic concentration after prolonged sweating without drinking water. What change is expected in the collecting ducts?
A.
Active transport of glucose from the collecting duct increases blood osmotic concentration.
B.
Aquaporins are removed into vesicles, producing a larger volume of dilute urine.
C.
Podocyte slit gaps widen, allowing more water to enter Bowman’s capsule.
D.
More aquaporins are inserted into cell surface membranes, increasing water reabsorption.
Question 14
The diagram shows the general organization of a homeostatic control system.
State the role of a receptor in a negative feedback loop.
[1]
Explain why negative feedback, rather than positive feedback, is used to maintain homeostasis.
[2]
Question 15
A person moves from a warm room into a cold outdoor environment.
State the brain region that integrates temperature information for thermoregulation.
[1]
Explain how thyroxin can contribute to raising core body temperature.
[2]
State one effector tissue involved in heat production in cold conditions.
[1]
Question 16
A participant sat in a chamber in which the air temperature was changed. Core body temperature and skin temperature were recorded.
Identify the variable in the graph that is most tightly regulated.
[1]
State one reason why maintaining this variable within preset limits is important for cells.
[1]
Explain how the data illustrate homeostasis.
[2]
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Question 17
Skin blood flow and sweat production were measured in volunteers while core body temperature was raised gradually by exercise in a warm room.
Describe the change in skin blood flow as core body temperature rises above the set point.
[1]
Explain how the change in skin blood flow helps reduce core body temperature.
[2]
State how sweating cools the body.
[1]
Question 18
The table shows changes in the composition of plasma and urine in two people after different treatments.
Treatment | Plasma osmotic concentration / mosmol L | Urine volume / L day | Urine osmotic concentration / mosmol L | Urea excretion / mmol day |
|---|---|---|---|---|
Control | 290 | 1.4 | 900 | 28 |
High water intake | 282 | 6.2 | 120 | 27 |
High protein intake | 291 | 1.5 | 880 | 76 |
Identify the treatment that provides stronger evidence for osmoregulation.
[1]
Distinguish osmoregulation from excretion using the data.
[2]
State the SI-derived unit used for osmotic concentration in the table.
[1]
Question 19
The table shows percentage change in blood flow to organs during vigorous exercise compared with wakeful rest.
| Organ | Percentage change in blood flow |
|---|---|
| Skeletal muscle | large positive change |
| Gut | negative change |
| Kidney | negative change |
| Brain | small positive change |
What is the best explanation for this pattern?
A.
Blood flow to kidneys increases to raise filtration rate during exercise.
B.
Blood flow to the gut increases to speed digestion during exercise.
C.
All organs receive the same maximum blood flow when cardiac output increases.
D.
Blood flow is redistributed to meet high ATP demand in muscles while maintaining brain supply.
Question 20
After a meal, blood glucose concentration rises above the regulated range.
State the pancreatic endocrine cells that secrete insulin.
[1]
Explain how insulin lowers blood glucose concentration after a meal.
[3]
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Question 21
Type 1 diabetes and type 2 diabetes both affect control of blood glucose concentration.
Distinguish between the physiological changes that cause type 1 diabetes and type 2 diabetes.
[2]
Compare one treatment or prevention method for each type of diabetes.
[2]
Question 22
In hot conditions, humans use several mechanisms to increase heat loss from the body.
Explain how vasodilation of arterioles in the skin increases heat loss.
[2]
Explain why sweating may be less effective at cooling the body in very humid air.
[2]
Question 23
The diagram shows the renal corpuscle at the start of a nephron.
Explain how high pressure is produced in the glomerulus.
[1]
Explain how the filtration barrier allows ultrafiltration but retains blood cells and most plasma proteins.
[3]
Question 24
The proximal convoluted tubule modifies glomerular filtrate before it reaches the loop of Henle.
Outline selective reabsorption in the proximal convoluted tubule.
[3]
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Question 25
The loop of Henle contributes to the ability of mammals to produce concentrated urine.
State the process carried out by cells of the ascending limb that maintains a high osmotic concentration in the medulla.
[1]
Explain how the loop of Henle facilitates water reabsorption in the collecting duct.
[3]
Question 26
Blood glucose, plasma insulin and plasma glucagon were measured in a healthy adult after a meal and during a later fasting period.
