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APS 136 animal physiology, reproduction & development > Lecture 15: Temperature > Flashcards

Lecture 15: Temperature Flashcards

1
Q

Thermal conformity (poikilothermy)

A

allow body temperatures to fluctuate with environmental temperature (exotherm)

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2
Q

Thermoregulation (homeothermy)

A
  • maintain body temperature at relatively constant levels largest independent of mean environmental temperature
  • Generate most body heat physiologically
  • regulate body temperature (Tb) by adjusting heat protection
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3
Q

Regional homeothermy: core body temperature

A
  • temperature at the interior of the body (thoracic and abdominal cavity, brain, etc)
  • maintained within narrow margins
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4
Q

Regional homeothermy: Peripheral body temperature

A
  • temperature of integument, limbs etc

- tends to vary considerably

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5
Q

ectotherms or endotherms have broader temperature range tolerance

A

ectotherms

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6
Q

metabolism vs. ambient temperature

A

higher metabolic rate the lower the ambient temp.

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7
Q

acclimation and acclimatisation are

A

physiological changes in response to previous thermal history

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8
Q

exposure to warm temperatures increases

A

heat tolerance, decreases cold tolerance

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9
Q

thermal tolerance of many species changes with

A

seasonal changes in temperature.

Due to: Changes in enzyme systems & changes in membrane phospholipids

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10
Q

thermoregulation methods: behavioural control:

A

controlling body temperature by repositioning body in the environment

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11
Q

thermoregulation methods: physiological control

A
  • neural responses (immediate)
    • e.g. modification of blood flow to skin, sweating/panting, shivering etc.
  • Acclimatisation responses (long-term)
  • -changes in insulation or capacity to metabolically produce heat etc.
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12
Q

endotherms respond to high ambient temperatures by

A

1) limiting heat gain

2) increasing heat dissipation

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13
Q

In the thermoneutral zone body temperature remains

A

constant & no additional energy required

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14
Q

Above the Upper critical temperature (above thermoneutral zone)

A
  • zone of active heat dissipation
  • -animal increases activity to increase heat loss
  • –evaporative cooling
  • Hyperthermia
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15
Q

Hyperthermia

A
  • evaporative cooling cannot counteract heat gain

- body temperature (As does metabolism) towards upper lethal T

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16
Q

problems with high temperature

A
  • denaturisation of proteins
  • -structural and enzymatic
  • inadequate O2 supply to meet metabolic demands
  • different temperatures effects on interdependent metabolic reactions (“reaction uncoupling”)
  • membrane structure alterations
  • increased evaporate water loss (terrestrial animals)
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17
Q

how to limit heat gain:

A

Increased size :

  • Large animals have large heat capacities and low SA:V
  • -take longer to heat up
  • Large animals tend to have thicker pelage
  • -insulate body from external heating
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18
Q

increasing heat dissipation:

A

Specific heat exchange surfaces

  • Enable heat loss through conduction/convenction/radiation
  • thin cuticle
  • highly vascularised
  • lightly insulated
  • large surface areas
  • Allens rules
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19
Q

whats allens rule

A

The warmer the climate the larger the size of appendages

20
Q

sweating:

A

Extrusion of water through sweat glands onto the skin

  • passive (little energy expenditure)
  • high salt loss
  • no convection
  • no effect on blood pH
21
Q

panting:

A

Evaporative cooling through the respiratory system surfaces

  • active (requires muscle contraction)
  • no salt loss
  • convection -increases cooling
  • increased ventilation leading to increased pH
22
Q

panting can cool ___ during high levels of activity

A

brain.
- Rete mirabile
- maintain brain temperature despite abnormally high body temperature

23
Q

rete mirabile

A

heat exchange between warm arteriole blood and cooled venous blood from nasal cavity

24
Q

endotherms respond to low ambient temperatures by

A
  • increasing heat production (thermogenesis)

- limiting heat loss

25
Q

below the lower critical temperature:

A
  • Zone of metabolic regulation
  • -increase in metabolism to increase heat production to balance increased heat loss
  • shivering, BAT etc.
  • Hypothermia
26
Q

Hypothermia:

A
  • increased metabolic production cannot compensate for heat loss
  • body temperature decreases (as does metabolism)
27
Q

problems with low temperatures

A
  • thermal inactivation of enzyme faster than rates of activation
  • inadequate O2 supply to meet metabolic demands
  • different temperature effects on interdependent metabolic reactions (“reaction uncoupling”)
  • membrane structure alterations
  • freezing
28
Q

Freezing:

A
  • drastic reduction in gas function
  • -liquid water vs. solid water
  • drastic reduction in enzyme function
  • -reduces molecular mobility
  • structural disruption of enzymes
  • mechanical disruption of cell membranes
  • osmotic dehydration due to freezing of extracellular water
  • -most important factor
29
Q

thermogenesis:

A

production of heat, esp in human / animal

30
Q

shivering: (thermogenesis)

A
  • rapid contractions in groups of antagonistic muscles
  • no useful work generated
  • heat liberated by hydrolysis of ATP
31
Q

non-shivering thermogenesis:

A
  • enzyme systems activated that oxidise fats to produce heat
  • virtually no ATP production
32
Q

3 forms of thermogenesis

A
  • shivering
  • non shivering thermogenesis
  • heta absorbed by blood in vasculature and distributed throughout the body
33
Q

forms of body heat retention:

A
  • insulation
  • aggregation
  • increased body size
  • circulation
34
Q

insulation:

A
  • fur/hair.feathers (pelage)
  • -reduce effects of convection
  • Fat/blubber
  • -lower thermal conductivity of integument
  • low metabolic activity (low perfusion needed)
35
Q

Aggregation

A

-reduce convection effects (cluster together i.e.penguins)

36
Q

increased body size benefit when cod:

A
  • lower SA:V
  • generally thicker coats
  • Bergmanns rule
37
Q

Bergmanns rule

A

increase body size in cold climates, smaller in warm

38
Q

circulation:

A
  • reduced asking perfusion
  • -limit heat loss from blood
  • countercurrent exchange
  • -heat transferred from arteries to veins
  • -limit heat loss from extremities
39
Q

organisms which deal with subfreezing temperatures

A
  • arctic woolly bear caterpillar
  • wood frog
  • snow fleas
  • painted turtle
40
Q

ice formation damage to organisms bodies

A
  • cells shrink
  • membrane structure degrades
  • damage by ice crystals
41
Q

two strategies with dealing with subfreezing temperatures

A
  • freeze avoidance,supercoiling (freezing point depression; use of antifreeze
  • freeze tolerance
42
Q

freeze avoidance/supercoiling

A
  • water usually freezes below 0 degrees celsius
  • supercoiing can be enhanced by addition of solutes to an aqueous solution
  • -in conc of solutes, decrease freezing point
  • -e.g. insects:
    1) produce high levels of glycerol
    2) low freezing point
    3) willow gall fly larvae can supercool to -60 degrees C
43
Q

freeze tolerance

A

ability to tolerate freezing of extracellular fluid

  • must be able to cope with…
  • -potential mechanical damage
  • -effects of dehydration
44
Q

what do Cryoprotectants do

A

reduce ice crystal formation e.g. glucose, ethylene glycol.

45
Q

Antifreeze proteins:

A

Trehalose (2 glucose molecules)

APS 136 animal physiology, reproduction & development (17 decks)

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