Unit 11 — Metabolism & Body Temperature · Question Bank

TMU Physiology · Metabolism & Body Temperature · Guyton 14e Ch 72–74
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Q1
The main storage form of body energy is:
TMU 题-Metabolism
A. fat
B. hepatic glycogen
C. muscle glycogen
D. protein
✅ Answer: A. fat
Fat is the body's main long-term energy store (energy-dense, ~9.3 kcal/g); glycogen stores are small.
Q2
The respiratory quotient (RQ) of a mixed diet is about:
TMU 题-Metabolism
A. 0.70
B. 0.85
C. 0.80
D. 1.00
✅ Answer: B. 0.85
Mixed food RQ ≈ 0.85. Carbohydrate = 1.0, fat = 0.70, protein = 0.80.
Q3
Which is the WRONG condition for measuring the basal metabolic rate?
TMU 题-Metabolism
A. after a night of restful sleep
B. 12–14 hours after the last meal
C. no physical activity, standing still
D. quiet surroundings at normal room temperature
✅ Answer: C. no physical activity, standing still
BMR is measured LYING DOWN, awake, physically and mentally at rest — not standing.
Q4
If body temperature rises above the set point, the responses are to:
TMU 题-Metabolism
A. increase heat production
B. decrease heat loss
C. decrease heat loss and increase heat production
D. increase heat loss and decrease heat production
✅ Answer: D. increase heat loss and decrease heat production
Too hot → skin vasodilation and sweating (↑heat loss) plus ↓heat production — negative feedback to lower temperature.
Q5
If body temperature falls below the set point, the responses are to:
TMU 题-Metabolism
A. decrease heat loss and increase heat production
B. decrease heat loss only
C. increase heat production only
D. increase heat loss and decrease heat production
✅ Answer: A. decrease heat loss and increase heat production
Too cold → vasoconstriction and piloerection (↓heat loss) plus shivering (↑heat production).
Q6
In a warm environment, the main route of body heat loss is:
TMU 题-Metabolism
A. radiation
B. evaporation
C. conduction
D. convection
✅ Answer: B. evaporation
When ambient temperature approaches or exceeds skin temperature, radiation/conduction/convection fail, so evaporation (sweating) becomes the only effective route.
Q7
The main way to increase heat production in a cold environment is:
TMU 题-Metabolism
A. food specific dynamic action
B. increased liver metabolism
C. shivering of skeletal muscle
D. increased metabolism of all viscera
✅ Answer: C. shivering of skeletal muscle
Shivering thermogenesis in skeletal muscle is the chief acute mechanism for raising heat production in the cold.
Q8
Which nutrient has the highest specific dynamic action (greatest post-meal heat production)?
TMU 题-Metabolism
A. glucose
B. fat
C. they are equal
D. protein
✅ Answer: D. protein
Protein has the highest specific dynamic action (~30%), much more than carbohydrate or fat.
Q9
The thermoregulatory centre that responds directly to temperature is located in the:
TMU 题-Metabolism
A. preoptic area of the hypothalamus
B. medulla oblongata
C. cerebral cortex
D. spinal cord
✅ Answer: A. preoptic area of the hypothalamus
The preoptic/anterior hypothalamus contains temperature-sensitive neurons that compare blood temperature with the set point.
Q10
Which measurement best represents the body's core temperature?
TMU 题-Metabolism
A. axillary temperature
B. skin temperature
C. rectal temperature
D. finger temperature
✅ Answer: C. rectal temperature
Rectal temperature (~37.1–37.5 °C) is closest to the deep core temperature; axillary/skin readings are lower and variable (shell).
Q11
Metabolic rate is defined as the:
TMU 题-Metabolism
A. amount of food eaten per day
B. oxygen stored in the body
C. amount of energy liberated per unit time
D. heat lost by evaporation
✅ Answer: C. amount of energy liberated per unit time
Metabolic rate = energy liberated per unit time (often expressed as heat or O₂ consumption).
Q12
The respiratory quotient is defined as:
TMU 题-Metabolism
A. O₂ consumed ÷ CO₂ produced
B. CO₂ produced × O₂ consumed
C. energy ÷ time
D. CO₂ produced ÷ O₂ consumed
✅ Answer: D. CO₂ produced ÷ O₂ consumed
RQ = volume of CO₂ produced / volume of O₂ consumed during metabolism of a foodstuff.
