Body Temperature Regulation

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Questions and Answers

What is the primary mechanism of heat production in the body?

Metabolic activities (correct)

Muscular activity

Radiation of heat from the environment

Shivering

What is the role of thyroxin (T4) and adrenaline in heat production?

They decrease heat production by slowing down metabolic activities

They increase heat production by accelerating metabolic activities (correct)

They lead to heat loss from the body

They have no effect on heat production

What is the approximate percentage of heat lost from the body through conduction to air?

80%

15% (correct)

50%

What occurs when the environmental temperature is higher than the body temperature?

Heat is gained by the body Signup and view all the answers

What is the primary method of heat loss from the body?

Skin Signup and view all the answers

What is the term for the rapid involuntary contraction or twitching of muscles during exposure to cold?

Shivering Signup and view all the answers

How many calories of heat are produced during fat metabolism?

9 calories Signup and view all the answers

What percentage of heat is lost from the body by direct conduction from the surface of the body to solid objects?

3% Signup and view all the answers

What is the primary function of the skin in terms of temperature regulation?

To act as a controlled 'heat radiator' system Signup and view all the answers

What is the significance of the continuous venous plexus beneath the skin?

It supplies blood to the skin from the body core Signup and view all the answers

What happens to heat conductance between the core and the skin surface when the skin is fully vasodilated compared to fully vasoconstricted?

It increases eightfold Signup and view all the answers

What is the ratio of cold receptors to warmth receptors in the skin?

10:1 Signup and view all the answers

Where are deep body temperature receptors mainly found?

In the spinal cord, abdominal viscera, and great veins Signup and view all the answers

How do deep body temperature receptors function differently from skin receptors?

They are exposed to the body core temperature rather than the body surface temperature Signup and view all the answers

What is the primary role of temperature receptors in the hypothalamus?

To regulate body temperature Signup and view all the answers

What is the significance of blood flow to the skin from the body core?

It provides an effective mechanism for heat transfer from the body core to the skin Signup and view all the answers

What is the posterior hypothalamus also known as?

Heat gain center or heat production center Signup and view all the answers

What happens to skin blood vessels when body temperature increases?

Vasodilation occurs Signup and view all the answers

What is the effect of increasing sweat secretion on body temperature?

It helps to cool the body Signup and view all the answers

What is the role of the anterior hypothalamic preoptic area in thermoregulation?

It detects changes in body temperature Signup and view all the answers

What happens to shivering when body temperature increases?

It decreases Signup and view all the answers

What is the primary function of the heat loss center in the preoptic area?

To promote heat loss Signup and view all the answers

What happens to chemical thermogenesis when body temperature increases?

It decreases Signup and view all the answers

What is the overall function of the hypothalamic thermoregulatory center?

To maintain body temperature Signup and view all the answers

What is the average normal body temperature of a human when measured orally?

37°C (98.6°F) Signup and view all the answers

How does the body temperature of infants differ from that of adults immediately after birth?

It varies with environmental temperature due to an immature regulatory system. Signup and view all the answers

What effect does exercise have on body temperature?

It raises body temperature due to heat production in muscles. Signup and view all the answers

At what time of day is body temperature typically the lowest?

In the early morning Signup and view all the answers

What happens to body temperature during sleep?

It decreases by 0.5°C. Signup and view all the answers

How does a woman’s body temperature change during her menstrual cycle?

It rises sharply after ovulation and decreases during the menstrual phase. Signup and view all the answers

Which factor is most likely to lead to a rise in body temperature?

Emotional stress Signup and view all the answers

What is the effect of age on body temperature as one gets older?

Body temperature decreases slightly. Signup and view all the answers

What physiological response primarily prevents heat loss when body temperature decreases?

Skin vasoconstriction Signup and view all the answers

Which area of the brain is responsible for initiating shivering in response to low body temperature?

Posterior hypothalamus Signup and view all the answers

Which hormones are stimulated by the sympathetic centers to increase metabolic reactions during cold exposure?

Adrenaline and noradrenaline Signup and view all the answers

What is the result of chemical thermogenesis in the body when temperatures drop?

Increased rate of cellular metabolism Signup and view all the answers

What effect does thyrotropic releasing hormone (TRH) have in the heat production process?

Stimulates release of thyroid stimulating hormone (TSH) Signup and view all the answers

What is the primary mechanism through which shivering generates heat in the body?

Through severe muscular contractions Signup and view all the answers

What happens to the blood flow to the skin when body temperature drops?

Blood flow to the skin decreases Signup and view all the answers

What role does the anterior hypothalamus play when body temperature decreases?

Controls heat gain mechanisms Signup and view all the answers

Study Notes

Normal Body Temperature

Normal body temperature is around 37.8°C (100°F) and remains relatively constant, except when a person has a febrile illness.
The normal oral temperature is 37°C (98.6°F), which can vary between 35.8°C and 37.3°C (96.4°F and 99.1°F).
The skin temperature, on the other hand, rises and falls with the temperature of the surroundings.

Physiological Variations of Body Temperature

In infants, body temperature varies according to environmental temperature for the first few days after birth due to an underdeveloped temperature regulating system.
In children, body temperature is slightly higher (0.5°C) than in adults due to increased physical activity.
In old age, body temperature decreases slightly due to reduced heat production.
In females, body temperature is lower due to a lower basal metabolic rate compared to males.
Body temperature follows a diurnal variation, with a 1°C decrease in the early morning and a 1°C increase in the afternoon.
Body temperature also fluctuates after meals, exercise, sleep, emotional conditions, and during the menstrual cycle.

Heat Balance

Heat balance is crucial for maintaining a constant body temperature, which depends on the balance between heat produced in the body and heat lost from the body.
Heat production in the body occurs through metabolic activities, muscular activity, hormonal regulations (thyroxin and adrenaline), and radiation from the environment.
Heat loss from the body occurs through the skin (maximum heat loss), respiratory system, kidney, and gastrointestinal tract.

Mechanisms of Heat Gain and Loss

Conduction: A small amount of heat is lost from the body through direct contact with solid objects, while a larger proportion of heat is lost through conduction to air.
Insulation beneath the skin helps maintain a normal internal core temperature despite temperature fluctuations in the surroundings.
Blood flow to the skin from the body core provides an effective means of heat transfer.
The skin acts as a controlled "heat radiator" system, with blood flow regulating heat transfer from the body core to the skin.

Detection of Temperature

Temperature receptors in the skin and deep body tissues play a crucial role in temperature regulation.
The skin has more cold receptors than warmth receptors, making it more sensitive to detecting cool and cold temperatures.
Deep body temperature receptors are found in the spinal cord, abdominal viscera, and great veins in the upper abdomen and thorax.

Heat Gain Center and Heat Loss Center

The posterior hypothalamus acts as the heat gain center, stimulating heat production through shivering and metabolic reactions.
The preoptic area in the hypothalamus acts as the heat loss center, promoting heat loss through vasodilation and sweat secretion.

Mechanisms that Decrease or Increase Body Temperature

When the body temperature increases, the heat loss center in the preoptic area is stimulated, promoting heat loss through vasodilation and sweat secretion.
When the body temperature decreases, the heat gain center in the posterior hypothalamus is stimulated, promoting heat production through shivering and metabolic reactions.

Temperature-Increasing Mechanisms

Prevention of heat loss through skin vasoconstriction
Increase in thermogenesis (heat production) through shivering and increased metabolic reactions

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Description

This quiz covers the concept of body temperature, its regulation, and differences between core and skin temperatures. It also discusses normal body temperature ranges in humans.