Age-Related Changes in Thermoregulation — MCQs
A patient presents with a temperature of 40°C and flushed skin. Which of the following interventions is most appropriate to lower the body temperature?
Thermoregulatory response activated by cold is:
A person working in a hot environment who consumes more water without salt is likely to develop a condition called
Which of the following is NOT true about heat stroke?
A 72-year-old man undergoes resection of an abdominal aneurysm. He arrives in the ICU with a core temperature of 33°C (91.4°F) and shivering. Which of the following is a physiologic consequence of the shivering?
Which of the following measurement sites most closely reflects core body temperature?
In human beings, the least useful physiological response to low environmental temperature is:
A cold exposure which is expected to bring the body temperature from 37°C to 20°C, actually brings it down to only 36.5°C. Calculate the 'Gain' of the thermoregulatory system.
Lesion of preoptic nucleus of hypothalamus is associated with which of the following conditions?
All of the following regarding ankylosing spondylitis are true except:
Age-Related Changes in Thermoregulation Indian Medical PG Practice Questions and MCQs
Question 1: A patient presents with a temperature of 40°C and flushed skin. Which of the following interventions is most appropriate to lower the body temperature?
- A. Applying a heating blanket
- B. Increasing room temperature
- C. Providing warm fluids
- D. Administering antipyretics (Correct Answer)
Explanation: ***Administering antipyretics*** - **Antipyretics** such as acetaminophen or ibuprofen directly act on the **hypothalamus** to reset the body's thermoregulatory set point, promoting heat loss and reducing fever [1]. - They are the most appropriate first-line intervention for **febrile patients** with a high temperature, as they address the underlying mechanism of fever [3]. *Applying a heating blanket* - This intervention would **increase** the patient's body temperature, which is the opposite of the desired effect for a patient with a fever of 40°C. - **Heating blankets** are used for hypothermia, not hyperthermia. *Increasing room temperature* - Raising the room temperature would make it harder for the patient's body to dissipate heat, potentially leading to a **further increase** in body temperature [1]. - A cooler environment promotes heat loss through **convection** and **radiation** [1], [4]. *Providing warm fluids* - While hydration is important, providing **warm fluids** would add heat to the patient's body, which is counterproductive in this situation [2]. - **Cool or room-temperature fluids** are generally preferred for hydration during fever to avoid contributing to the elevated body temperature [2].
Question 2: Thermoregulatory response activated by cold is:
- A. Increased respiration
- B. Cutaneous vasodilatation
- C. Increased voluntary activity (Correct Answer)
- D. Anorexia
Explanation: ***Increased voluntary activity*** - Among the given options, **increased voluntary activity** is the correct answer as it represents a behavioral thermoregulatory response that generates heat through **muscle contraction** (e.g., moving around, exercising, stamping feet). - While the **primary physiological responses** to cold include **shivering** (involuntary muscle contraction), **vasoconstriction**, and **non-shivering thermogenesis** (brown fat), voluntary physical activity does contribute to heat production and is a recognized cold-adaptive behavior. - Voluntary activity increases metabolic rate and heat generation, helping maintain core body temperature in cold environments. *Increased respiration* - While respiration rate may increase slightly in cold due to metabolic changes, it is **not a primary thermoregulatory mechanism** for heat production. - The main purpose of respiration is **gas exchange**, not heat generation. - This is not a recognized thermoregulatory response to cold exposure. *Cutaneous vasodilatation* - **Cutaneous vasodilatation** (widening of skin blood vessels) leads to increased blood flow to the skin, which facilitates **heat loss** and is a response to **heat**, not cold. - In cold conditions, the body undergoes **cutaneous vasoconstriction** (narrowing of skin blood vessels) to minimize heat loss and preserve core temperature. - This option represents the **opposite** of what occurs in cold. *Anorexia* - **Anorexia** (loss of appetite) is not a thermoregulatory response to cold. - In fact, cold exposure typically **increases appetite and food intake** to support increased metabolic heat production. - Reduced food intake would impair the body's ability to generate heat through metabolism.
Question 3: A person working in a hot environment who consumes more water without salt is likely to develop a condition called
- A. Heat cramps (Correct Answer)
- B. Heat stroke
- C. Heat hyperpyrexia
- D. Heat exhaustion
Explanation: ***Heat cramps*** - This condition occurs due to **excessive sweating** in a hot environment, leading to significant **electrolyte (salt) loss**, particularly sodium. - Consuming large amounts of **plain water without electrolyte replacement** further dilutes the remaining electrolytes in the body, exacerbating hyponatremia and increasing the likelihood of painful muscle cramps. *Heat stroke* - **Heat stroke** is a life-threatening condition characterized by a **core body temperature >104°F (40°C)** and central nervous system dysfunction (e.g., altered mental status). - While fluid and electrolyte imbalances can contribute, its defining feature is the severe **thermoregulatory failure** leading to organ damage, which is distinct from simple muscle cramps. *Heat hyperpyrexia* - This term refers to an **extremely high body temperature** (often above 106°F or 41.1°C) but is not a specific diagnosis in the context of heat-related illness. - It is more of a symptom that could be present in severe heatstroke, not a primary condition resulting from excessive plain water intake. *Heat exhaustion* - **Heat exhaustion** presents with symptoms like fatigue, dizziness, nausea, and profuse sweating, but without significant central nervous system dysfunction or extremely high core body temperature. - While it involves fluid and electrolyte loss, the specific scenario of drinking plain water without salt primarily leads to muscle cramps due to electrolyte dilution, rather than the broader symptoms of heat exhaustion.