Q13
The approximate caloric value of fat is:
Guyton 14e
A. 9.3 kcal/g
B. 4.1 kcal/g
C. 1.0 kcal/g
D. 5.0 kcal/g
✅ Answer: A. 9.3 kcal/g
Fat yields ~9.3 kcal/g — more than twice carbohydrate or protein (~4.1 kcal/g each), making it the densest energy store.
Q14
The single most important hormone setting the basal metabolic rate is:
Guyton 14e
A. insulin
B. thyroid hormone
C. cortisol
D. parathyroid hormone
✅ Answer: B. thyroid hormone
Thyroid hormone is the chief hormonal determinant of BMR (calorigenic); adrenaline and fever also raise it (~13% per °C).
Q15
At rest, the organ that produces the most body heat is the:
Guyton 14e
A. skeletal muscle
B. skin
C. liver (and other viscera)
D. brain
✅ Answer: C. liver (and other viscera)
At rest the liver/viscera generate most heat; during exercise or shivering, skeletal muscle dominates heat production.
Q16
Heat loss by emission of infrared rays to cooler surroundings is called:
Guyton 14e
A. conduction
B. convection
C. evaporation
D. radiation
✅ Answer: D. radiation
Radiation (infrared emission) is the main route of heat loss at rest in a cool room. Conduction = direct contact; convection = moving air; evaporation = sweat.
Q17
During the onset (chill phase) of a fever, the patient:
TMU 题-Metabolism
A. shivers and vasoconstricts as temperature rises to the new set point
B. sweats and vasodilates
C. loses consciousness
D. has a falling temperature
✅ Answer: A. shivers and vasoconstricts as temperature rises to the new set point
Pyrogens raise the set point, so the body feels cold → shivering + vasoconstriction generate and conserve heat until temperature reaches the new set point.
Q18
Core temperature is held nearly constant at about:
Guyton 14e
A. 35 °C
B. 37 °C
C. 39 °C
D. 40 °C
✅ Answer: B. 37 °C
Core (deep) temperature is regulated around ~37 °C; the shell (skin/limbs) varies with the environment.
Q19
The carbohydrate respiratory quotient is:
TMU 题-Metabolism
A. 0.70
B. 0.80
C. 1.00
D. 0.85
✅ Answer: C. 1.00
Pure carbohydrate metabolism gives RQ = 1.00; fat = 0.70 (more O₂ needed per CO₂).
Q20
Fever resolves (defervescence/crisis) when the set point falls back to normal, causing:
TMU 题-Metabolism
A. shivering
B. vasoconstriction
C. piloerection
D. sweating and vasodilation to lose heat
✅ Answer: D. sweating and vasodilation to lose heat
Once the set point resets, the actual temperature is now ABOVE it, so the body sweats and vasodilates to bring the temperature down.
1Energy metabolism+
The release, storage, transfer and utilisation of energy that accompanies the chemical reactions of metabolism in the body — measured as metabolic rate (energy liberated per unit time).
TMU 题-Metabolism
2Respiratory quotient (RQ)+
The ratio of CO₂ produced to O₂ consumed during the metabolism of a foodstuff: carbohydrate 1.00, protein 0.80, fat 0.70, mixed diet ~0.85. It indicates which fuel is being oxidised.
TMU 题-Metabolism
3Basal metabolic rate (BMR)+
The metabolic rate measured under standard basal conditions — awake but physically and mentally at rest, lying down, 12–14 h after a meal (post-absorptive), in a thermoneutral, quiet environment. It is the minimum energy to sustain life and is chiefly set by thyroid hormone.
TMU 题-Metabolism
4Specific dynamic action (SDA)+
The extra heat produced by the body in processing ingested food. It is highest for protein (~30%) and much lower for carbohydrate and fat — which is why BMR is measured in the post-absorptive state.
TMU Metabolism slide
5Core temperature+
The temperature of the deep tissues (brain, thorax, abdomen), held nearly constant at ~37 °C and best represented clinically by the rectal temperature. The shell temperature (skin/limbs) varies with the environment.
TMU 题-Metabolism
6Set point+
The reference temperature (~37 °C) against which the hypothalamic thermoregulatory centre compares actual body temperature, driving heat-loss or heat-gain responses by negative feedback. Pyrogens raise the set point to produce fever.
TMU 题-Metabolism
Essay 1
Explain fever using the set-point theory of thermoregulation.
10 marks

