Mod 4. L31 Flashcards
stressors
stimuli that disrupt an organism’s homeostatic state, requiring adjustment or adaptation
these will lead to the organism experiencing stress
animal responses to stressors
avoidance/escape
resistance
tolerance
susceptibility
Endocrine-disrupting chemicals EDC
anthropogenic compounds that can affect the synthesis, reception, and degradation of various endogenous hormones
EDCs can mimic the effects of sex steroid hormones and affect the sex ratios of TSD species
autonomic control (heat regulation)
- vertebrate animals can alter the blood flow to their skin, which affects the temperature gradient
- activation of piloerector muscles increases the extent of fluffing of pelage and plumage, increasing the effectiveness of insulation by increasing the amount of trapped unstirred air
- sweating and salivation during panting can cause evaporative cooling
vasodilation
arterioles vasodilate or vasoconstrict in response to signals from the nervous system
when dilated = more blood flow to the capillaries (closer to skin), greater heat transfer
when constricted = less blood flow = less heat loss
Tunica media
the smooth muscle around arteriole
its contraction and relaxation allow for the diameter of the arteriole to change
norepinephrine (and vasoconstriction)
binding to alpha-adrenergic receptors on smooth muscles around arterioles causes muscle contractions (vasoconstriction)
epinephrine (and vasodilation)
binding to beta-adrenergic receptors causes smooth muscles to relax (vasodilation)
acetylcholine ACh (and vasodilation)
binding to muscarinic ACh receptors to cause smooth muscles in the tunica media to relax (vasodilation)
thermal neutral zone (TNZ)
in a resting homeothermic endotherm, it is the range of ambient temperatures where metabolic rates remain near the basal metabolic rate )Ie the ambient temperatures at which body temperature remains constant without resorting to a change in metabolic rate)
Upper critical temperature (UCT) and Lower critical temperature (LCT)
indicate temperatures above and below which metabolism increases over basal level to maintain Tb (body temperature)
passive processes for thermoregulation
(activated in TNZ thermal neutral zone)
vasodilation / vasoconstriction
piloerection , fluffing up of plumage
active processes for thermoregulation
sweating
panting
shivering thermogenesis
non-shivering thermogenesis
shivering thermogenesis
heat is produced by the contraction of antagonistic muscles such that there is little net movement of muscles
non-shivering thermogenesis
stored fat is oxidized through respiration that is uncoupled from ATP synthesis and all energy is dissipated as heat
protons bypass ATP synthase and go through the UCP channel, when protons go through it heat is generated but not ATP.
brown adipose tissue
poikilotherms
very sensitive to changes in ambient temperatures
pejus temperature
in pokilotherms, at a certain point, the maximum metabolic rate starts to decrease (as temperature increases) as physiological systems deteriorate or fail to meet metabolic needs. this temperature is called pejus temperature
above Tp organisms cannot perform at maximum capacity
why does the Maximum metabolic rate decrease after Tp (pejus temperature)
as temperature increases you get changes in the efficiency of oxidative phosphorylation.
it decreases after the Tp because the mitochondria cannot operate efficiently anymore to generate ATP
passed Tp the membranes start getting leaky and protons bypass the ATP synthase and leak back into mitochondria elsewhere, not creating ATP
due to the gradient that it forms it further produces heat
proton leak
allows protons to move across the mitochondrial membrane via pathways other than the ATP synthase
so oxygen utilization and movement of protons without ATP synthesis
critical temperature (Tc)
the organism only has sufficient energy to survive
at or above Tc, one can also observe a shift to anaerobic metabolism, as oxygen demand exceeds supply (Tc in fishes)
there is a higher and lower Tc
