Human Body Thermoregulation Quiz

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Questions and Answers

What is the normal range for oral temperature at rest?

37 ± 0.6°C (correct)

35.5°C to 36.8°C

36.5°C to 37.0°C

36.1°C to 37.5°C

What primarily ensures thermoregulation within the body?

Digestive system

Respiratory system

Nervous system (correct)

Endocrine system

What part of the hypothalamus is responsible for coordinating heat loss?

Lateral hypothalamus

Anterior hypothalamus (correct)

Medial hypothalamus

Posterior hypothalamus

What is the primary factor that contributes to the heat production in the body?

Muscles and viscera Signup and view all the answers

At what temperature do ice crystals begin to form in the human body?

-10°C Signup and view all the answers

What could happen to the body if heat loss did not occur during exertion?

Body temperature could increase by 20°C/h Signup and view all the answers

What is the primary cause of body temperature variations?

Circadian rhythm Signup and view all the answers

How does subcutaneous cellular tissue contribute to thermoregulation?

It transmits heat less efficiently than other tissues Signup and view all the answers

Where are the thermoregulation centers primarily located?

Posterior hypothalamus Signup and view all the answers

Which of the following factors does NOT influence the activity of thermoregulation centers?

External humidity levels Signup and view all the answers

What physiological response occurs when body temperature decreases?

Vasoconstriction and reduction of heat production Signup and view all the answers

What is the thermostatic reference point for body temperature regulation?

35.8°C to 37.4°C Signup and view all the answers

Which gland's hormones play a role in influencing thermoregulation?

Thyroid gland Signup and view all the answers

In terms of ages, how do body temperatures vary?

Young children have higher temperatures than older adults Signup and view all the answers

What happens to the body when temperatures exceed 41°C?

It signifies a failure in thermoregulation Signup and view all the answers

Which type of receptors are found in the anterior hypothalamus?

Temperature-sensitive neurons Signup and view all the answers

What percentage of heat loss occurs through radiation?

60% Signup and view all the answers

Which mechanism primarily involves the transfer of heat through air or vacuum?

Radiation Signup and view all the answers

Which factor does NOT affect heat loss during evaporation of water?

Oxygen levels Signup and view all the answers

What role does the sympathetic nervous system play in sweating?

It initiates the secretion of sweat. Signup and view all the answers

What is the primary method by which blood helps regulate heat loss?

By carrying heat to the skin surface Signup and view all the answers

Which term describes the heat loss mechanism of removing warm air from the skin surface?

Convection Signup and view all the answers

What does a drop in temperature trigger in the body's response system?

Negative feedback response Signup and view all the answers

What is one effect of anticholinergic drugs on heat loss?

They interfere with sweating. Signup and view all the answers

What is the primary effect of shivering on body temperature?

It increases heat production by 6-7 times. Signup and view all the answers

How does dehydration affect body temperature regulation?

It impairs the body's ability to regulate temperature. Signup and view all the answers

Which of the following hormones increases during cold exposure to aid in thermoregulation?

Adrenaline Signup and view all the answers

What physiological response occurs when the body temperature rises?

Decreased activity of piloerector muscles. Signup and view all the answers

What is the effect of physical effort on body temperature?

Increases body temperature by converting 3/4 of energy to heat. Signup and view all the answers

What role do arteriovenous shunts play in thermoregulation?

They allow blood to bypass tissues for heat conservation. Signup and view all the answers

Which mechanism reduces heat loss through the skin during cold exposure?

Sympathetic stimulation closing anastomoses. Signup and view all the answers

How is the metabolic rate affected by a temperature increase of 0.56°C?

It increases by approximately 7%. Signup and view all the answers

What is classified as mild hypothermia?

< 35°C Signup and view all the answers

Which of the following is NOT a risk factor for hypothermia?

Regular exercise Signup and view all the answers

What phase occurs when the internal body temperature drops to 35°C in immersion hypothermia?

Excitation Phase Signup and view all the answers

Endogenous hypothermia can occur at what ambient condition?

At normal ambient temperature Signup and view all the answers

Which contributing factor is associated with decreased capacity to conserve heat?

Hypothyroidism Signup and view all the answers

What is a potential local effect of cold exposure?

Cellular damage Signup and view all the answers

Impaired thermoregulation control can result from which condition?

Uremia Signup and view all the answers

What is a significant risk of the critical phase of hypothermia?

Ventricular arrhythmias Signup and view all the answers

What characterizes hypovolemic heat shock?

Internal temperature above 40°C and absence of sweating Signup and view all the answers

Which factors contribute to classical heat shock?

Immobility, inadequate hydration, and comorbidities Signup and view all the answers

What is the primary treatment for heat shock?

Placement in a cool area and hydration Signup and view all the answers

What occurs during the advanced stages of heat shock?

Decreased blood pressure and cardiac output Signup and view all the answers

Which group is at highest risk for exertional heat shock?

Athletes and individuals engaged in intense physical activity Signup and view all the answers

How does heat affect bodily cells?

It causes direct harm and releases endogenous pyrogens Signup and view all the answers

What is a potential consequence of acute circulatory failure during heat shock?

Multi-organ dysfunction syndrome with vital risks Signup and view all the answers

In the initial stages of heat shock, what happens to the cardiac output?

