6.2 Temperature Regulation Flashcards
To maintain body temperature within certain limits
Homeostasis
Process controlling the balance between heat production and heat loss
Thermoregulation
Normal body temperature is also known as
Normothermia or Euthermia
Note: optimal condition for cellular activity
Commonly accepted average core temperature
37.0 C or 98.6 F
5 major mechanisms of heat production
- Basal metabolic rate (BMR)
- Muscle activity
- Metabolic effect of hormones (Thyroxine, GH, Testosterone, NE, E)
- Increased sympathetic activity
- Thermogenic effect of food
T/F The most metabolically active produce the least heat
False- produce the MOST HEAT
When do visceral organs produce the most heat
At rest
Note: approximately 70% of heat is produced by visceral organs during rest
Increased metabolism of _________ produces ________ times more heat than the rest of the body
Skeletal muscle; 30-40
Involuntary muscle contraction that is usually a response to cold
Shivering
Hormones involved in heat gain
Thyroxine (response to cold exposure) GH Testosterone Epinephrine Norepinephrine
___(1)___ releases TRH -> stimulates pituitary gland to release ____(2)____ -> stimulates thyroid to increase ____(3)____ output
- Hypothalamus
- Thyrotropin
- Thyroxine
Increased cellular metabolism leads to
Heat
Causes a decrease in the radiation of heat from skin
Skin vasoconstriction
Increased metabolic rate leads to the following adrenergic effect
Increased HR
Increased respiration
Increased blood glucose levels
Mechanism of piloerection
Contraction of arrector pili muscle
-> brings hair upright -> traps a layer of warm air on the skin -> extra insulation
Provides heat to infants to prevent death from hypothermia
Brown adipose tissue (BAT)
Characteristics of brown fat (4)
- Dark color
- Enriched blood supply
- Dense cellular content
- Abundant sympathetic nerve endings
__(1)__ from BAT sympathetic nerves is released -> __(2)__ are metabolized -> heat
- Norepinephrine
2. Triglycerides
T/F When you eat food, the body expends energy
True
T/F Eating food raises basal metabolic rate
True
Note: digestion of food, processing, and absorption of nutrients raises BMR
Greatest increase in rate at which the body burns calories happens when what type of diet is taken
High protein
Flow of transfer of body heat
Deep organs and tissues -> skin -> air and surroundings
4 major mechanisms of heat loss
- Radiation
- Convection
- Conduction
- Evaporation
Loss of heat via infrared waves
Radiation
Approximately how much of body heat is lost by radiation
60%
Direction of energy flow
Warmer to cooler
Conduction is heat transfer between objects in ________
Direct contact
Examples of highly conductive surfaces for heat conduction
Metal and rock
T/F Low conductive surfaces conduct heat away from the body
False- Highly conductive surfaces
Body loses heat about 25 times faster in __(1)___ than in ___(2)___
- Water
2. Air
Transfer of heat by movement of the hot particles to cooler areas
Convection
__(1)__ tends to rise and expand while __(2)__ falls
- Warm air
2. Cool air
Substantially enhances heat exchange from the body surface to the air
Convection
T/F Convection is enhanced by anything that moves air more rapidly across body surface
True
Note: reason behind the use of fan to cool off
Insulating warm air layer that forms around the skin
Epiclimate
Note: forms under windless conditions
Mechanism behind wind chill
Wind disrupts epiclimate -> increase rate at which body loses heat
T/F Abrupt transition from body temperature to air temperature means a steep thermal gradient
True
Evaporation is the loss of heat by
Evaporation of water
Approximate amount of water evaporating from lungs and skin
800mL/day or 480kcal/day
T/F insensible water loss accompanied by insensible heat loss is significant
False- NOT significant
Evaporation becomes sensible heat loss when
Body temperature rises
Intense exercise raises the body temperature by
2C to 3C
__(1)__ L/hour of perspiration evaporated results to __(2)__ kcal heat removed per hour
- 1-2 L/hour
2. 2000 kcal
Outer parts of the body (skin and subcutaneous tissue) that change temperature depending in the surroundings
Shell or superficial
Consist of the thermo-regulated deep tissues of the body and the proximal extremities
Core or internal
Note: normally remains almost constant
2 important elements of a thermometer
- Temperature Sensor
2. Scale
4 sites for temperature measurement
- Anus (rectal temp)
- Mouth (oral temp)
- Underarm (axillary temp)
- Ear (tympanic temp)
Sites to get core temperature
- Oral/mouth
- Rectal/anus
- Gut
What type of temp is measured in axillary and other skin-based temperatures
Shell temperature
0-2 years old : ____(1)____
_____(2)_____ : 36.1C - 37.8C
_____(3)_____ : 35.9C - 37.6C
> 65 years old : ____(4)____
- 36.4C - 38.0C
- 3-10 y.o.
- 11-65 y.o.
