Chapter 10 Flashcards
Metabolic rates
The resting metabolic rate varies with _____?
Thermoneutral zone?
- Bounded by lower and upper critical temps
- Within the TNZ, animals thermoregulate by controlling insulation
temperature
range of ambient temps where metabolic rate is independent of ambient temp
Insulation
Hair & feathers
- Can be compressed or erected
- Pilomotor responses are for _____?
- Ptilimotor responses are for ____?
- Erect hair/feathers traps a thick relatively motionless area of ____ , increasing the resistance to heat loss
- is what really insulates
mammals
birds
air
Insulation 2
Vasomotor responses
In cold, the sympathetic NS causes arteries leading to the skin to ____?
- Reduces heat loss
Postural responses
- Low temps
- Mammals curl up
- Birds tuck head under wing feathers or squat to enclose legs in feathers
vasoconstrict
Regional heterothermy
Appendages have lots of surface area for their sizes, while having less insulation
- Arms, legs, tails, ears
- Could account for significant heat loss
Animals and birds allow the appendages to ___, reducing heat loss
- Reduced temp gradient reduces heat loss
- May be ____ cooler than core portions of thorax, abdomen, and head
Appendages may also be used to remove excess heat
cool
10-35°C
Regional heterothermy 2
Countercurrent heat exchange
- Permits selective restriction of heat flow to appendages without altering oxygen supply, waste removal
Examples:
- Human arms
- Legs of many mammals and birds
- Flippers & flukes of whales
- Rodent tails
Often find 2 sets of veins, one deep and the other superficial
Temperatures below and above thermoneutrality
Below
- Heat production must ____
Above
- Increase active evaporative cooling
- examples???
Some mammals & most birds allow ____
increase
Sweating, panting, gular fluttering
hyperthermia
Shivering thermogenesis
Shivering – Universal in adult mammals & birds
- Unsynchronized, high-frequency contraction/relaxation of skeletal muscle motor units
- controlled by ____?
- No useful mechanical work produced
Somatic nervous system
Nonshivering Thermogenesis
- Very common in ____?
- Brown adipose tissue (BAT, brown fat)
- Found in 3 types of placental mammals ???
- Found in discrete regions
- Lots of blood vessels, and SNS neuronal fibers
- Cells contain great numbers of large mitochondria
placental mammals
- Cold-acclimated or winter acclimatized adults (especially of species with small to moderate body size)
- Hibernators
- Newborn individuals
Nonshivering Thermogenesis
Brown adipose tissue
- The SNS releases _____, binds to β–adrenergic receptors
- G-protein –coupled increase in ___
- cAMP phosphorylates (activates) intracellular ___
- Rate of stored lipid oxidation increases
- BAT is specialized for the uncoupling of oxidative phosphorylation
- Releases aerobic catabolism from normal controls
- Large amounts of lipids can be oxidized
- Releases aerobic catabolism from normal controls
- Causes chemical bond energy to be used for heat, instead of _____
- Uncoupling protein 1 (UCP1) is also called ____, not sure how it is upregulated
- UCP1 synthesis is increased if stimulation lasts longer than 10 min
- Fatty acid transport protein (FATP) may also be upregulated, allowing the cell to increase fatty acid uptake
norepinephrine
cAMP
lipase
ATP production
thermogenin
Hot environments: First Defense
Evaporation has a high price: it causes the loss of body water
- Therefore, it is a ___ line of defense
Behavioral defenses
- Desert rodents stay in burrows during the day and move outside at night
- Resting camels shift position to minimize surface area exposed to the sun
Insulatory defenses
- Some large diurnal mammals and birds native to hot areas have very thick fur/feathers
- Act as heat shields
Body temperature
- High amplitude cycling of body temperature and profound hyperthermia
last
Hot environments: First Defense 2
Cycling of body temperature
- Dromedary camels
- During the summer, a dehydrated camel let’s its deep body temp fall to 34-35°C overnight and then increase to 40+°C during the day
- Some stored heat is stored, and then lost using nonevaporative means
Hyperthermia
- High body temperatures help ____ heat gain
- Birds allow body temps to get as high as 44-45°C
- Antelopes such as the beisa oryz and Grant’s gazelle allow rectal temps to reach 45.5-46°C (114-116°F)
Keeping a cool brain
- _____ exchange allows warm arterial blood going to the brain to transfer heat to blood returning from nasal/upper respiratory passages
reduce
Countercurrent heat
Sweating
Saline is secreted by ___
Controlled by ____
examples?
Sweat glands missing from rodents, rabbits, hares
Pigs and dogs have sweat glands, but they do not produce enough sweat to play a role in thermoregulation
exocrine glands
sympathetic nervous system
Humans, horses, camels, some kangaroos
Panting
What is it?
Common in ___ and ___
Water evaporates from the warm, moist respiratory tract membranes
In some animals: Panting frequency increases with respiratory stress
In others: Panting frequency is generally constant (during panting)
- Dogs when cool: 10-40 breaths/min
- Dogs when stressed: 200+ bpm
Animals pant at resonant frequency
- Requires less muscular work
Increased breathing rate in response to heat stress
birds and mammals
Panting 2
Advantages over sweating
1.
2.
Disadvantages
1.
2.
- No salt loss
- Forcibly drives air saturated with water away from evaporative surfaces
- Loss of a given amount of water will require more energy
- May produce respiratory alkalosis
- Prevented by restriction of gas flow to upper airways
- Some species have evolved alkalosis tolerance
Gular fluttering
- Many birds
- Hold mouth open and rapidly vibrate floor of mouth cavity
- Increases airflow over vascular oral membranes
- Uses resonant frequency of involved structures
- No salt loss
- No alkalosis
- Requires less physical work than panting
Mammals & aves Acclimatize to winter & summer
Acclimatization of peak metabolic rate
- Allows the animal to thermoregulate in __ environments than before
- BAT
Acclimatization of ____
- Increase the length of time a high rate of metabolic heat production can be maintained
- Mechanisms unknown
Insulatory acclimatization
- Increased resistance to dry heat loss
- Metabolic rate required for thermoregulation is __
colder
metabolic endurance
reduced
Evolutionary changes
Arctic species have __ critical temperatures
- Broader TNZs
They increase metabolic rate ___ as temps drop
In hot climates, animals have ___ BMRs
lower
slower
lower
Hibernation & torpor
- Controlled hypothermia ?
- Hibernation – ?
- Estivation- ?
- Daily torpor –?
May be different manifestations of one process
Differ in duration and season
- letting body temp fall in a controlled manner
- temp drops close to ambient for several days during winter
- temp drops close to ambient for several days during summer
- temp drops close to ambient each day
Energy savings depend on _____?
ambient temperature
Hibernation & torpor 2
Winter sleep/carnivorean lethargy is?
ex?
Shallow form of hypothermia
Seen in some bears, racoons, skunks
Warm-bodied fish
Tunas, lamnid sharks, and billfishes have temperatures in certain regions that exceed water temperature
____ are warmed above water temp
- This is not enough as blood drainage greatly reduces temp
- Countercurrent heat exchange reduces heat loss
Billfishes have extrinsic eye muscles that no longer contract which are high in mitochondria – ATP-driven futile Ca2+ pumping. What does it do?
Red swimming muscles
Warms brain and retina
Insect endothermy & homeothermy
High metabolism of flight muscles may warm thorax
- The thorax is considered ___
Geometrid moths maintain temps 6° above ambient, but do not thermoregulate
- Still have thoracic endothermy
Other insects thermoregulate during flight
- Thoracic homeothermy
- Temporal or spatial
- Sphinx moths (Manduca sexta)
endothermic
