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Animal Physiology > Regulation Of Body Temperature > Flashcards

Regulation Of Body Temperature Flashcards

0
Q

Ectotherm

A

An organism that regulates its body temperature by exchanging heat with its surroundings

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1
Q

Endotherm

A

An organism that generates heat to maintain its body temp at constant level

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2
Q

Temperature regulation and mitochondria surface area

A

Larger mitochondria surface area permits larger cytochrome oxidase activity to produce more ATP

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3
Q

Perfect ectotherm

A

Lizard

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4
Q

Perfect endotherm

A

Cat

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5
Q

Temporal heterothermy

A

Reducing metabolic rate by being at rest, allowing body temp to drop close to surrounding environment

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6
Q

Regional heterothermy

A

Maintain different temperature zones in the body

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7
Q

Core temperature

A

Temperature of internal organs, should remain at constant rate (37C)
Can fluctuate between 13-60Cat rest

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8
Q

Skin temperature

A

Changes with temp in the surrounding

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9
Q

Metabolic rate

A

Rate of energy expenditure (usually per hour)

Measured by calorie consumption (direct) or oxygen consumption (indirect)

4.8 ca, of best/L of oxygen

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10
Q

Basal metabolic rate

A

Rate of energy expenditure in a post absorptive condition (following a rest period)

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11
Q

Surface area : Volume ratio and BMR

A

Increase ratio = higher BMR

Lower ratio = low BMR

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12
Q

Factors affecting BMR

A 
Surface area to mass ratio
Age
Gender
Build 
Stress
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13
Q

Total metabolic rate

A

Total rate of energy expenditure during ongoing involuntary and voluntary activities

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14
Q

What affects total metabolic rate

A

Exercise
Hormones (thyroid, catecholamines, sex, growth)
Both increase TMR

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15
Q

Non shivering thermogenesis

A

Hormone mediated increase in TMR

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16
Q

Heat production

A

Heat is byproduct of metabolism
Hormones
Sympathetic activity
Muscle activity

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17
Q

Heat loss

A

Though the skin

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18
Q

Heat conductance

A

Ability to control amount of heat loss or gain between core and skin

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19
Q

Skin insulation

A

Blubber reduce best conductance via vasoconstriction.

Fur reduces heat conductance because it disrupts the heat gradient.

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20
Q

How does altering blood flow help thermoregulation?

A

Decrease external temp = vasoconstriction = reduce heat loss

Increase external temp = vasodilation = increase heat loss

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21
Q

Areas of highest heat conductance

A

Ears, face, hands

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22
Q

Heat loss by skin is affected by…

A

Radiation
Conductance (heat gradient)
Evaporation (breathing, sweating, increased via convection)

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23
Q

Why is sweating an important cooling mechanism?

A

Sweat is carried to surface of skin through duct

Sweat is isotonic to blood plasma excluding proteins

Most ions are reabsorbed

Keeps body cool because water is cool

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24
Q

Aldosterone and sweat

A

Reduces Na Cl excretion

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25
Q

Control of sweating

A

Cholinergic sympathetic pathway

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26
Q

Piloerector muscle

A

Surround hair follicles

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27
Q

Temperature regulatory center

A

Posterior hypothalamus

Receives negative feedback signals from sensory thermo receptors at skin that relay stimulus to anterior hypothalamus

28
Q

Thermo receptors

A

Cold pain
Cold
Warm
Hot pain

29
Q

Ratio of cold to hot receptors

A

10:1

30
Q

Adaptation of thermo receptors

A

Response of receptors fades gradually if exposed to same temperature continuously

31
Q

Spatial summation of thermo receptors

A

Thermal sensation is proportional to number of thermo receptors stimulated

32
Q

Hyoothalamus thermo receptors

A

Hot to cold = 3:1

33
Q

Set point

A

Determined by degree of activity of temp receptors in the hypothalamus.

Temperature deviating from set point elicit response

34
Q

How does skin temp affect set point

A

Increase skin temp = decrease set point
Decrease skin temp = increase set point (reduce heat loss)

Change in set point is to initiate thermo response sooner

35
Q

Specific response to heat

A

Inhibit thermo receptors in posterior hypothalamus

Sweating

Vasodilation

Decreased heat production

36
Q

Specific response to cold

A

Stimulate thermo receptors in posterior hypothalamus

Vasoconstriction

Piloerection (related to fur)

Shivering

Chemical thermogenesis

37
Q

Prolonged exposure to cold

A

Increase thyroid releasing hormone
Increase thyroid stimulating hormone
Increase secretion of thyroid
Increase metabolic rate

May enlarge thyroid gland

38
Q

Cold stimulate thermo center in posterior pituitary

A

True

39
Q

Heat stimulate thermo center in post pituitary

A

False

40
Q

Pyrexia

A

Fever

State of increased body temp beyond normal range due to infection or injury or cancer

Caused by response to pyrogens

41
Q

Most common pyrogens

A

Bacterial lipopolysaccharide toxin (LPS)

Viral polyribonucleotide pyrogen (poly I or C)

Cytokines from injured cells

42
Q

What receptors do pyrogens act on?