- 35.8C - 37.5C
Oral temperature is influenced by
- Drinking
- Chewing
- Smoking
- Breathing with mouth open
T/F Axillary temperature is the longest and most accurate method
False- most INACCURATE method
Generally considered the most accurate route of body temperature measurement
Rectal temperature
T/F Tympanic temperature correlates closely with core temperature
True
Note: tympanic membrane receives BS from carotid artery which is in close proximity to hypothalamus
Thermostat center of the body
Hypothalamus
Role of hypothalamus in heat regulation
- Sensory center
2. Integration center
Central thermoreceptors are mainly in ________
Preoptic area of hypothalamus
Skin thermoreceptors that mediate neutral, cool, and cold sensations (5C - 45C)
Cold receptors
Skin thermoreceptors activated when temp is from 30C - 50C
Warm receptors
T/F there are 10 times more cold receptors than heat receptors
True
______ establishes a “set-point” for the internal body temperature
Hypothalamus
If the two temperatures do not match -> hypothalamus activates heat generation or heat loss mechanism -> adjust ___(1)____ until ___(2)___ is achieved
- Core temperature
2. Set-point
Two nuclei of the hypothalamus that are involved in heat regulation
- Preoptic area (POA)
- Anterior hypothalamus (AH)
Note: treated as one area = POA/AH
T/F POA/AH monitors its own CNS temperature and receives input from skin receptors
True
Compares the detected core temperature to the set-point temperature
POA/AH
Damage to POA/AH results to
Hyperthermia
________ hypothalamus helps integrate sensory inputs from BOTH central and peripheral thermoreceptors
Posterior
Anterior hypothalamus: ______
Posterior hypothalamus: heating up
Cooling down
POA/AH : __(1)__
___(2)___: hypothermia
- Hyperthermia
2. Posterior hypothalamus
3 important mechanism to reduce body heat
- Vasodilation of skin blood vessels
- Sweating
- Decreased heat production
_____ environment increases core temperature
Hot
T/F Passive vasodilation decreases blood flow through anastomoses (AVA)
False- INCREASES
Decreases in core temperature via evaporative cooling at skin surface
Sweating
Sweating is controlled from a center in the _____ of the hypothalamus
POA/AH
Sweat glands are innervated via
Cholinergic sympathetic fibers
Sweat is formed in _____ portion of sweat glands
Coiled secretary
Note: electrolyte content similar to plasma
Filtrates from sweat passes through the _______
Uncoiled duct
Note: Na and Cl are reabsorbed
Final sweat extruded thru the skin pores are _________ to plasma
Hypotonic
When the body is exposed to prolonged heat, electrolyte levels may fall and cause ___________
Systemic dehydration
Increase in ________ diminishes loss of salt
Aldosterone
Process of adjusting to gradual change in environment
Acclimatization
T/F An unacclimatized person sweats profusely resulting to large amounts of sodium lost
True
After acclimatization, sweating begins earlier at a ______ core temperature
Lower
T/F an unacclimatized person sweat profusely but secrete sweat with low sodium concentration
False- acclimatized
Corrective mechanisms on a cold day
- Vasoconstriction of arterioles near skin’s surface
- Decrease production of sweat
- Increase metabolic rate
- Shivering
T/F Cognitive control of body temp involves conscious voluntary acts to adjust physical characteristics of the air-skin interface
False- Behavioral control
Ex. Fanning oneself on a hot day
Stretching out body : ___(1)___
_______(2)_______ : heat gain
- Heat loss/cooling
2. Curling up body
Body loses its ability to cool itself
Heat stroke
Note: symptoms High temp No sweating Hot, dry, red skin Rapid pulse Confusion, irritability, disorientation, hallucination Seizures Loss of consciousness/coma Death
In heat stroke, the internal body temp rises to as high as ______
40.5C or 105F
Milder form of heat illness
Heat exhaustion
Note: caused by prolonged exposure to high temp and dehydration
T/F there is a normal thermoregulatory system in a person experiencing heat stroke
False- heat exhaustion
Management of heat exhaustion
Salt and water replacement
Rest
2 types of heat exhaustion
- Water depletion (excessive thirst, weakness, headache, and loss of consciousness)
- Salt depletion (nausea and vomiting, muscle cramps and dizziness
Heat exhaustion : ___(1)___ pupils
Heat stroke : ___(2)___ pupils
- Dilated
2. Constricted
Painful, brief muscle cramps during exercise in a hot environment
Heat cramps
Note: involves the muscles for heavy work
T/F heat cramps is probably due to electrolyte loss
True
Core temp drops below 35.0C or 95.0F
Hypothermia
Note: may also be caused by injury to posterior hypothalamus
T/F in treating hypothermia restore warmth rapidly
False- Slowly
Note: do not immerse in warm water for rapid warming can cause heart arrhythmia
T/F In treating hypothermia, warm the person’s trunk first before hands and feet
True
Note: warming extremities first can cause shock
State of elevated core temp, which is often, but not necessarily, part of the defensive response of multicellular organisms to the invasion of pathogens
Fever/pyrexia
Fever in adults
Oral temp : ___(1)____
Rectal temp : ___(2)____
- Above 37.8C
2. Above 38.3C
T/F A child with fever has a rectal temp of 38.0C and higher
True
T/F injury or compression by tumor to the posterior hypothalamus can cause fever
False- preoptic area of hypothalamus
Substance that induces fever
Pyrogen
Note: may either be internal (endogenous) or external (exogenous)
_____ in the cell wall of some gram positive bacteria are exogenous pyrogen
Lipopolysaccharide (LPS)
Sudden resetting of the hypothalamic thermostat to higher level results to a lag between blood temp and the new hypothalamic set-point. This causes
Shivering chills
T/F when body temp catches up with new higher set-point, the person no longer experiences chills
True
Benefits of fever
- Increased antibody production
2. Inhibition of pathogen growth
Mechanism of aspirin
Inhibits COX -> inhibits Prostaglandin E2 production -> decrease set-point temp -> activate mechanisms of heat loss