Describe the relationship between blood glucose concentration and plasma insulin concentration after the meal.
[2]
State the pancreatic endocrine cells that secrete glucagon.
[1]
Explain how glucagon secretion helps restore blood glucose concentration during fasting.
[2]
Question 27
Three adults completed an oral glucose tolerance test. Each drank the same glucose solution after an overnight fast.
Identify the participant whose results are most typical of an unaffected person.
[1]
Outline the evidence from the graph that participant B may have diabetes mellitus.
[2]
Suggest one physiological difference that could distinguish type 1 diabetes from type 2 diabetes in a further test.
[1]
Question 28
Samples were taken from blood plasma, Bowman’s capsule and the end of the proximal convoluted tubule in a mammalian nephron.
Substance | Blood plasma / % | Bowman's capsule / % | End of PCT / % |
|---|---|---|---|
Glucose | 100 | 100 | 0 |
Plasma proteins | 100 | 0 | 0 |
Identify one component in blood plasma that should not normally enter Bowman’s capsule in significant amounts.
[1]
Explain why glucose is present in Bowman’s capsule but absent or almost absent at the end of the proximal convoluted tubule.
[2]
Explain one adaptation of proximal convoluted tubule cells for selective reabsorption.
[2]
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Question 29
Blood flow to four organs was measured in the same adult during wakeful rest, vigorous exercise and sleep.
Organ | Wakeful rest / | Vigorous exercise / | Sleep / |
|---|---|---|---|
Skeletal muscle | 1.2 | 8.0 | 0.6 |
Gut | 1.1 | 0.4 | 1.0 |
Brain | 0.8 | 0.8 | 0.7 |
Kidney | 1.2 | 0.8 | 0.9 |
Identify the organ with the greatest increase in blood flow during vigorous exercise compared with wakeful rest.
[1]
Suggest why blood flow to the gut decreases during vigorous exercise.
[2]
Explain how arterioles control the changes in blood supply shown in the table.
[2]
Question 30
A person loses water during prolonged exercise without drinking. Blood osmotic concentration rises above the regulated range.
State where the change in blood osmotic concentration is detected.
[1]
Explain how antidiuretic hormone changes water reabsorption in the collecting ducts in this situation.
[3]
Question 31
During vigorous exercise, blood flow to a person’s skeletal muscles increases from at wakeful rest to . Blood flow to the gut decreases over the same period.
Organ | Wakeful rest / | Vigorous exercise / |
|---|---|---|
Skeletal muscles | 1.2 | 18.0 |
Gut | 1.0 | 0.4 |
Calculate the percentage increase in blood flow to the skeletal muscles from wakeful rest to vigorous exercise.
[2]
Suggest why blood flow to skeletal muscles and the gut changes in opposite directions during vigorous exercise.
[2]
Question 32
A simplified model of thermoregulation during exposure to cold is shown.
State the role of the hypothalamus in the model.
[1]
Explain how the pituitary gland and thyroid gland can contribute to restoring body temperature.
[2]
Explain why this is an example of negative feedback rather than positive feedback.
[2]
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Question 33
Volunteers exercised at the same intensity in two environments with the same air temperature but different relative humidity. Sweat production, sweat evaporation and core body temperature were recorded.
Time / min | Sweat production rate, low RH / mL min | Sweat production rate, high RH / mL min | Sweat evaporation rate, low RH / mL min | Sweat evaporation rate, high RH / mL min | Core body temperature, low RH / | Core body temperature, high RH / |
|---|---|---|---|---|---|---|
0 | 0 | 0 | 0 | 0 | 37.0 | 37.0 |
10 | 8 | 8 | 7 | 3 | 37.1 | 37.3 |
20 | 11 | 12 | 10 | 4 | 37.2 | 37.6 |
30 | 13 | 14 | 12 | 5 | 37.4 | 38.0 |
Compare sweat production in the two environments.
[1]
Explain why core body temperature increases more in the high-humidity environment.
[2]
Evaluate the statement that sweat production rate alone is a reliable measure of cooling effectiveness.
[2]
Question 34
Osmotic concentration was measured in different regions of the kidney medulla and in filtrate at positions along the loop of Henle.
