4) Body Temperature: Physiology Flashcards
1
Q
What determines body temperature?
A
- The difference between heat produced by body processes
- And the amount of heat lost to the external environment
2
Q
How do temperature control mechanisms work?
A
- They keep the body’s core temperature relatively constant
- Despite environmental extremes and physical activity levels
3
Q
How does body surface temperature differ from core temperature?
A
- Surface temperature fluctuates
- Depending on blood flow to skin and heat lost to environment
4
Q
What is the acceptable body temperature range?
A
- 36°C to 38°C
- A narrow range for optimal tissue/cell function
5
Q
What is the aim when measuring body temperature?
A
- To obtain average temperature of core body tissues/organs
6
Q
Which temperature measurement sites reflect core temperature?
A
Rectum
Tympanic membrane
Temporal artery
Esophagus
Pulmonary artery
Urinary bladder
Nasopharynx
7
Q
Which sites reflect surface temperature?
A
Skin
Mouth
Axillae
8
Q
Can temperature values differ between measurement sites?
A
- Yes, values may differ between sites
9
Q
What should nurses recognize about temperature readings?
A
- No single reading is normal for all people
- Learn the temperature range for individual patients
10
Q
How is body temperature regulation controlled?
A
- Thermoregulation is regulated by physiological and behavioral mechanisms
- The balance between heat production and heat loss must be closely maintained
11
Q
What controls body temperature regulation?
A
- The hypothalamus controls body temperature like a thermostat
- The anterior hypothalamus controls heat loss, the posterior controls heat production
12
Q
How does the anterior hypothalamus regulate temperature?
A
- When heated above set point, it sends impulses to reduce body temperature
- Mechanisms include sweating, vasodilation, inhibiting heat production
13
Q
How does the posterior hypothalamus regulate temperature?
A
- When body temperature is below set point, it institutes heat conservation
- Mechanisms include vasoconstriction, muscle contraction, and shivering
14
Q
What can disrupt temperature regulation?
A
- Disease or trauma to the hypothalamus or spinal cord
- Can cause serious alterations in temperature control
15
Q
What is the basis for heat production in the body?
A
- Heat is produced as a by-product of metabolism in all body cells
- Food is the primary fuel source for metabolism
16
Q
How does activity level affect heat production?
A
- Additional chemical reactions from activities increase metabolic rate
- As metabolism increases, more heat is produced
17
Q
What processes produce heat in the body?
A
- Heat production occurs during rest, voluntary movements, shivering, nonshivering thermogenesis
18
Q
What is basal metabolism?
A
- Accounts for heat produced by the body at absolute rest
- Average basal metabolic rate depends on body surface area
19
Q
How do thyroid hormones affect heat production?
A
- Promote breakdown of glucose and fat, increasing metabolic rate
- Large amounts can increase basal metabolic rate by 100%
20
Q
How does gender affect basal metabolic rate?
A
- Testosterone increases basal metabolic rate
- Men have a higher basal metabolic rate than women
21
Q
How does exercise affect heat production?
A
- Voluntary movements like exercise require additional energy
- Metabolic rates can increase up to 2000 times normal during exercise
22
Q
What is shivering and how does it produce heat?
A
- Involuntary muscle movement in response to temperature differences
- Skeletal muscle movement requires significant energy, increasing heat production
23
Q
Who is at increased risk for hypothermia related to heat production?
A
- Newborns and older persons are less able to shiver or vasoconstrict
- Puts them at increased risk for hypothermia
24
Q
What is nonshivering thermogenesis?
A
- Occurs primarily in newborns as main heat source due to inability to shiver
- Stimulates fat metabolism to produce internal heat
25
How does heat loss occur in the body?
- Through radiation, conduction, convection, and evaporation
- Due to skin's structure and exposure to environment
26
What is radiation heat loss?
- Transfer of heat from body surface to environment without direct contact
- Up to 85% of body surface area radiates heat
27
How does vasodilation/vasoconstriction affect radiation heat loss?
