HO: 1-3 Flashcards
stimulus
change in the internal or external environment
receptor
cell which detects a change in the environment
modulator/control center
registers the change and initiates a response (sends information)
effector
structure or organ which causes the response
response
action taken in response to the stimulus
homeostasis
the maintenance of a stable internal environment in an organism, despite changes in the external environment
model used to describe homeostasis
stimulus-response negative feedback model
homeostasis involves
physiological systems, patterns of behaviour
physiological systems
rely on messages within the organisms body that can act on different parts of the body
patterns of behaviour
the whole organism does something to maintain homeostasis
negative feedback
response that reduces the intensity of the original stimulus
internal environment
refers to an organisms intracellular (cytosol), interstitial (tissue fluids) and intravascular fluids (fluids in veins)
external environment
conditions outside of the body cells (includes internal fluids and conditions outside the body)
internal factors kept within limits
pH, salt, water, sugar, temperature, wastes, O2, CO2
model
tool to help understand a system that can’t be seen
stimulus-response negative feedback model
stimulus - receptor - modulator/control center - response
why is the model negative?
it feeds back an opposite stimulus to the original
endotherm
an organism that can regulate its body temperature using metabolic processes, despite fluctuations in the environmental temperature. Eg. mammals and birds
thermogenesis
Metabolic mechanisms that generate heat
ectotherms
an organism that does not regulate its body temperature through metabolic processes - it fluctuates with the environmental temperature. Eg. reptiles and insects
heterotherm
animals that exhibit characteristics of both homeothermy and poikilothermy. Eg. bats
homeothermy
when homeotherms control their body temperature, making it relatively constant while the environmental temperature varies (activity is not dependent on environmental temperatures)
poikilothermy
poikilotherms present a body temperature similar to the environment. Their inner temperature varies as the environment temperature does (activity is dependent on environmental temperatures)
hibernation
long period of inactivity. Decrease in metabolic rate and body temp, reduces need for food and energy
torpor
daily periods of inactivity. Decrease in metabolic rate and body temp, reduces need for food and energy
Australian example of torpor
western pygmy possum. When below 12 degrees
Australian example of hibernation
short-beaked echidna
radiation in terms of heat transfer
thermal energy waves travel from the sun or from any object that is hotter and absorbed by the cooler object
conduction in terms of heat transfer
requires direct contact where heat energy is transferred from a hotter object to a cooler object
convection in terms of heat transfer
heat transfer via convection currents in air or water
Evaporation in terms of heat transfer
heat loss via water molecules turning into gas molecules
factors that affect amount of heat loss or gain
environment, SA/V ratio, temperature gradient and adaptations
methods of heat transfer
radiation, conduction, convection and evaporation
endotherms in cold environments are usually
large, round in shape and have small appendages
endotherm adaptations to reduce heat loss (cold environment)
fur, blubber, dark pigmentation on extremities, huddling, hibernation, vaso-constriction, blood shunting, counter-current exchange systems
endotherm adaptations to increase heat loss (hot environment)
shorter less dense fur, sweating, no fat, vaso-dilation, nocturnal, burrowing, thermal windows
thermal window
places with large SA/V ratio and less fur, to increase sweating for heat loss
ectotherm terrestrial adaptations
BSSNTPGR: basking/exposure, move to warm surfaces, move in and out of shade and burrows, activity (eg.nocturnal), torpor, change pigmentation, thermal gaping, body raising
vasodilation
when surface capillaries open wider, allowing more blood from the body core to flow to the body surface where increased heat loss occurs
vasoconstriction
when surface capillaries constrict, reducing blood flow from the body core to the body surface, reducing heat loss
circulatory shunt vessels
can direct blood flow to the surface vessels, or away from them, increasing or decreasing heat loss from the body surface