Region | Depth below cortex / mm | Medulla / mOsm kg | Filtrate / mOsm kg |
|---|---|---|---|
Cortex, start of descending limb | 0 | 300 | 300 |
Outer medulla, descending limb | 2 | 500 | 500 |
Inner medulla, descending limb | 4 | 800 | 800 |
Deep medulla, bend of loop | 6 | 1200 | 1200 |
Inner medulla, ascending limb | 4 | 800 | 700 |
Outer medulla, ascending limb | 2 | 500 | 300 |
Cortex, end of ascending limb | 0 | 300 | 100 |
Describe the change in osmotic concentration of the medulla with depth.
[1]
Explain how the ascending limb of the loop of Henle contributes to the medullary gradient.
[2]
Suggest why a steep medullary gradient is useful when antidiuretic hormone is present.
[2]
Question 35
A volunteer was deprived of water for several hours and then allowed to drink water. Blood osmotic concentration, plasma antidiuretic hormone and urine output were monitored.
Time / h | Condition | Blood osmotic concentration / | Plasma ADH / | Urine output / |
|---|---|---|---|---|
0 | before deprivation | 285 | 2 | 90 |
2 | deprivation | 288 | 3 | 70 |
4 | deprivation | 292 | 5 | 40 |
6 | deprivation | 297 | 8 | 15 |
8 | after drinking water | 289 | 4 | 60 |
10 | after drinking water | 285 | 2 | 90 |
Describe the relationship between blood osmotic concentration and antidiuretic hormone concentration during water deprivation.
[1]
Explain how the change in antidiuretic hormone concentration affects collecting duct cells.
[2]
Explain why urine output changes during water deprivation.
[2]
Question 36
A volunteer drinks a glucose solution after fasting overnight. Blood glucose concentration and plasma concentrations of pancreatic hormones are monitored for the next two hours.
I.
State the pancreatic endocrine cell type that secretes insulin.
[1]
II.
Outline why insulin concentration changes after the glucose solution is drunk.
[2]
Explain how insulin lowers blood glucose concentration.
[3]
Discuss why this response is an example of negative feedback rather than positive feedback.
[2]
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Question 37
A patient is admitted to hospital with severe diarrhoea and fever. Blood tests show changes in blood pH, blood glucose concentration and blood osmotic concentration.
I.
Define homeostasis.
[1]
II.
State the immediate internal environment of most body cells in a multicellular animal.
[1]
Explain why blood pH and core body temperature must be regulated within narrow limits.
[2]
Suggest why severe diarrhoea can disturb blood osmotic concentration and why this threatens cells.
[2]
Question 38
Researchers tested a drug that blocks insertion of aquaporins into the membranes of collecting duct cells. Participants had controlled water intake and were given antidiuretic hormone with or without the drug.
Treatment | Urine volume / mL day | Urine osmotic concentration / mOsm kg |
|---|---|---|
No ADH, no drug | 1500 | 300 |
ADH, no drug | 500 | 1200 |
ADH + drug | 1200 | 500 |
Describe the effect of added antidiuretic hormone on urine volume in the absence of the drug.
[1]
Explain the effect of the drug on urine osmotic concentration.
[2]
Evaluate whether the data support the conclusion that ADH acts mainly by changing aquaporin location rather than by changing the medullary osmotic gradient.
[2]
Question 39
Two groups of runners complete the same race at the same air temperature. One race is held in dry air and the other in humid air. Mean core body temperature and sweat loss are recorded.
Time / min | Core temp dry / | Core temp humid / | Sweat loss dry / L | Sweat loss humid / L |
|---|---|---|---|---|
0 | 37.0 | 37.0 | 0.0 | 0.0 |
15 | 37.2 | 37.5 | 0.3 | 0.4 |
30 | 37.6 | 38.1 | 0.7 | 0.9 |
45 | 37.9 | 38.6 | 1.0 | 1.4 |
60 | 38.2 | 39.1 | 1.4 | 2.0 |
I.
Identify the integrating centre for thermoregulation in humans.
[1]
II.
State one type of receptor involved in detecting temperature change.
[1]
Explain two physiological responses that increase heat loss when core body temperature rises.
[3]
Evaluate why humid conditions are more likely to cause dangerous overheating, even when sweating is increased.
[2]
Question 40
An oral glucose tolerance test is carried out on two adults. Adult A has a healthy body mass and exercises regularly. Adult B has prolonged obesity and low physical activity.
I.