Question 4: Which of the following is NOT true about heat stroke?
- A. Sweating is absent
- B. Mental confusion occurs
- C. Body temperature >104°F
- D. Hypothermia occurs (Correct Answer)
Explanation: ***Hypothermia occurs*** - **Heat stroke** is characterized by a dangerous elevation of body temperature (**hyperthermia**), not a decrease, making hypothermia an incorrect statement about its presentation. - The core body temperature in heat stroke is typically **above 104°F (40°C)**, indicating severe overheating [1]. *Mental confusion occurs* - **Neurological dysfunction**, including disorientation, confusion, seizures, or coma, is a hallmark sign and a primary diagnostic criterion for heat stroke [1]. - This symptom reflects the impact of extreme heat on the central nervous system. *Sweating is absent* - In **classic (non-exertional) heat stroke**, the skin is often hot and dry because the thermoregulatory mechanism (sweating) has failed [1]. - However, in **exertional heat stroke**, sweating may still be present due to high metabolic activity, but it's ineffective at cooling the body [1], [2]. *Body temperature >104°F* - A **core body temperature equal to or exceeding 104°F (40°C)** is a critical diagnostic criterion for heat stroke [1]. - This excessively high temperature signifies the body's inability to regulate its heat.
Question 5: A 72-year-old man undergoes resection of an abdominal aneurysm. He arrives in the ICU with a core temperature of 33°C (91.4°F) and shivering. Which of the following is a physiologic consequence of the shivering?
- A. Rising mixed venous O2 saturation
- B. Rising base excess
- C. Increased production of CO2 (Correct Answer)
- D. Decreased consumption of O2
Explanation: ***Increased production of CO2*** - Shivering is a physiological response to **hypothermia** that involves rapid, involuntary muscle contractions. - This muscle activity significantly increases **metabolic rate**, leading to higher oxygen consumption and consequently, increased **carbon dioxide production**. *Rising mixed venous O2 saturation* - Shivering increases tissue oxygen demand, therefore, the peripheral tissues extract more oxygen from the blood. - This increased extraction would lead to a *decrease* in mixed venous O2 saturation, as less oxygen returns to the heart. *Rising base excess* - Increased metabolic activity from shivering can lead to the production of **lactic acid** if oxygen demand outstrips supply (anaerobic metabolism). - This would result in **metabolic acidosis**, which is characterized by a *negative* base excess (or decreasing base excess), not a rising one. *Decreased consumption of O2* - Shivering is an active process that requires energy, and this energy is primarily generated through **aerobic metabolism** in the muscles. - Therefore, shivering leads to a significant *increase* in oxygen consumption, not a decrease.
Question 6: Which of the following measurement sites most closely reflects core body temperature?
- A. Axillary
- B. Oral
- C. Surface
- D. Rectal (Correct Answer)
Explanation: ***Rectal*** - **Rectal temperature** is considered the most accurate non-invasive measure of **core body temperature** because of its proximity to the body's internal organs and consistent blood supply. - It is typically about **0.5-0.7°C higher than oral temperature** and reflects the true core warmth of the body. *Axillary* - **Axillary temperature** is taken in the armpit and is generally the **least accurate** and lowest reading. - It often **underestimates core body temperature** by 1°C or more due to exposure to ambient air. *Oral* - **Oral temperature** is a common and convenient site for temperature measurement but can be influenced by recent ingestion of hot or cold foods/liquids, or breathing through the mouth. - While generally reliable, it typically measures about **0.5°C lower than rectal temperature**. *Surface* - **Surface temperature**, such as that taken on the skin (e.g., forehead thermometer), is highly variable and easily affected by environmental factors like ambient temperature, airflow, and sweating. - It provides a less accurate reflection of the **body's internal core temperature** compared to deeper measurements.
Question 7: In human beings, the least useful physiological response to low environmental temperature is:
- A. Shivering
- B. Vasoconstriction
- C. Release of thyroxine
- D. Piloerection (Correct Answer)
Explanation: ***Piloerection*** - **Piloerection**, or 'goosebumps,' is a vestigial reflex in humans, meaning it has lost most of its original function. - While it causes hair to stand on end, which would trap an insulating layer of air in furry animals, humans lack sufficient body hair for this to be an **effective heat retention mechanism**. *Shivering* - **Shivering** involves involuntary muscle contractions that generate heat through increased metabolic activity. - This is a highly effective and significant physiological response for **acute heat production** in response to cold. *Vasoconstriction* - **Vasoconstriction** of peripheral blood vessels reduces blood flow to the skin, thereby decreasing heat loss to the environment through conduction, convection, and radiation. - This is a crucial mechanism for **conserving core body heat** in cold conditions. *Release of thyroxine* - The **release of thyroxine** (thyroid hormone) increases the body's basal metabolic rate over a longer term, leading to increased heat production. - This is an important **adaptive response to prolonged cold exposure**, rather than an immediate one.
