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Endo > Thermoregulation > Flashcards

Thermoregulation Flashcards

1
Q

Define thermoregulation

A

The ability of an organism to maintain a relatively constant body temperature despite fluctuations in external environmental temperature

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2
Q

Define endotherm

A

Heat geenrated by heat production from body

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3
Q

Define homeotherm

A

Temperature maintained within narrow limits

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4
Q

Define ectotherm

A

Heat from external sources

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5
Q

Define poikilotherm

A

Body temperature across wide range of environmemtal temperatures i.e. lots of variation in temperature dependig on environment

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6
Q

Define thermoneutral zone

A
  • The range of temperatures where basal metabolic rate is enough to maitnain the body temperatuer within normal limits
  • either side will increase metabolic rate to maintain body in normal range
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7
Q

What components are within the thermoregulatory system?

A
  • Sensory component
  • Integrating component
  • Motor component
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8
Q

Describe the sensory component of the thermoregulatory system

A

Neurons with nerve endings that have thermoreceptors continuously monitor body temperature and transmit to the integrating centre

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9
Q

Describe the integrating centre in the thermoregulatory system

A
  • Hypothalamus
  • Compares temperature information with internal reference or set point
  • Like a thermostat
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10
Q

Describe the motor component in the thermoregulatory centre

A
  • Neurons that send command signals to alter heat production or loss
  • Move animal to warmer/cooler area or stimulate shivering
  • Travel via somatic motor system and affect heat production in skeletal muscles
  • Or sympathetic system to chenge
  • Physiological and behavioural changes
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11
Q

What changes can be made by the thermoregulatory signals travelling in sympathetic nerve fibres?

A
  • Alter blood flow to skin
  • Activity of sweat glands
  • Activity of smooth muscles that regualte thickness of fur or plumage
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12
Q

What is the function of the anterior hypothalamus in thermoregulation?

A

Cooling centre (cools body)

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13
Q

What is the function of the posterior hypothalamus in thermoregulation?

A

Heating cente (warms the body)

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14
Q

Outline the thermoregulatory pathway in cold

A
  • Skin thermoreceptors detect reduction in temperature, sent to cerebral cortex and hypothalamic thermostat
  • Cooled blood reaches hypothalamus
  • Information from cerebral cortex to the hypothlamus
  • Cerbral cortex causes voluntary responses e.g moving from cold to warm place
  • Hypothalamus stimulates SNS stimulation, TRH release and shivering
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15
Q

What is the effect of TRH release from hypothalamus?

A
  • To anterior pituitary
  • Stimulates TSH release
  • To thyroid
  • Stimualtes T4/T3 release
  • Increased basal metbaolic rate leading to heating
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16
Q

What are the effects of SNS stimulation?

A
  • Piloerection
  • Stimualtes adrenal medulla, release of adrenaline and noradrenaline
  • Adrenaline increases BMR
  • Noradrenaline leads to skin vasoconstriciton
  • SNS stimulates brown adipose tissue thermogenesis
17
Q

Outline the thermoregulatory pathway in heat

A
  • Skin thermoreceptors detect increase, signal to cerebral cortex and hypothalamic thermostat
  • Warmer blood to hypothalamus
  • Cerebral cortex sends to (and receives signals from) hypothalamus
  • Cerebral cortex stimulates voluntary responses e.g. move somewhere cooler
  • Hypothalamus causes adrenergic inhibition and stimulates cholinergic nervous system
18
Q

What are the effects of adrenergic inhibition?

A
  • Decreased BMR

- Skin vasodilation

19
Q

What is the effect of cholinergic stimulation in thermoreguation?

A

Sweating

20
Q

What is the functionof the thermoregulatory feedback mechanism?

A
  • Allows clsoe regulation of body temperature

- I.e. if cools self too farm sends signal to stop and increase heat production

21
Q

What causes the fever response?

A
  • Exposure to pyrogens

- Increase hypothalamic set point - New “normal” set for body to be regulate to

22
Q

What are pyrogens?

