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Questions and Answers
What is the role of the heat loss center located in the anterior hypothalamus?
What is the role of the heat loss center located in the anterior hypothalamus?
Shivering is a mechanism that decreases heat production in the body.
Shivering is a mechanism that decreases heat production in the body.
False
What causes the resetting of the hypothalamic thermostat during fever?
What causes the resetting of the hypothalamic thermostat during fever?
Release of prostaglandins from the hypothalamus
In response to cold weather, the body primarily ________ heat production through shivering.
In response to cold weather, the body primarily ________ heat production through shivering.
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Match the following mechanisms with their respective temperatures:
Match the following mechanisms with their respective temperatures:
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Which of the following is NOT a consequence of hot weather on the thermoregulatory system?
Which of the following is NOT a consequence of hot weather on the thermoregulatory system?
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Alcohol consumption inhibits shivering as a heat production mechanism.
Alcohol consumption inhibits shivering as a heat production mechanism.
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What is the definition of Basal Metabolic Rate (BMR)?
What is the definition of Basal Metabolic Rate (BMR)?
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Name one benefit of fever.
Name one benefit of fever.
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The normal body temperature range is 36.5 – 37.2 ºC.
The normal body temperature range is 36.5 – 37.2 ºC.
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What factor decreases BMR in individuals?
What factor decreases BMR in individuals?
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Normal body temperature is typically measured in degrees _____ and ranges from 36.6 to 37.2.
Normal body temperature is typically measured in degrees _____ and ranges from 36.6 to 37.2.
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Match the following basal metabolic rate values with the corresponding age group:
Match the following basal metabolic rate values with the corresponding age group:
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What is one effect of hyperthyroidism on BMR?
What is one effect of hyperthyroidism on BMR?
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People living in hot zones typically have an increased BMR.
People living in hot zones typically have an increased BMR.
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Which hormone is known to influence BMR?
Which hormone is known to influence BMR?
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Study Notes
Basal Metabolic Rate (BMR)
- Definition: The rate of heat loss in the body per unit time under specific conditions.
- It reflects the activity of vital organs (heart, lungs, liver, brain, nervous system, kidneys).
- Basal conditions:
- Complete mental, physical, and emotional rest.
- Post-absorptive state (12-14 hours after the last meal).
- Comfortable external temperature (neither shivering nor sweating).
Normal Values of Basal Metabolic Rate
- Newborn infant: 25 C/m²/hour
- 2-5 years: 60 C/m²/hour
- Adult male (20 years): 40 C/m²/hour
- Adult female (20 years): 36 C/m²/hour
- Every 10 years: BMR decreases by 1 C/m²/hour
Factors Affecting BMR
Factors Increasing BMR
- Male
- Athletes
- People living in cold zones
- High protein diet
- Pregnancy and lactation
- Stress
- Hyperthyroidism
- Hyperfunction of the adrenal cortex
- Hyperfunction of the adrenal medulla
- Fever
- Diabetes insipidus
- Heart failure
- Blood diseases (e.g., anemia)
Factors Decreasing BMR
- Female
- Sedentary people
- People living in hot zones
- Sleep
- Dark-colored people
- Hypothyroidism
- Hypofunction of the adrenal cortex
- Hypothermia
- Undernutrition and starvation
- Shock
Body Temperature
- Normal range: 36.6-37.2°C
Heat Balance
- The balance between heat production and heat loss determines body temperature.
- Normally, the rate of heat production equals the rate of heat loss.
- Temperature homeostasis is the balance in heat gain and heat loss.
Heat Gain
- Basal metabolic rate (BMR)
- Skeletal muscular activity
- Food intake
- Hormones (e.g., thyroid hormone)
- External environment (especially sun radiation)
Heat Loss
- Skin (85%, mainly through radiation)
- Respiratory tract (14%)
- Body excreta (1%)
Thermoregulatory System
- Thermoreceptors:
- Central thermo-receptors: located in the hypothalamus.
- Peripheral thermo-receptors: located in the skin.
- Temperature-regulating center (hypothalamic thermostat):
- Heat loss center: anterior hypothalamus.
- Heat gain center: posterior hypothalamus.
On Exposure to Hot Weather
- Body temperature tends to increase.
- A) Increase heat loss by:
- Vasodilation of cutaneous blood vessels.
- Sweating.
- B) Decrease heat production by:
- Inhibition of muscle tone.
- Loss of appetite (anorexia).
- Inhibition of thermogenic hormones (catecholamines and thyroid).
On Exposure to Cold Weather
- Body temperature tends to decrease.
- A) Increased heat production by:
- Shivering (rapid increase in heat production).
- Increased secretion of catecholamines and thyroid hormones.
- Increased sensation of hunger and appetite.
- B) Decrease heat loss by:
- Vasoconstriction of cutaneous vessels.
- Curling up in a ball (smaller surface area exposed to the environment).
- Wearing clothes (insulation).
Fever (Pyrexia)
- Definition: Elevation of body temperature due to resetting of the hypothalamic thermostat.
- Causes:
- Infection
- Physical trauma
- Stress
Pathophysiology of Fever
- Infection → release of interleukin-1 (IL-1) from macrophages → synthesis and release of prostaglandins (PGs) in the hypothalamus → reset thermostat at a new, higher level → fever.
- Aspirin inhibits PG production → decreasing fever.
Stages of Fever
- Stage 1 (chill): Resetting of the hypothalamus, decreased heat loss, increased heat production (shivering), pale skin, cold feeling.
- Stage 2 (steady state): Body temperature reaches the new set point, warmth, flushed skin, shivering stops.
- Stage 3 (defervescence): Removal of the causative factor, set point returns to normal, hypothalamic thermostat decrease temperature (cutaneous vasodilation and sweating).
Benefits of Fever
- Increase production of antibodies.
- Prevent growth of certain microorganisms.
- Prevent the growth of certain tumors.
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Description
Explore the essential concepts of Basal Metabolic Rate (BMR) including its definition, normal values across different ages, and the various factors that can affect it. This quiz provides a comprehensive look at how BMR functions, its significance in physiology, and the impact of lifestyle on metabolic rates.