Describe the evidence from the graph that Adult B has impaired blood glucose regulation.
[2]
II.
State the most likely type of diabetes suggested by Adult B's risk factors.
[1]
Compare the physiological changes that form the basis of type 1 and type 2 diabetes.
[3]
Discuss prevention and treatment approaches for Adult B.
[2]
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Question 41
A teacher uses two models to explain feedback. In model X, a rise in a variable causes responses that reduce the rise. In model Y, a rise in a variable causes responses that increase the rise further.
I.
Identify which model represents negative feedback.
[1]
II.
State one component of a homeostatic feedback loop that compares a detected value with the set point.
[1]
Compare and contrast negative and positive feedback in relation to homeostasis.
[3]
Apply the negative feedback model to regulation of blood glucose when blood glucose falls below the set point.
[2]
Question 42
The figure shows part of a nephron and its associated blood vessels. A sample of blood plasma, glomerular filtrate and urine is analysed for cells, proteins, glucose and urea.
I.
Identify the structure where ultrafiltration occurs.
[1]
II.
Outline two features of the filtration barrier that allow ultrafiltration while retaining cells and most proteins.
[2]
Explain how high pressure is generated in the glomerulus and how Bowman’s capsule collects filtrate.
[2]
Explain how cells of the proximal convoluted tubule are adapted for selective reabsorption.
[3]
Question 43
A patient with kidney disease has reduced filtration rate and abnormal urine composition. A doctor explains that the kidneys are involved in both excretion and osmoregulation.
I.
Distinguish between excretion and osmoregulation.
[2]
II.
State one nitrogenous waste excreted by mammalian kidneys.
[1]
Explain why useful substances must be reabsorbed after ultrafiltration.
[2]
Evaluate the consequences of reduced kidney function for the internal environment.
[2]
Question 44
Blood flow to selected organs is measured in the same adult during wakeful rest, vigorous exercise and sleep.
I.
Define cardiac output.
[1]
II.
State the type of blood vessel that mainly adjusts blood supply to organs.
[1]
Explain why skeletal muscle blood supply changes during vigorous exercise.
[2]
Compare and contrast the pattern of blood supply to the gut, kidneys and brain during exercise and sleep.
[4]
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Question 45
Newborn babies have a high surface area relative to volume and may cool rapidly after birth. Medical staff dry the baby, wrap it and monitor core temperature.
I.
State the normal approximate human core body temperature set point.
[1]
II.
Outline the role of peripheral and central thermoreceptors in detecting cooling.
[2]
Explain how the hypothalamus, pituitary gland and thyroxin can contribute to warming the body.
[2]
Discuss the roles of muscle and adipose tissue as effectors of temperature change in a newborn.
[2]
Question 46
A person walks for several hours in hot dry conditions without drinking. Blood osmotic concentration and urine volume are monitored before and after the walk.
Measure | Before walk | After walk |
|---|---|---|
Blood osmotic concentration / mOsmol L | 285 | 300 |
Urine volume / cm | 1400 | 400 |
I.
Define osmoregulation.
[1]
II.
State the units used for osmotic concentration.
[1]
Explain how the hypothalamus and pituitary gland respond to the change in blood osmotic concentration.
[2]
Discuss how the loop of Henle and ADH act together to conserve water.
[4]
Question 47
A drug blocks ADH receptors on collecting duct cells. A patient taking the drug produces a large volume of dilute urine even when water intake is low.
I.
State the gland that releases ADH into the blood.
[1]
II.
State the target cells affected by ADH in the nephron.
[1]
Explain the normal effect of ADH on aquaporins and water reabsorption.
[3]
Evaluate why the drug causes a large volume of dilute urine and predict its effect on blood osmotic concentration if water is not replaced.
[3]
Question 48
Two mammal species are compared. Species A lives in freshwater habitats and produces dilute urine. Species B lives in arid habitats and produces highly concentrated urine. Both species have nephrons with loops of Henle and collecting ducts.
I.
Identify the limb of the loop of Henle in which sodium ions are actively transported out of the filtrate.
[1]
II.
Outline why water does not follow sodium ions out of this limb.
[2]
Explain how a high osmotic concentration in the medulla facilitates water reabsorption in collecting ducts.
[2]
Discuss why Species B can produce more concentrated urine than Species A, including the role of ADH.
[3]
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