Thermoregulation Flashcards
What are the main processes responsible for heat production in the body? 7
Metabolism (glycolysis), voluntary actions (physical activity), shivering, brown fat metabolism, vasoconstriction, piloerection, and neuroendocrine regulation.
How does the body lose heat through sweating?
Eccrine sweat glands secrete sweat, which evaporates from the skin surface, causing heat loss.
What are the primary methods of heat loss in the body?
Conduction/convection (60%), radiation (25%), and evaporation (15%).
What is the role of the hypothalamus in temperature regulation?
The hypothalamus maintains core temperature by adjusting metabolic and autonomic responses.
What is core temperature, and why is it important?
Core temperature is the internal body temperature, essential for enzymatic reactions and bodily functions.
How does fever (pyrexia) develop in response to an infection?
Pyrogens induce PGE2 release in the hypothalamus, raising the body’s set temperature.
What is the difference between fever and hyperthermia?
Fever results from an altered hypothalamic set point, while hyperthermia occurs due to excessive heat production or environmental exposure.
What are common treatments for fever?
Paracetamol, NSAIDs, aspirin, cooling methods, and exposure to fans.
What are the classifications of body temperature?
Hypothermia (<35°C), normal (36.5-37.5°C), fever (>37.5 or 38.3°C), hyperpyrexia (>40 or 41.5°C).
What are the primary causes of hyperthermia?
Exertion, situational factors, drugs, and pyrexia.
What is the most significant method of heat loss in the human body?
Conduction/convection
Which of the following processes is responsible for heat production in neonates?
Brown fat metabolism
Where is the primary temperature control center in the brain?
Hypothalamus
Which of the following is NOT a cause of hypothermia?
Increased metabolic rate
How do pyrogens induce fever?
By stimulating the release of PGE2 in the hypothalamus
What physiological response is responsible for increasing heat loss when the body is overheating?
Vasodilation
Which of the following treatments is NOT typically used to reduce fever?
Beta-blockers
What happens to enzymatic activity when temperature increases by 10°C?
It increases by 2.5 times
What is a life-threatening level of hyperthermia?
41.5°C
What is the primary mechanism by which antipyretic drugs like aspirin reduce fever?
Blocking the production of PGE2
Why do biological systems operate under a tight range of conditions?
Enzymes and metabolic processes require a stable environment for optimal function.
How does a 10°C increase affect enzymatic activity?
It increases enzymatic activity by approximately 2.5 times.
At what temperature does protein denaturation occur?
Above 45°C.
What is the functional temperature range for “conscious intelligence”?
Between 35 – 40°C.
How does core temperature compare to skin temperature?
Core temperature is approximately 0.5°C higher than skin temperature.
How does core temperature change throughout the day?
It is lowest just before waking up and rises as the day progresses.
How does the menstrual cycle affect core temperature?
It increases by about 0.5°C at ovulation.
Why is temperature relevant in fertility investigations?
Tracking ovulation temperature changes can help assess fertility.
What are the different types of temperature measurement methods?
Thermometer, skin temperature thermometer, tympanic (ear) thermometer, oesophageal thermometer, and rectal temperature.
Which temperature measurement is commonly used in children?
Skin temperature thermometer, often on the scalp.
How does a tympanic thermometer work?
It uses infrared technology to measure temperature in the ear.
Where are temperature receptors found in the body?
Skin, GI tract, great veins, and hypothalamus.
What type of neurons are temperature receptors?
Specialized outgrowths of neurons.
Are there more hot or cold receptors in the skin?
There are 10 times more cold receptors than hot receptors.
Which nerve fibers are involved in temperature sensation?
Aδ and C fibers.
Which part of the brain predominantly controls body temperature?
The anterior hypothalamus.
What is the function of the “set point” thermostat in the hypothalamus?
It regulates the body’s core temperature to maintain homeostasis.
What are the two main systems involved in temperature regulation?
Heat-increasing mechanisms and heat-loss mechanisms.
hy are extreme ages more prone to hypo/hyperthermia?
They may lack the ability to regulate clothing or move to adjust temperature.
How do incubators help newborns?
They maintain a controlled temperature environment.
How does metabolism contribute to heat production?
The respiratory cycle generates heat as a byproduct.
How much can shivering increase heat production?
Up to 5 times the normal rate.
Where does shivering predominantly occur?
The trunk.
Why is shivering metabolically expensive?
It requires significant energy and oxygen consumption.
What is the function of brown fat in heat production?
It generates heat through ß3 receptor-mediated metabolism.
In which populations is brown fat most relevant?
Neonates and some animals.
What paradoxical effect can prolonged cold exposure cause?
: Increased blood flow to the skin.
What controls piloerection?
Sympathetic nervous system.
What hormones are involved in neuroendocrine thermoregulation?
Catecholamines (adrenaline/noradrenaline) and potentially thyroxine.
What are the three main methods of heat loss?
Conduction/convection (60%), radiation (25%), and evaporation (15%).
How does sweating help in heat loss?
It evaporates from the skin, carrying heat away.
What is the normal daily sweat production?
Up to 1000 ml/day
How does acclimatization affect sweating?
It increases sweat production to 2000 ml/day.
Why does urea concentration increase near the skin surface?
It contributes to body odor.
How do animals lose heat without sweating?
By panting and ventilating their dead space.
What is hypothermia?
A core temperature below 35°C.
When is hypothermia considered severe?
When core temperature falls below 28°C.
What are common causes of hypothermia?
Behavioral factors, hypothyroidism, dermatological conditions, and sepsis.
What are clinical features of hypothermia?
Confusion, coma, and cardiovascular collapse
How is hypothermia managed?
ABC assessment, controlled warming (Bear hugger, tin foil, cardiopulmonary bypass).
What is the temperature threshold for hyperthermia?
> 38°C.
When is hyperthermia life-threatening?
When core temperature exceeds 40°C.
What are the clinical signs of hyperthermia?
Confusion, seizures, coma, and cardiovascular collapse.
What causes pyrexia?
An altered hypothalamic set point.
What are common causes of fever of unknown origin?
Infection, blood transfusion reactions, inflammation, malignancy, and hypothalamic damage.
What physical methods can reduce fever?
Tepid sponging, cooling packs, ice, exposure, and fans.
