D3.3 Homeostasis
Practice exam-style IB Biology questions for Homeostasis, aligned with the syllabus and grouped by topic.
Question 1
What is meant by homeostasis?
A.
Maintenance of the internal environment within limits despite fluctuations
B.
Production of energy by all cells at a constant rate
C.
Maintenance of the external environment at a constant value
D.
Movement of substances across membranes down concentration gradients
Question 2
Which variable is a homeostatic variable in humans?
A.
Blood osmotic concentration
B.
Number of red blood cells in one capillary
C.
Hair length
D.
Lung volume after a deep breath
Question 3
A homeostatic variable rises above its set point. What feature of negative feedback restores the variable?
A.
The receptor stops detecting changes in the variable
B.
The response reduces the original increase
C.
The response amplifies the original increase
D.
The set point changes to match the new value
Question 4
What is the effect of insulin on blood glucose concentration?
A.
It lowers blood glucose by increasing glucose absorption from the gut
B.
It raises blood glucose by stimulating glycogen breakdown in liver cells
C.
It lowers blood glucose by increasing uptake and storage of glucose
D.
It raises blood glucose by preventing cell respiration in muscles
Question 5
Which pancreatic endocrine cells secrete glucagon when blood glucose concentration falls?
A.
Beta cells
B.
Liver cells
C.
Alpha cells
D.
Adipose cells
Question 6
Which statement distinguishes osmoregulation from excretion?
A.
Osmoregulation increases body temperature; excretion decreases body temperature
B.
Osmoregulation controls solute concentration of body fluids; excretion removes metabolic wastes
C.
Osmoregulation removes urea; excretion controls blood glucose concentration
D.
Osmoregulation occurs only in the liver; excretion occurs only in endocrine glands
Question 7
Which nitrogenous waste is mainly excreted by mammalian kidneys after excess amino acids are broken down?
A.
Thyroxin
B.
Insulin
C.
Urea
D.
Glycogen
Question 8
Define homeostasis.
[1]
State one homeostatic variable in humans.
[1]
Question 9
What physiological change is most characteristic of type 2 diabetes in its early stages?
A.
The kidneys produce too much insulin in response to glucose
B.
Target cells respond weakly to insulin
C.
Pancreatic beta cells are destroyed by an autoimmune response
D.
Alpha cells stop secreting glucagon after meals
Question 10
What is the role of the hypothalamus in thermoregulation?
A.
It integrates temperature information and coordinates corrective responses
B.
It secretes sweat directly onto the surface of the skin
C.
It stores glycogen and releases glucose into the blood
D.
It filters blood plasma to remove urea and excess salts
Question 11
Why is sweating less effective at cooling the body in very humid air?
A.
Vasoconstriction increases blood flow through skin capillaries
B.
Brown adipose tissue produces less ATP in humid air
C.
Sweat glands secrete no water in humid air
D.
Evaporation of sweat from the skin is reduced
Question 12
Which feature helps maintain high hydrostatic pressure in the glomerulus?
A.
The proximal convoluted tubule contains many microvilli
B.
The efferent arteriole is narrower than the afferent arteriole
C.
The collecting duct passes through the medulla
D.
The descending limb is permeable to water
Question 13
What adaptation of cells in the proximal convoluted tubule increases the surface area for selective reabsorption?
A.
Contractile fibres in the lumen
B.
Podocyte slit gaps around capillaries
C.
Thick myelin sheaths around axons
D.
Microvilli on the apical membrane
Question 14
What is the role of active transport in the ascending limb of the loop of Henle?
A.
To move urea from the bladder into the blood
B.
To move glucose into urine after meals
C.
To move water into the filtrate and dilute the medulla
D.
To move sodium ions into the medulla and maintain a high osmotic concentration
Question 15
What urine would be produced when ADH secretion is very low?
A.
Urine containing red blood cells and plasma proteins
B.
A large volume of dilute urine
C.
A small volume of concentrated urine
D.
Urine containing all filtered glucose
Question 16
The diagram shows a generalized homeostatic feedback loop.
State the function of a receptor in the loop.
[1]
Outline why negative feedback is used rather than positive feedback in homeostasis.
[1]
Question 17
After a carbohydrate-rich meal, blood glucose concentration rises.
State the pancreatic endocrine cells that respond by secreting insulin.
[1]
Explain two effects of insulin on target tissues that lower blood glucose concentration.
[1]
Question 18
Distinguish between the physiological basis of type 1 diabetes and type 2 diabetes.
[1]
State two methods used to prevent or manage type 2 diabetes.
[1]
Question 19
State the role of peripheral thermoreceptors in thermoregulation.
[1]
Outline how the hypothalamus and pituitary gland can increase metabolic heat production.
[1]
Question 20
Explain how sweating cools the body.
[1]
State one behavioural response that can reduce overheating in mammals.
[1]
Question 21
Define osmoregulation.
[1]
Distinguish osmoregulation from excretion.
[1]
Question 22
A person drinks a large volume of water in a short time.
Predict the change in ADH secretion.