A

products from bacteria or cytokines from inflammation etc that stimulate an animal to have a fever

23
Q

What is the function of fever?

A
  • Defence mechanism
  • Improved T-cell and immune function
  • May limit invading organsism growth (body can cope but pathogen cannot)
  • HOWEVER some invading organsims may evolve to adapt and benefit from fever
24
Q

What is brown adipose tissue?

A
  • Specialised adipose tissue found in most mammals, particularly neonates
  • In large mammals may still be present in adulthood
  • In rodents can be switched on and off throughout life
  • Switched on upon arousal in hibernating mammals
25
Q

Where is brown adipose tissue commonly found?

A
  • Perirenal
  • Interscapular
  • Abdominal
26
Q

Describe the structure of brown adipose tissue compared to white adipose tissue

A
  • Small cells with central nucleus
  • Multilocular TAG droplets, greater SA for lipid metabolism (only 1 or 2 in white)
  • Abundant mitochondria richly endowed with respiratory chain enzymes, spread throughout cell (in white are fewer and pushed to side)
  • Higher degree of vascularisation
27
Q

How does brown adipose tissue generate heat?

A
  • Uses uncoupling protein 1 (UCP1)
  • Eists in inner mitochondrial memrbane
  • Uncouples mitochondrial energy production to generate heat (in normal tissues, mitochondria gerenate with minimial heat loss)
28
Q

Compare normal and uncoupled cellular respiration

A
  • Electron transport chain pumps H+ into intermembrane space of mitochondria
  • Creates concentration gradient
  • In coupled: H+ pass through ATP-synthase, with each passage producing one ATP molecule
  • In uncoupled: H+ pass throguh UCP1, generating heat as flood through
29
Q

What are the stimulatory factors for UCP1 activity in BAT?

A
  • Most switched on at birth
  • Cortisol
  • Sympathetic NS
  • Cold temeprature
  • Leptin
  • Prolactin
  • Thyroid hormones
30
Q

What factors make neonates more susceptible to cold than adults?

A
  • Higher ratio of body surface to body volume
  • Higher proportional surface area of head (significant heat loss)
  • Lack of musculature and inability/reluctance to shiver
  • Poor thermal insulationdue to lack of subcut fat, also wet
  • Inability to move away from cool areas
31
Q

What is meant by altricial?

A
  • Immobile
  • Lack of hair/down
  • Closed eyes (not all)
  • Immature HPA axis at birth
32
Q

What is meant by precocial?

A
  • Mobile after birth
  • Hair/down present
  • Eyes open
  • Mature HPA axis at birth
33
Q

What is the function of melanophores in amphibian and lizard thermoregulation?

A
  • Contain dark melanin pigment
  • Makes skin darker
  • Able to absorb more solar radiation in order to increase temperature
34
Q

What are some cardiovascular adaptations fo birds for shedding or conserving heat?

A
  • No sweat glands, lose heat via blood shunts
  • Dilate large vascular plexus on back of neck
  • Large proportion of blood from left ventricle to legs to increase heat loss during stress
35
Q

Why is it important for reptiles to be maintained in the preferred optimal temperature zone?

A
  • Affects metabolism

- Digestion is temperature dependent

36
Q

Why should reptiles be starved 1 week before hibernation?

A
  • Digestion is temperature dependent
  • A temperature drop is what triggers hibernation
  • If enter hibernation before all food has been digested, will rot and lead to death
37
Q

What are some respiratory mechanisms of the bird used for thermoregulation?

A
  • Panting
  • Gular fluttering
  • Air sacs
  • Panting and gular fluttering for evaporative heat loss
38
Q

Outline some thermoregulatory measures of rodents

A
  • Shivering
  • Huddling together
  • lots of born fat
  • Peripheral vasoconstriction/dilation of ears and tail
  • Tunnel underground (cooler/warmer depending on environment)
  • Stretching out to increase heat loss
  • Seek shade
  • Evaporative heat loss via saliva

Endo (30 decks)

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