Normal control

The hypothalamic thermoregulatory centre (preoptic area) defends a set point of ~37 °C by negative feedback.

Raising the set point

Pyrogens (from infection/inflammation), acting via prostaglandin E₂, RAISE the hypothalamic set point above 37 °C.

Onset (chill phase)

The actual temperature is now BELOW the new set point, so the body behaves as if cold: vasoconstriction + shivering generate and conserve heat → the temperature climbs to the new (higher) set point. The patient feels cold despite a rising fever.

Plateau

Temperature is held at the elevated set point.

Defervescence (crisis)

When the set point falls back to normal (recovery or antipyretic), the temperature is now ABOVE it → vasodilation + sweating → the temperature falls.

Marking guide (10 marks): normal set point control 1.5 · pyrogens/PGE₂ raise set point 2.5 · chill phase (shiver/vasoconstrict to rise) 3 · plateau 1 · crisis (sweat/vasodilate to fall) 2
Essay 2
Define the basal metabolic rate and describe the conditions and factors that affect it.
10 marks

Definition

The BMR is the metabolic rate (energy expenditure per unit time) measured under standard basal conditions — the minimum energy needed to keep the body alive at rest.

Basal conditions

  • Awake but physically and mentally at rest, lying down (not standing).
  • Post-absorptive — 12–14 h after the last meal (no specific dynamic action).
  • Thermoneutral environment (~20–25 °C, quiet).
  • Normal body temperature.

Factors raising BMR

Thyroid hormone (the main determinant), fever (~13% per °C), adrenaline; higher in males, children and in cold climates. It falls with age and in hypothyroidism/starvation.

Marking guide (10 marks): definition 2 · awake/rest/lying 1.5 · post-absorptive 1.5 · thermoneutral 1 · normal temperature 1 · factors (thyroid main, fever, age, sex) 3
Essay 3
Describe energy metabolism, including caloric values and the respiratory quotient.
10 marks

Energy sources and storage

Immediate fuel is glucose/ATP; the main long-term store is fat (energy-dense). Caloric values: carbohydrate and protein ~4.1 kcal/g, fat ~9.3 kcal/g.

Respiratory quotient

RQ = CO₂ produced ÷ O₂ consumed. Carbohydrate = 1.00, protein = 0.80, fat = 0.70, mixed diet ≈ 0.85. The RQ reveals which fuel is being oxidised (a low RQ indicates fat oxidation, e.g. in fasting).

Specific dynamic action

The extra heat produced after eating, highest for protein (~30%) — which is why the post-absorptive state is required for BMR.

Marking guide (10 marks): energy sources + fat as main store 2 · caloric values (4.1 / 9.3) 2 · RQ definition + values 3 · low RQ = fat oxidation 1 · specific dynamic action 2
Essay 4
Describe the routes of heat production and heat loss in the body.
10 marks

Heat production

  • At rest: the liver and other viscera are the main source.
  • In cold / during activity: skeletal-muscle shivering is the chief way to raise heat production.
  • Also: hormones (thyroxine, adrenaline → non-shivering thermogenesis) and the specific dynamic action of food.

Heat loss

  • Radiation — infrared emission; main route at rest in a cool room.
  • Conduction — to cooler objects in contact.
  • Convection — heat carried away by moving air/water.
  • Evaporation (sweat) — uses the latent heat of vaporisation; the ONLY effective route when ambient temperature ≥ skin temperature.
Marking guide (10 marks): production — liver at rest 1.5, shivering in cold 2, hormones/SDA 1.5 · loss — radiation 1.5, conduction 1, convection 1, evaporation (only route when hot) 1.5
Essay 5
Describe how the body regulates its temperature when it deviates from the set point.
10 marks

The controller

The thermoregulatory centre in the preoptic area of the hypothalamus compares blood temperature with a set point (~37 °C) and drives negative-feedback responses.

If body temperature is ABOVE the set point (too hot)

  • Increase heat loss: cutaneous vasodilation and sweating (evaporation).
  • Decrease heat production.

If body temperature is BELOW the set point (too cold)

  • Decrease heat loss: cutaneous vasoconstriction and piloerection.
  • Increase heat production: shivering (and hormonal/non-shivering thermogenesis).

Result

These opposing responses return the core temperature toward the set point, keeping it nearly constant.

Marking guide (10 marks): hypothalamic centre + set point + negative feedback 3 · too hot → ↑heat loss (vasodilation/sweat) + ↓production 3 · too cold → ↓heat loss (vasoconstriction) + ↑production (shivering) 3 · return to set point 1