REGULATION OF BODY TEMERATURE Flashcards Preview

Pathology block 1 > REGULATION OF BODY TEMERATURE > Flashcards

Flashcards in REGULATION OF BODY TEMERATURE Deck (43)
1

What does ‘Homeothermic’ mean?

Homeothermic: capable of maintaining body temperature
within very narrow limits

2

Describe what it means to be homeothermic wrt humans

  • -Relative constant high core body temperature (~37oC)
  • -Frees Biochemical reaction
  • -Precise regulatory mechanism
  • -Highly elevated temperature leads to nerve malfunction, protein denaturation etc.
  • -Upper limit ~43oC

3

What is used as an estimate of core temperature?
(core = internal organs)

-Rectal temperature

4

the temperature of the body that reflects most accurately that of the cores is where?

 the esophagus (at the cardia)

5

Normal Body Temperature (Core) can vary due to: (2) name and describe

-EXOGENOUS FACTORS: Internal temperature can vary few degrees depending on activity patterns and external temperature

-ENDOGENOUS FACTORS: (e.g., progesterone) can increase body temperature

6

WRT exogenous agents, what are some of the variations that can take place?

  • climatogical environment
  • peripheral insulation
  • diet
  • physical activity
  • drugs

7

What are some normal core endogenous temperatures?

  • circadian rhythms
  • gender
  • age and body size
  • subcutaneous insulation
  • water content
  • psychological state

8

2. How is heat lost or gained?

  • metabolism
  • radiation
  • conduction
  • convection

9

Total energy expenditure equals what?

Internal heat produced +External work performed +Energy stored

10

What are channels of heat transfer?

  • conduction
  • convection
  • radiation
  • evaporation

11

Define radiation

Heat transmitted via emitted electromagnetic waves (infrared heat rays). All objects emits radiation.

12

Define conduction

Heat transfer by conduction occurs within a solid or between two or more solids in close contact.

13

wrt clothing (dry or wet) which increases heat loss 

wet clothing increases conduction of heat -increase heat loss

14

Define convection

Heat transfer by convection occurs in a fluid or between a fluid (gas) and a solid, providing a temperature gradient exist

15

describe the difference between conduction and convection

Differs from conduction in that the fluid or gas can be moving and therefore heat is not only transferred but displaced.

16

Describe how Convection currents work. What influences them?

carries away saturated air layer near skin

(influenced by the thickness of the thermal boundary).

17

Define evaporation

 Heat transfer occurs by means of a change in state, from a liquid to a gas.

18

Describe how evaporation takes place wrt energy

The transformation of water into water vapor requires energy

The amount of energy vaporise 1g of water is 0.685 kcal or 2.86 kJ.

(Latent heat of vaporization).
constant evaporation insensible heat loss (50ml/hr)

During severe exercise 1600 ml/hr heat loss by vaporization varies from 30 - 900 kcal/hr

19

What are the Factors affecting evaporation?

 Humidity: dry air increases evaporation;

Humid air decreases evaporation

20

Describe “Zone of Thermal Neutrality”

The range of ambient temperature in which the body maintains its heat balance without increasing either heat production or heat loss above their minimum level 

21

Describe how surface area and volume affect heat loss

Higher the ratio (SA/V),

Higher the heat loss

22

The lower temperature of the extremities (e.g., Finger, ear etc) in a windless environment reflects what? what happens wrt heat?

 large SA/V ratio (of the limb) relative to the trunk

very high heat loss

23

3. Regulation and control of core body temperature

skin temperature regulation begins with peripheral thermoreceptors

Core temperature regulations begins with central thermoreceptors

24

Describe the shivering and non-shivering roles wrt heat

Hypothalamus involves an involuntary motor responses to cause shivering skeletal muscles

hypothalamus involves sympathetic nerves to cause non-shivering via the adrenal medulla, sweat  gland and skin arterioles

25

What is the hypothalamus?

 serves as the primary overall integrator of reflexes

It is the brain's inner thermostat

26

Thermoreceptors come in two forms- name and describe

Warm fibers: located in Ruffini's corpuscles => responds to high temperatures

Cold Fibers: located in End-bulb of Krause. => activated in lower temperatures

27

A secondary consequence of activation of SNS is what?

 the stimulation of a1 receptors in the vascular smooth muscle (Vasoconstriction) leading to reduced heat loss.

28

If a neonate is lacking brown fat such as in prematurity, what could be a result?

Neonatal hypothermia

29

Describe how thyroid hormones effect heat

In Hyperthyrodism (Graves & Thyroid Tumor): Metabolic rate increased Heat Production increase

In Hypothyroidism (Thyroiditis, surgical removal of the thyroid, iodine deficiency) decreases metabolic rate and decreased heat production

30

Describe the difference in voluntary and involuntary response

involuntary=> hypothalamus stimulation, thyroid hormones, sweat glands, heat transfer by circulation

voluntary=> skeletal contractions

31

What are behavioral changes wrt voluntary heat production?

  1. Change is surface area
  2. Change in clothing
  3. Change in surroundings

32

describe temperature acclimatization

A person in a hot new environment has poor ability to perform work initially as core temperature increases and weakness may occur.

After several days there is a great improvement in work tolerance and much less increased core temperature

33

4. Hypothermia and Hyperthermia

hyperthermia: elevated body temperature due to failed thermoregulation that occurs when a body produces or absorbs more heat than it dissipates.

Hypothermia: a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as 35.0 °C (95.0 °F)

34

Define and describe Heat Exhaustion:

Bodies Response to increased temperature includes vasodilatation and sweating.

Excessive sweating, decreases ECF volume, decreased blood volume, decreased arterial pressure leading to Fainting.

35

Define and describe Heat Stroke:

 Body temperature increases to a point of tissue damage. Usually the normal response to elevated Temperature is impaired (i.e., sweating) core temperature increases to dangerous limits.

36

Define and describe Malignant Hyperthermia: 

37

During activities where it is hot and humid, How should a person combat this to avoid heat stroke?

increase intake of NaCl and fluid

38

What is Fever?

regulated rise in body temperature that is independent of ambient temperature

associated with increased thermopreferendum

39

What are the physiological differences between fever and hyperthermia?

Fever

  • regulated rise in body temperature
  • independent of ambient temperature
  • associated with increased thermopreferendum

 

Hyperthermia

  • impairment of thermoregulatory mechanisms
  • dependent on ambient temperature
  • decreased thermopreferendum

 

40

What are Some common pathogenic stimuli that induce fever?

  • exogenous pyrogens
  • Kupffer cell activation
  • Cytokine production
  • Complement cascade activation
  • Vagus nerve stimulation
  • PGE2 production

microbial and non-microbial agents can cause fever

41

What happens during an acute phase reaction?

Increases in temperature, slow wave sleep, acute phase proteins, neutrophils, pancreatic insulin, glucagon, SNS

Decreases in feeding

Pituitary hormones and behavior is altered

42

What are some benefits of fever?

  • enhace neutrol migration, phagocytosis
  • increase IFN production, antiviral/antitumor activities of IFN
  • Increase radical production, T cell proliferation, increase survival rate
  • reduced growth rate and viability of iron-dependent microbes

43

What is a routine anti-febrile therapy?

NSAIDs