Question 8: A cold exposure which is expected to bring the body temperature from 37°C to 20°C, actually brings it down to only 36.5°C. Calculate the 'Gain' of the thermoregulatory system.
- A. 33 (Correct Answer)
- B. 34
- C. 16.5
- D. 66
Explanation: ***33*** - The **error signal** (or uncorrected temperature drop) is the difference between the actual drop and the expected drop without regulation. Here, the expected drop is 37°C - 20°C = 17°C. The actual drop is 37°C - 36.5°C = 0.5°C. So, the error signal caused by the regulatory system's action is 36.5°C - 20°C = 16.5°C. Alternatively calculated as 17°C (expected) - 0.5°C (actual) = 16.5°C. - The **gain** of a thermoregulatory system is calculated as the expected change in temperature (without regulation) divided by the actual observed change in temperature after regulation when the body resists the change. Here, the body would have cooled by 17°C (37°C - 20°C) without compensation, but it only cooled by 0.5°C (37°C - 36.5°C). The gain is therefore 16.5 / 0.5 = 33. *34* - This answer likely arises from a miscalculation of the error signal or the expected temperature drop. - The key is to correctly identify the **change that would have occurred without regulation** and the **change that actually occurred.** *16.5* - This value represents the **change in temperature that was prevented by the thermoregulatory system** (17°C expected drop minus 0.5°C actual drop), but it is not the gain. - The gain is a ratio, not an absolute temperature difference. *66* - This value would result from an incorrect calculation, possibly by inverting the gain formula or multiplying by an incorrect factor. - The gain is specifically the ratio of the "corrected" change to the "uncorrected" error.
Question 9: Lesion of preoptic nucleus of hypothalamus is associated with which of the following conditions?
- A. Impaired thermoregulation
- B. Increased body temperature
- C. Hyperthermia (Correct Answer)
- D. Normal thermoregulation
Explanation: ***Hyperthermia*** - The **preoptic nucleus** of the anterior hypothalamus is the primary **heat-loss center** containing warm-sensitive neurons. - Lesion of this area impairs **heat dissipation mechanisms** (sweating, cutaneous vasodilation), preventing the body from lowering its temperature. - Results in **hyperthermia** - a pathological elevation of core body temperature due to failure of heat dissipation, not a change in set point. - This is the **most specific and clinically accurate** term for this condition. *Impaired thermoregulation* - While technically true, this is too **broad and non-specific**. - Impaired thermoregulation could refer to inability to either increase or decrease temperature. - In medical terminology, we use more specific terms like "hyperthermia" to describe the actual clinical condition. *Increased body temperature* - This is a **general descriptive term** rather than a specific clinical diagnosis. - While the body temperature is indeed increased, **hyperthermia** is the precise medical term that indicates the mechanism (impaired heat dissipation). - Less specific than "hyperthermia" for exam purposes. *Normal thermoregulation* - Clearly incorrect - a lesion in the primary thermoregulatory center would **abolish normal temperature control**. - The preoptic nucleus is essential for detecting and responding to temperature changes.
Question 10: All of the following regarding ankylosing spondylitis are true except:
- A. HLA B27 is positive in >90%
- B. More common in males than females
- C. Non-erosive arthritis (Correct Answer)
- D. Typically occurs in late teens to early adulthood (peak onset 20s-30s), but can present after 40 in rare cases
Explanation: ***Non-erosive arthritis*** - Ankylosing spondylitis is characterized by **erosive changes**, particularly at the discovertebral and sacroiliac joints, which can lead to **syndesmophyte formation** and eventual *ankylosis* (fusion) of the spine [1]. - The disease involves inflammation and subsequent **ossification of ligaments**, leading to structural damage rather than being purely non-erosive [1]. *HLA B27 is positive in >90%* - A strong association with **HLA-B27** is a hallmark of ankylosing spondylitis, with over 90% of Caucasian patients testing positive, making it a key diagnostic marker [1]. - While not universally present, its high prevalence further supports this statement as being true [1]. *More common in males than females* - Ankylosing spondylitis typically has a male-to-female predominance, with males generally experiencing **more severe disease progression** and spinal involvement. - While the diagnostic criteria have evolved to recognize a more equitable distribution, the classic presentation often highlights male prevalence. *Typically occurs in late teens to early adulthood (peak onset 20s-30s), but can present after 40 in rare cases* - The onset of ankylosing spondylitis symptoms most commonly occurs in **young adults**, typically between the ages of 20 and 40 [1]. - While less common, a small percentage of patients may experience symptom onset later in life, though this is less typical of the disease's natural history.
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