[1]
Explain the effect on aquaporin location.
[1]
Predict the effect on urine volume and concentration.
[1]
Question 23
Volunteers exercised for the same time in hot dry air and hot humid air. Sweat production and change in core temperature were recorded.
| Condition | Sweat production / dm³ h⁻¹ | Core temperature change / °C |
|---|---|---|
| Hot dry air | 1.1 | +0.6 |
| Hot humid air | 1.2 | +1.4 |
Compare sweat production in the two conditions.
[1]
State which condition caused the greater rise in core temperature.
[1]
Suggest why sweating did not cool the body as effectively in that condition.
[1]
Question 24
A simulation models a homeostatic variable after it is displaced above the set point. Two possible feedback responses are shown.
Identify which response shows negative feedback.
[1]
Describe the evidence from the graph for your answer.
[1]
Explain why the other response would be unsuitable for homeostasis.
[1]
Question 25
Blood osmotic concentration rises after prolonged sweating without water intake. What response is expected in the collecting ducts?
A.
The glomerular filtration barrier becomes permeable to plasma proteins
B.
More aquaporins are inserted into cell surface membranes
C.
Sodium transport in the ascending limb stops completely
D.
Aquaporins are removed from membranes into vesicles
Question 26
During vigorous physical activity, which change in blood supply is most likely?
A.
Increased blood flow to skeletal muscles and reduced blood flow to the gut
B.
Reduced blood flow to skeletal muscles and increased blood flow to the gut
C.
Complete loss of blood supply to the brain to supply muscles
D.
No change in any organ because cardiac output is fixed
Question 27
A glucose tolerance test is carried out on two people after they drink the same glucose solution.
State the expected shape of the blood glucose curve in a person without diabetes.
[1]
Explain why a person with diabetes may have a higher and more prolonged rise in blood glucose.
[1]
Question 28
Humans respond to cold conditions by vasoconstriction and shivering.
Explain how vasoconstriction reduces heat loss from the skin.
[1]
Explain how shivering increases heat production.
[1]
Question 29
The diagram shows part of a nephron and its blood supply.
State where ultrafiltration occurs.
[1]
Explain how the filtration barrier prevents most plasma proteins entering the filtrate.
[1]
State one small solute that normally enters Bowman’s capsule.
[1]
Question 30
State the main site of selective reabsorption of glucose in the nephron.
[1]
Explain how cells at this site are adapted for selective reabsorption.
[1]
Question 31
Explain how the ascending limb of the loop of Henle helps conserve water. [3]
Question 32
Blood osmotic concentration increases after water loss.
State the receptor and endocrine organ involved in the ADH response.
[1]
Explain how ADH changes water reabsorption in the collecting duct.
[1]
Question 33
During vigorous physical activity, blood supply to skeletal muscle changes.
State the change in arteriole diameter in active skeletal muscle.
[1]
Explain two benefits of increased blood flow to active skeletal muscle.
[1]
State one organ that may receive reduced blood flow during vigorous activity.
[1]
Question 34
Renal blood flow in an adult is 1200 cm³ min⁻¹ during wakeful rest and 900 cm³ min⁻¹ during sleep.
Calculate the percentage change in renal blood flow during sleep compared with wakeful rest.
[1]
Suggest one advantage of this change during sleep.
[1]
Question 35
A glucose tolerance test was carried out on two adults after they drank the same glucose solution.
Identify the adult whose results are more consistent with diabetes.
[1]
Describe two differences between the two blood glucose curves.
[1]
Explain why the curve for the adult with diabetes does not return rapidly to the starting concentration.
[1]
Question 36
A study compared lifestyle factors in adults with and without type 2 diabetes.
| Lifestyle factor | Category | Adults with type 2 diabetes / % |
|---|---|---|
| Body mass | Healthy weight | 5 |
| Body mass | Overweight | 11 |
| Body mass | Obese | 24 |
| Physical activity | High | 6 |
| Physical activity | Moderate | 10 |
| Physical activity | Low | 18 |
| High-sugar food intake | Low | 7 |
| High-sugar food intake | Moderate | 12 |
| High-sugar food intake | High | 20 |
Identify the lifestyle factor most strongly associated with type 2 diabetes in the data.
[1]
Describe one trend linking physical activity and type 2 diabetes frequency.
[1]
Suggest two prevention methods supported by the data.
[1]
Evaluate one limitation of using these data to infer causation.
[1]
Question 37
Thermal images of a hand were taken before and after exposure to cold air. Skin temperature and blood flow in finger capillaries were measured.
| Condition | Skin temperature / °C | Capillary blood flow / perfusion units |
|---|---|---|
| Before cold exposure | 33.7 | 46 |
| After cold exposure | 24.9 | 12 |
Describe the change in skin temperature after cold exposure.
[1]
Describe the change in capillary blood flow after cold exposure.
[1]
Explain how the change in blood flow helps maintain core temperature.
[1]
State one other physiological response to cold.
