Temperature 3 Flashcards
what are the two types of ‘special’ endothermy (2)
- temporal endothermy
- regional endothermy
temporal endothermy
- changes in body temperatures over time
regional endothermy
- body temperature varies in regions of the body
temporal endothermy: example
- hibernating animals
regional endothermy: examples (2)
- billfish use heater organs near eyes
- tunas and sharks retain heat in red muscle
what is the purpose of localized warming of skeletal muscle (2)
- used for sustained locomotion
- leads to faster contraction frequencies and more forceful contractions
white muscle function
- used for bursts of locomotion used every so often
red muscle function
- used for sustained locomotion
where is the red muscle located in fish without regional endothermy and what are the implications (2)
-red muscle located externally along the body wall
- leads to muscle being cooled by external passing water
where is red muscle located in fish with regional endothermy and what are the implications (2)
- red muscle is internalized and insulated by white muscle
- heat is better controlled and protected from heat loss by passing water
what contributes to the elevated red muscle endothermy of tuna an sharks (2)
- heat produced in the muscle is retained there due to internalization and insulation
- rete mirabile
rete mirabile (2)
- extensive countercurrent arrangement of arterioles and venules
- transmits heat from venous to arterial blood to retain heat
in the rete mirabile arrangement, which vessels get warmed/cooled (2)
- the venous blood is cooled by incoming arterial blood
- the arterial blood is warmed by exiting venous blood
what do we know about tuna red muscle that alludes to their ability to practice regional endothermy
- red muscle is always warmer than ambient temperature
what do we know about tuna red muscle that alludes to their ability to actively regulate their temperature (2)
- red muscle warms faster than it cools
- if rates were the same, the muscle would simply be a conductor
what determines the control of temperature and rate of muscle warming/cooling in tune
- the rete mirabile system
how might warm muscles affect oxygen unloading in humans (2)
- right shift of the OEC, stabilization of the T state and increase in P50
- would result in enhanced O2 unloading in humans
how might warm muscles affect oxygen unloading in fish (2)
- fish Hb are not temperature sensitive, so it has no effect
- may be beneficial to protect the fish from excessive O2 unloading
what cells are the heater tissue of billfish eyes composed of
- modified, non-contractile muscle cells
what is the mechanism used to create heat in heater tissue cells (3)
- T-tubule activates Ca2+ release from sarcoplasmic reticulum into cytoplasm
- stimulates ATP-consuming metabolic processes
- mitochondria produce more ATP
what mechanism is used to retain heat in the heater organ
- carotid rete system (countercurrent exchange) localizes heat to eyes and brain
how does cranial temperature change during dives in billfish
- cranial change stays relatively constant even though water temperature drops
why do billfish have a heater organs near their eye/brain (2)
- allows them to see better (higher Q10)
- makes them better predators, especially against pray at lower depths where it is colder
what terms are used to describe the thermal zones/limits in homeotherms (3)
- thermoneutral zone
- upper critical temperature (UCT)
- lower critical temperature (LCT)
homeotherms: thermoneutral zone (2)
- range of temperature optimal for physiological processes
- metabolic rate is minimal in this range
homeotherms: upper critical temperature (2)
- metabolic rate increases as animal induces a physiological response to prevent overheating
- upper limit of the thermoneutral zone
homeotherms: lower critical temperature (2)
- metabolic rate increases to increase heat production
- lower limit of the thermoneutral zone
homeotherms: what occurs outside of the LCT (2)
- metabolic rate increases for thermogenesis
- onset of hypothermia occurs when animal can no longer maintain homeostasis of body temperature
homeotherms: what occurs outside of the UCT (2)
- metabolic rate increases for active cooling
- onset of hyperthermia occurs when animal can no longer maintain homeostasis of body temperature
what terms are used to describe the thermal zones/limits in poikilotherms (3)
- preferred temperature
- incipient lethal temperature
- range of tolerance
poikilotherms: preferred temperature
- ambient temperature for optimal physiological function
poikilotherms: incipient lethal temperature (2)
- ambient temperature at which 50% of animals die
- animals have an incipient upper lethal temperature (IULT) and an incipient lower lethal temperature (ILLT)
poikilotherms: range of tolerance
- range of ambient temperatures between the IULT and the ILLT
what terms describe the thermal tolerance of animals (2)
- eurytherm
- stenotherm
eurytherm
- can tolerate a wide range of ambient temperatures
stenotherm
- can tolerate only a narrow range of ambient temperatures
eurytherms vs stenotherms: thermal niches
- eurytherms can occupy a greater number of thermal niches than stenotherms
thermal tolerance: aerobic scope (3)
- represents the energy available for any activity above resting
- changes depending on the temperature
- aerobic scope = maximal metabolic rate - resting metabolic rate
thermal tolerance: Topt
- temperature where the maximum aerobic scope occurs
thermal tolerance: Tcrit
- temperature where there is no aerobic scope (animal is dead at these temperatures)
what holds membrane lipids together
- Van der Waal’s forces
how are membranes affected by temperature
- membrane fluidity is affected by temperature
membrane fluidity: low temperatures
- membrane lipids solidify, decreasing membrane fluidity
membrane fluidity: high temperatures
- increase memebrane fluidity
what do changes in membrane fluidity affect (2)
- affect protein movement
- increased membrane fluidity results in increased protein movement
how do membrane fluidities change in animals living in different temperatures with different body temperatures
- membrane fluidity is maintained relatively constant across animals at their respective body temperatures
what term is used to describe how animals can maintain membrane fluidity at different temperatures
- homeoviscious adaptation
homeoviscous adaptation
- maintain membrane fluidity at different temperatures by changing composition of membrane lipids
what is the mechanisms of homeoviscous adaptation (4)
- fatty acid chain length
- saturation
- phospholipid classes
- cholesterol content
homeoviscous adaptation: fatty acid chain length
- shorter chains increase fluidity because of reduced interactions with neighbouring fatty acids
homeoviscous adaptation: saturation
- more double bonds (unsaturation) increase fluidity due to their introduction of kinks into the tail of the phospholipids
homeoviscous adaptation: phospholipid classes (3)
- phosphatidylcholine (PC): decrease fluidity
- phosphatidyethanlamine (PE): increase fluidity
- involves change in the phospholipid head group
homeoviscous adaptation: cholesterol content
- higher cholesterol content prevents solidifying when membrane is cooled
membrane remodeling (2)
- used to achieve homeoviscous adaptation
- describes the rapid modulation of membrane fluidity by decreasing saturation in existing phospholipids, or by synthesizing new phospholipids and inserting them into the membrane while taking unwanted phospholipids out
