Lecture 15: Temperature

Question 1

Thermal conformity (poikilothermy)

Answer 1

allow body temperatures to fluctuate with environmental temperature (exotherm)

Question 2

Thermoregulation (homeothermy)

Answer 2

• 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

Question 3

Regional homeothermy: core body temperature

Answer 3

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

Question 4

Regional homeothermy: Peripheral body temperature

Answer 4

• temperature of integument, limbs etc

- tends to vary considerably

Question 5

ectotherms or endotherms have broader temperature range tolerance

Answer 5

ectotherms

Question 6

metabolism vs. ambient temperature

Answer 6

higher metabolic rate the lower the ambient temp.

Question 7

acclimation and acclimatisation are

Answer 7

physiological changes in response to previous thermal history

Question 8

exposure to warm temperatures increases

Answer 8

heat tolerance, decreases cold tolerance

Question 9

thermal tolerance of many species changes with

Answer 9

seasonal changes in temperature.

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

Question 10

thermoregulation methods: behavioural control:

Answer 10

controlling body temperature by repositioning body in the environment

Question 11

thermoregulation methods: physiological control

Answer 11

• 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.

Question 12

endotherms respond to high ambient temperatures by

Answer 12

1) limiting heat gain

2) increasing heat dissipation

Question 13

In the thermoneutral zone body temperature remains

Answer 13

constant & no additional energy required

Question 14

Above the Upper critical temperature (above thermoneutral zone)

Answer 14

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

Question 15

Hyperthermia

Answer 15

• evaporative cooling cannot counteract heat gain

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

Question 16

problems with high temperature

Answer 16

• 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)

Question 17

how to limit heat gain:

Answer 17

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

Question 18

increasing heat dissipation:

Answer 18

Specific heat exchange surfaces

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

Question 19

whats allens rule

Answer 19

The warmer the climate the larger the size of appendages

Question 20

sweating:

Answer 20

Extrusion of water through sweat glands onto the skin

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

Question 21

panting:

Answer 21

Evaporative cooling through the respiratory system surfaces

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

Question 22

panting can cool ___ during high levels of activity

Answer 22

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

Question 23

rete mirabile

Answer 23

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

Question 24

endotherms respond to low ambient temperatures by

Answer 24

• increasing heat production (thermogenesis)

- limiting heat loss

Question 25

below the lower critical temperature:

Answer 25

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

Question 26

Hypothermia:

Answer 26

- increased metabolic production cannot compensate for heat loss - body temperature decreases (as does metabolism)

Question 27

problems with low temperatures

Answer 27

- 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

Question 28

Freezing:

Answer 28

- 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

Question 29

thermogenesis:

Answer 29

production of heat, esp in human / animal

Question 30

shivering: (thermogenesis)

Answer 30

- rapid contractions in groups of antagonistic muscles - no useful work generated - heat liberated by hydrolysis of ATP

Question 31

non-shivering thermogenesis:

Answer 31

- enzyme systems activated that oxidise fats to produce heat - virtually no ATP production

Question 32

3 forms of thermogenesis

Answer 32

- shivering - non shivering thermogenesis - heta absorbed by blood in vasculature and distributed throughout the body

Question 33

forms of body heat retention:

Answer 33

- insulation - aggregation - increased body size - circulation

Question 34

insulation:

Answer 34

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

Question 35

Aggregation

Answer 35

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

Question 36

increased body size benefit when cod:

Answer 36

- lower SA:V - generally thicker coats - Bergmanns rule

Question 37

Bergmanns rule

Answer 37

increase body size in cold climates, smaller in warm

Question 38

circulation:

Answer 38

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

Question 39

organisms which deal with subfreezing temperatures

Answer 39

- arctic woolly bear caterpillar - wood frog - snow fleas - painted turtle

Question 40

ice formation damage to organisms bodies

Answer 40

- cells shrink - membrane structure degrades - damage by ice crystals

Question 41

two strategies with dealing with subfreezing temperatures

Answer 41

- freeze avoidance,supercoiling (freezing point depression; use of antifreeze - freeze tolerance

Question 42

freeze avoidance/supercoiling

Answer 42

- 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

Question 43

freeze tolerance

Answer 43

ability to tolerate freezing of extracellular fluid - must be able to cope with... - -potential mechanical damage - -effects of dehydration

Question 44

what do Cryoprotectants do

Answer 44

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

Question 45

Antifreeze proteins:

Answer 45

Trehalose (2 glucose molecules)