[1]
Question 38
The concentrations of selected substances were measured in blood plasma, glomerular filtrate and fluid leaving the proximal convoluted tubule.
| Substance | Plasma / % | Filtrate / % | Leaving PCT / % |
|---|---|---|---|
| Water | 100 | 100 | 100 |
| Ions | 100 | 100 | 98 |
| Glucose | 100 | 100 | 2 |
| Urea | 100 | 100 | 140 |
| Plasma proteins | 100 | 0.5 | 0 |
| Blood cells | 100 | 0 | 0 |
Identify one substance that is freely filtered at the glomerulus.
[1]
Identify one substance that is largely retained in the blood during ultrafiltration.
[1]
Explain the change in glucose concentration between glomerular filtrate and fluid leaving the proximal convoluted tubule.
[1]
Suggest why urea remains in the filtrate.
[1]
Question 39
Participants were given either water or a concentrated salt solution. Plasma osmotic concentration, ADH concentration and urine volume were measured over time.
| Time / min | Treatment | Plasma osmotic concentration / mOsm kg⁻¹ | ADH / pg mL⁻¹ | Urine volume / mL h⁻¹ |
|---|---|---|---|---|
| 0 | Water | 290 | 2.1 | 82 |
| 30 | Water | 287 | 1.4 | 110 |
| 60 | Water | 284 | 0.8 | 185 |
| 120 | Water | 286 | 0.9 | 245 |
| 180 | Water | 289 | 1.6 | 160 |
| 0 | Salt solution | 290 | 2.0 | 80 |
| 30 | Salt solution | 296 | 4.1 | 68 |
| 60 | Salt solution | 301 | 7.3 | 48 |
| 120 | Salt solution | 303 | 8.5 | 32 |
| 180 | Salt solution | 299 | 5.6 | 42 |
Identify the treatment that caused the greatest increase in ADH concentration.
[1]
Describe the relationship between ADH concentration and urine volume.
[1]
Explain the effect of ADH on collecting duct cells.
[1]
Question 40
Blood flow to four organs was measured during wakeful rest and vigorous exercise.
| Organ | Wakeful rest / cm³ min⁻¹ | Vigorous exercise / cm³ min⁻¹ |
|---|---|---|
| Skeletal muscle | 1200 | 12500 |
| Gut | 1400 | 600 |
| Brain | 750 | 800 |
| Kidneys | 1100 | 500 |
Identify the organ with the greatest percentage increase in blood flow during exercise.
[1]
Calculate the percentage change in blood flow to the gut during exercise compared with rest.
[1]
Explain why blood flow to skeletal muscle changes during exercise.
[1]
Question 41
Osmotic concentration was measured in filtrate at different regions of the loop of Henle and in the surrounding medulla.
Identify the region where sodium ions are actively transported out of the filtrate.
[1]
Describe the change in osmotic concentration of the medulla with depth.
[1]
Explain how active transport in the ascending limb produces the pattern shown.
[1]
Predict the effect on urine concentration if active transport of sodium ions in the ascending limb was inhibited.
[1]
Question 42
A trial tested a drug that blocks ADH receptors on collecting duct cells. Urine volume and urine osmotic concentration were measured before and after the drug was taken.
| Condition | Urine volume / dm3 day^-1 | Urine osmotic concentration / mOsm kg^-1 |
|---|---|---|
| Before drug | 1.6 | 820 |
| After drug | 4.7 | 260 |
Describe the effect of the drug on urine volume.
[1]
Describe the effect of the drug on urine osmotic concentration.
[1]
Explain these effects using the role of aquaporins.
[1]
Suggest one risk to a patient taking this drug without increasing water intake.
[1]
Question 43
Outline the components of a negative feedback loop in homeostasis.
[1]
Explain how negative feedback maintains a homeostatic variable within preset limits, including responses to values above and below the set point.
[1]
Question 44
State the pancreatic cell types that secrete insulin and glucagon.
[1]
Compare and contrast the regulation of blood glucose by insulin and glucagon.
[1]
Question 45
Distinguish the physiological changes that cause type 1 diabetes and type 2 diabetes.
[1]
Discuss prevention and treatment of diabetes, referring to differences between type 1 and type 2 diabetes.
[1]
Question 46
Outline the role of receptors and the hypothalamus in thermoregulation.
[1]
Explain physiological mechanisms used by humans to respond to overheating and cooling.
[1]
Question 47
Distinguish between osmoregulation and excretion in the kidney.
[1]
Explain how the glomerulus, Bowman’s capsule and proximal convoluted tubule contribute to excretion.
[1]
Question 48
Outline how the loop of Henle maintains a high osmotic concentration in the medulla.
[1]
Explain how ADH regulates water reabsorption in the collecting ducts.
[1]
Question 49
Describe how arteriole diameter changes blood supply to an organ.
[1]
Evaluate the pattern of blood supply to skeletal muscles, gut, brain and kidneys during vigorous activity compared with wakeful rest and sleep.
[1]
Question 50
State the role of aquaporins and the units used for osmotic concentration.
[1]
Discuss why both the loop of Henle and ADH are required for effective osmoregulation by the kidney.
[1]
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