- Vasodilation increases blood flow to skin, increasing radiant heat loss
- Vasoconstriction minimizes radiant heat loss
28
What factors increase radiation heat loss?
- Removing clothing/blankets
- Standing position exposes more surface area
- Temperature difference between body and environment
29
How can radiation heat loss be reduced?
- Fetal position minimizes exposed surface area
- Wearing dark, closely woven clothing
30
What is conduction heat loss?
- Transfer of heat through direct contact with solids/liquids/gases
- Normally accounts for small amount of heat loss
31
How can conduction heat loss be increased/decreased?
- Applying cool cloths increases conductive loss
- Layering clothing reduces conductive loss
32
What is convection heat loss?
- Transfer of heat away from body by air movement
- Fans promote convection heat loss
33
What increases convection heat loss?
- Moistened skin coming into contact with moving air
34
What is evaporation in relation to heat loss?
- Transfer of heat energy when liquid changes to gas
- Body continuously loses heat through evaporation
35
How much water/heat is lost through evaporation daily?
- About 600-900 mL evaporates from skin and lungs
- Resulting in water and heat loss
36
How does the body promote additional evaporative heat loss?
- By regulating perspiration (sweating)
- Sweat glands in skin secrete sweat that evaporates
37
What triggers sweat gland secretion?
- When body temperature rises
- Anterior hypothalamus signals sweat glands to release sweat
38
When does sweating occur to lose excessive heat?
- During exercise
- During emotional or mental stress
39
What is diaphoresis?
- Visible perspiration
- Occurs primarily on forehead and upper thorax
40
What can excessive evaporation cause?
- Skin scaling and itching
- Drying of nares and pharynx
41
How does lowered body temperature affect sweating?
- Inhibits sweat gland secretion
42
Who cannot tolerate warm temperatures due to impaired sweating?
- Those with congenital absence of sweat glands
- Those with skin diseases impairing sweating
43
How does the skin help regulate body temperature?
- Insulates the body
- Controls blood flow/heat loss through vasoconstriction/vasodilation
- Provides temperature sensation
44
What provides insulation to keep heat inside the body?
- Skin
- Subcutaneous tissue
- Body fat
45
Who has more natural insulation?
- People with more body fat
- Compared to slim/muscular people
46
Where is heat produced in the body?
- Internal organs
- Amount increases during exercise/sympathetic stimulation
47
How does blood carry heat to the skin surface?
- Blood flows from internal organs carrying heat
- To well-vascularized areas like hands, feet, ears
48
How much blood can flow through vascular skin areas?
- May vary from minimal to 30% of heart's output
49
How is heat lost from the skin surface?
- Heat transfers from blood vessels to skin surface
- Then lost to environment through heat loss mechanisms
50
What determines blood flow and heat loss to skin?
- Degree of vasoconstriction
51
How does the body respond to high core temperature?
- Hypothalamus inhibits vasoconstriction
- Blood vessels dilate, increasing blood/heat to skin surface
52
How does the body respond to low core temperature?
- Hypothalamus initiates vasoconstriction
- Reducing blood flow/heat loss to skin to conserve heat
53
What allows healthy individuals to maintain comfortable body temperature?
- Voluntarily acting when exposed to temperature extremes
- Ability depends on degree of temperature extreme
54
What abilities are needed to control body temperature?
- Sensing feeling comfortable/uncomfortable
- Intact thought processes and emotions
- Mobility to remove/add clothes
55
Who may have difficulty controlling body temperature?
- Those lacking the required abilities
- Infants, older adults, spinal cord injuries
56
What can impair temperature control?
- Illness
- Altered consciousness
- Impaired thought processes
57
How effective are behavioral changes in extreme temperatures?
- Have limited effect on controlling temperature
- Like removing/adding clothes
58
What is important for nurses regarding thermoregulation?
- Assessing factors that place patients at high risk
- For ineffective thermoregulation
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