A

Toll receptors

Conserved cross species

43
Q

What do pyrogens activate?

A

Cyclo oxygenase 2 which produces prostaglandins

44
Q

Function of prostaglandins

A

Increase hypothalamic set point
Increase body temp

Inhibited by arachidonic acid like aspirin

45
Q

Hypothermia

A

Extreme cold causes decrease in body temp

46
Q

Extreme hypothermia

A

Can disrupt thermo system

Resist sleep to survive because you can enter comatose

Frost bites cause tissue damage by killing cells

Vasodilation causes momentary to permananent paralysis.

47
Q

Why is vasodilation important during extreme cold?

A

Blow flow to skin increase heat to prevent frost bite

48
Q

Why does the body raise set point due to infection?

A

Raising set point makes person feel colder so they shiver to generate heat rich raises their temp that is associate with a fever. This rise in body host is suppose to kill infections.

Increase neutrophil migration
Activate genes via heat shock
Survival is better when warm

49
Q

Why are fevers dangerous?

A

Can cause body to reach temp beyond critical range which can cause brain damage

50
Q

Hyperthermia

A

Extreme heat that causes body to reach upper temp limit due to insufficient cooling mechanisms

51
Q

Sustained hyperthermia results in…

A

Hemorrhage

Degeneration of cells

Damage to vital organs like liver, kidney, etc.

52
Q

How do mammals manage to sustain running while preventing heat stroke?

A

Anatomical adaptions

Counter current best exchange: carotid artery pass sinus with blood returning from nasal cavity. Close proximity cause exchange of heat. Cool blood moves to brain.

53
Q

Adaptations of marine mammals to extreme cold

A

Blubber increase insulation.

Counter current blood flow to extremities reduce heat loss.

54
Q

Adaptation of land mammals to extreme cold

A

Counter current heat exchange of blood moving to brain

Regional heterothermy

Low temp lipids

Fur

Heat shock enzymes make polyunsaturated lipids

55
Q

Temporal heterothermy: Dormancy

A

Deep sleep

Torpor

Hibernation

Allows body to drop to lower temp during times of non feeding to avoid energy lost

56
Q

Large animals and very small animals cannot hibernate, they exhibit deep sleep

A

True

57
Q

Marmots, ground squirrels, and some ectotherms hibernate

A

True

58
Q

Torpor

A

Short term change in body temp to help body survive in cold climate

Reduce core temp
Decreased metabolic rate
Decreased heart rate
Decrease breathing rate
Decrease O2 consumption
Blood supply restricted to vital organs
59
Q

Hibernation

A

Set point set really low

Maintain temp 1C above environment

Metabolism keeps temp above freezing

60
Q

Poikilotherm

A

Ectotherm

61
Q

Q10 effect

A

For every 10 degrees reaction rate doubles

62
Q

Biochem response in poikilotherms

A

Acclimatization increase O2 consumption

Heat shock change metabolic rate

63
Q

Freezing extracellular compartment

A

Poikilotherm survive cold by frees if their extracellular fluid compartment

Increases osmotic pressure in extracellular compartment which dehydrates cells

Increase intracellular concentration reduce freezing point so cells do not freeze.

64
Q

Super cooling

A

Prevent ice nucleating centres to prevent ice formation in cold temps

65
Q

Partial freeze tolerance

A

Produce cyroprotectants: trehalose and proline

Forms gel that stabilize cell membranes

Prevent formation of ice crystals

66
Q

Freeze avoidance

A

Produce antifreeze

Ie. glycoprotein prevent ice crystals from growing
Ie. sorbitol, glycerol increase osmotic pressure of fluid and decrease freezing point

67
Q

Behavioural and Physical mechanisms

A

Ex. Honey bees

Cold cause condensed swarming to reduce heat loss. Bees circulate from inside to outside of swarm to keep warm.

Heat cause loose swarm

Others: shivering, brown fat, circulation

Animal Physiology (5 decks)

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