Cardiac output is initially increased Signup and view all the answers

Study Notes

Pathophysiology of the febrile reaction and acclimatization to temperature variation

The study covers the pathophysiology of febrile reaction and acclimatization to temperature variation.
Homeothermy involves maintaining a constant internal body temperature, regardless of ambient temperature fluctuations or physical exertion.
Normal body temperature is around 37 ± 0.6°C, with variations across different measurements (oral, rectal, axillary).
A typical oral temperature is approximately 36.7°C.
Rectal temperature readings are typically 0.5°C higher than oral readings.
Severe or prolonged physical effort can increase body temperature to 38°C.
The body's temperature fluctuates throughout the day, with lower values in the morning (around 3 a.m.) and higher values in the evening (around 6 p.m.).
Temperature is the difference between heat production and heat loss.
Thermoregulation is maintained by the nervous system, blood vessels, skin, and behavioral responses.
The hypothalamus regulates thermoregulation.

Homeothermy
Febrile reactions
Acclimatization to heat and hyperthermia
Acclimatization to cold and hypothermia
Local effects of cold

Body Temperature Regulation

The body's core (muscles and viscera) produce most of its heat. Subcutaneous tissues transmit heat one-third less efficiently than other tissues.
Heat transfer from the core to the skin occurs through blood circulation.
Without the mechanisms for heat loss, the human body would overheat by 10°C/h during exertion, and 20°C/h.
The hypothalamus (H) is the central thermoregulatory control center.
The anterior hypothalamus coordinates heat loss.
The posterior hypothalamus coordinates heat production.
There are receptors in the anterior hypothalamus and other areas, sensitive to heat and cold.

Thermoregulation Centers

Neurons in the anterior hypothalamus are irrigated by a rich vascular network called the OVLT.
Endothelial cells of the OVLT release arachidonic acid metabolites, producing fever.
The activity of thermoregulation centers is affected by various stimuli from the periphery, hormones (e.g., thyroxine, corticosteroids), catecholamines, and blood temperature.

Mechanisms for Adapting to Temperature Variations

For temperature decrease: vasodilation, sweating, decreased heat production.
For temperature increase: vasoconstriction, piloerection, increased heat production.
Temperatures outside the 35.8°C to 37.4°C range indicate a thermoregulation failure.

Factors Affecting Body Temperature

Age
Gender
Time of day
Physical activity
Environment
Illness
Hormones
Diet
Hydration
Sleep

Thermogenesis

The fight against cold is a chemical mechanism. Shivering increases heat production by 6-7 times.
Activation of the sympathetic system increases cellular metabolism, releasing adrenaline and noradrenaline when temperature drops, influencing cellular metabolism.
ATP production decreases, and heat production increases.
Hypothalamic TRH secretion increases thyroid hormones.

Thermolysis

Heat loss through the skin, primarily through arteriovenous shunts (like radiators).
Peripheral vasoconstriction directs blood from superficial to deeper tissues.
Heat loss through piloerection contractions, conduction, convection, radiation, evaporation, and respiration.

Blood Flow Control

Blood flow is regulated by the sympathetic nervous system.
Reducing the exchange surface area via piloerector muscle contraction reduces heat loss.
Heat loss occurs through conduction (3%), radiation (60%), convection (15%), and evaporation (insensible perspiration, 22%). Heating and humidifying inspired air and urine/feces contribute to heat loss.

Types of Fever

Intermittent: temperature returns to normal at least once a day, significant differences between morning and evening.
Remittent: temperature differences greater than 20°C between morning and evening and doesn't return to normal.
Continuous: temperature variations are less than 1°C.
Recurrent: episodes of fever alternating with periods of normal temperature.
Irregular: shows temperature variations of varying degrees and patterns.

ACCLIMATIZATION TO HIGH TEMPERATURES

Thermolysis is done via cutaneous vasodilation and sweating.
Decreasing skeletal muscle tone decreases thermogenesis.
Exceeding adaptation mechanisms results in hyperthermia.
Examples of heat-related illness include "heat stroke".

Heat Stroke

Prolonged exposure to direct sunlight and significant overheating.
Symptoms include headache, dizziness, nausea, and loss of consciousness.
Core temperature above 40°C. Absence of sweating.
Heat stroke is a severe thermoregulatory disorder resulting in a significantly high core temperature and lack of sweating.

ACCLIMATIZATION TO LOW TEMPERATURES

Thermolysis is reduced via cutaneous vasoconstriction.
Thermogenesis increases via increased skeletal muscle tone (shivering) and increased biological oxidation rate (catecholamines, thyroxine).
The circulatory changes respond to sympathetic stimulation.
Excessive adaptation leads to hypothermia.

Hypothermia

Defined as a decrease in body core temperature below 35°C.
Can be classified as mild, moderate, or severe based on temperature.
Risk factors include extreme age, homelessness, malnutrition, chronic alcoholism, mental illness, and use of sedative medication.
Pathogenesis involves excessive heat loss due to accidental exposure to cold, burns, increased blood circulation in the skin, or reduced metabolic rates.

Local Effects of Cold

Direct and indirect effects on cells and extracellular fluid.
Crystallization of water reduces cellular damage in tissues like ligaments and tendons.
Irreversible denaturation of cell membranes is caused by increased ionic concentration.
Blood vessel damage can lead to cellular ischemia and hypoxia.
Vasoactive mediates (like histamine) increase capillary permeability, leading to water retention in interstitium and extensive tissue changes.

Hyperthermia

A condition characterized by a progressive increase in internal body temperature without any changes to the set point of thermoregulatory centers.
This disorder can be caused by exposure to a high-temperature external environment (exogenous), or arise internally (endogenous).
Different types include heat cramps, heat exhaustion, heat syncope, and heat stroke.

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Description

Test your knowledge on how the human body regulates temperature with this quiz. Learn about factors influencing thermoregulation, temperature variations, and the physiological responses involved. Perfect for students studying human physiology or related fields.