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Year 2 > Thermoregulation and pyrexia > Flashcards

Thermoregulation and pyrexia Flashcards

1
Q

How is enzymatic activity affected by temperature?

A

Increases by up to 2.5x when there is an increase in temperature by 10 degrees due to greater kinetic energy. Decreased enzymatic activity by drop in core body temp by 10 degrees

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2
Q

What is basal metabolism?

A

Energy body requires to maintain homeostasis

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3
Q

When does enzyme denaturing occur?

A

Above 45 degrees

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4
Q

What is the range of normal temperature?

A

35 degrees to 37.5

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5
Q

Where is heat concentrated when cold?

A

Head and trunk and temperature decreases further from the trunk, with Distal hands and feet and skin being the lowest.

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6
Q

Where is heat lowest when hot?

A

Surface of skin and hands and feet.

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7
Q

What is an unreliable indicator of body temperature?

A

Skin is 4 degrees lower than body temperature because heat loss is greater. THermoreceptors on the skin are more sensitive to the cold

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8
Q

What is diurnal variation?

A

Body temperature pattern every 24 hours. Body temp is lowest at 5am and steadily rises to peak at 5pm and drop again.

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9
Q

How does ovulation affect body temperature?

A

Increases basal body temperature by 0.5 degrees

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10
Q

What is the temperature range for women?

A

Greater range of body temper which is generally lower than men basal body temperature excluding the oral region.

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11
Q

What is the temperature range for men?

A

Narrower range than women with a generally higher basal body temperature in most areas of the body.

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12
Q

Where can body temp be measured/

A

Oral, tympanic (ear), rectum, axilla

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13
Q

Where is basal body temperature the same for men and women?

A

Tympanic and axilla area

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14
Q

Where is body temperature regulated?

A

Hypothalamus which alters blood vessels, glands and hair follicles to return body temperature to set point

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14
Q

Which receptors respond to extremes of body heat?

A

Nociceptors, due to extreme temperatures causing noxious stimuli

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15
Q

What are thermoreceptors?

A

Dermis, GI tract, great veins and hypothalamus. They have specialised nerve endings in the form of a-delta and c-fibres to transmit information to the hypothalamus. They fire continuously at constant body temperature but rate changes when there is a change to the normal range.

16
Q

When are cutaneous thermoreceptors for heat activated?

A

Temperature between 29 to 45 degrees, greatest activity at 45

17
Q

When are cutaneous thermoreceptors for cold activated?

A

More numerous in the skin below 29 degrees

18
Q

What is the temp range for oral and rectal?

A

Oral has a greater range with 32 -38 degrees. Rectal has a range of 34-37.

19
Q

What is hypothermia?

A

Drop in core body temperature below 35 degrees which leads to change in mental status, motor impairment, arrythmia. Can be caused by hypothyroidism.

20
Q

What is the critical point for hypothermia?

A

Below 28 degrees where the hypothalamus is unable to regulate core body temperature independently and chemical heat production in cells. Leads to CNS depression into coma.

21
Q

How is hypothermia managed?

A

Controlled warming with foil blanket and ABC (airways, breathing, and circulation)

22
Q

What are the features of hypothermia?

A

Confusion, coma and cardiovascular collapse. When especially severe, causes vasodilation to warm the limbs.

23
Q

What is hyperthermia?

A

Core body temp above 38 degrees which becomes critical at 40 degrees. Typically exertional but can be caused by pyrexia or drugs

24
Q

How is heat lost by the body when hot?

A

Conduction: heat transfer through direct touch
Convection: heat transfer via fluid movement
Radiation
Evaporation via sweating and panting
Majoiriy of heat is lost via conduction and convection

25
Q

What is brown fat?

A

Formed of mitochondrial rich adipocytes which are activated in cold temperatures to cause glucose and fat breakdown to generate heat. However levels in adult humans are very low and have little effect. Present primarily in animals and neonates, regulated by Beta-3 receptor.

26
Q

What is the significance of shivering/

A

Mostly truncal and metabolically expensive, but increases heat production up to 5x

27
Q

What hapens to blood vessels when there is prolonged cold exposure?

A

Initially there is vasoconstriction to divert blood flow to the critical organs and blood vessels are mediated by the sympathetic system. However, eventually vasodilation will occur

28
Q

How does piloerection occur?

A

Contraction of smooth muscles by the sympathetic nervous system which have minimal efficacy

29
Q

How is heat lost by the by the body?

A

Conduction: transfer via direct contact
convection: transfer due to fluid movement
radiation
and evaporation

30
Q

What are the methods of heat loss?

A

Panting, sweating, vasodilation

31
Q

How is the majority of heat lost in the body?

A

Conduction and convection

32
Q

How does sweating occur?

A

Eccrine glands are located in the dermis and release secretions of protein free Na+ and H20 via sympathetic stimulation and open up into pore on epidermis. Greatest heat loss occurs due to this up to 10x. When acclimatised, increases amount of secretions.

33
Q

What is hyperthermia?

A

Above 38 degrees due to excess physical exertion in humid weather, especially in the elderly. Also caused by pyrexia when ill beyond the already increased set point

34
Q

What are the features of hyperthermia?

A

Confusions, seizures, coma. Vasodilation results in low BP, sweat results in blurred vision and dizziness and may lead to cardiovascular collapse

35
Q

What is pyrexia?

A

Occurs due to altered set point where there is vasodilation, piloerection, sweating and epinephrine release

36
Q

What causes pyrexia?

A

Infection, hypothalamic insult (injury), malignancy, blood transfusion which is iatrogenic pyrogen

37
Q

What is pyrogenesis?

A

Pyrogen induces production of inflammatory mediators and increase in cAMP and Ca2+ levels

38
Q

How is pyrexia treated?

A

Paracetomol, NSAIDS, cooling packs, ice

Year 2 (247 decks)

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