Thermoregulation and pyrexia

Question 1

How is enzymatic activity affected by temperature?

Answer 1

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

Question 2

What is basal metabolism?

Answer 2

Energy body requires to maintain homeostasis

Question 3

When does enzyme denaturing occur?

Answer 3

Above 45 degrees

Question 4

What is the range of normal temperature?

Answer 4

35 degrees to 37.5

Question 5

Where is heat concentrated when cold?

Answer 5

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

Question 6

Where is heat lowest when hot?

Answer 6

Surface of skin and hands and feet.

Question 7

What is an unreliable indicator of body temperature?

Answer 7

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

Question 8

What is diurnal variation?

Answer 8

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

Question 9

How does ovulation affect body temperature?

Answer 9

Increases basal body temperature by 0.5 degrees

Question 10

What is the temperature range for women?

Answer 10

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

Question 11

What is the temperature range for men?

Answer 11

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

Question 12

Where can body temp be measured/

Answer 12

Oral, tympanic (ear), rectum, axilla

Question 13

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

Answer 13

Tympanic and axilla area

Question 14

Where is body temperature regulated?

Answer 14

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

Question 14

Which receptors respond to extremes of body heat?

Answer 14

Nociceptors, due to extreme temperatures causing noxious stimuli

Question 15

What are thermoreceptors?

Answer 15

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.

Question 16

When are cutaneous thermoreceptors for heat activated?

Answer 16

Temperature between 29 to 45 degrees, greatest activity at 45

Question 17

When are cutaneous thermoreceptors for cold activated?

Answer 17

More numerous in the skin below 29 degrees

Question 18

What is the temp range for oral and rectal?

Answer 18

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

Question 19

What is hypothermia?

Answer 19

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

Question 20

What is the critical point for hypothermia?

Answer 20

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.

Question 21

How is hypothermia managed?

Answer 21

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

Question 22

What are the features of hypothermia?

Answer 22

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

Question 23

What is hyperthermia?

Answer 23

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

Question 24

How is heat lost by the body when hot?

Answer 24

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

Question 25

What is brown fat?

Answer 25

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.

Question 26

What is the significance of shivering/

Answer 26

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

Question 27

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

Answer 27

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

Question 28

How does piloerection occur?

Answer 28

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

Question 29

How is heat lost by the by the body?

Answer 29

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

Question 30

What are the methods of heat loss?

Answer 30

Panting, sweating, vasodilation

Question 31

How is the majority of heat lost in the body?

Answer 31

Conduction and convection

Question 32

How does sweating occur?

Answer 32

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.

Question 33

What is hyperthermia?

Answer 33

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

Question 34

What are the features of hyperthermia?

Answer 34

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

Question 35

What is pyrexia?

Answer 35

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

Question 36

What causes pyrexia?

Answer 36

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

Question 37

What is pyrogenesis?

Answer 37

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

Question 38

How is pyrexia treated?

Answer 38

Paracetomol, NSAIDS, cooling packs, ice