Thermoregulatory System Flashcards
what is homeostasis?
maintaining of internal environment as response to external stimulus
what’s temperature homeostasis?
body detects changes and then responds to correct them to a set point by mechanism called negative feedback
what’s an endothermic animal?
maintain constant body temp independently of their environment
what are the temps for a human, dog, pig and chicken?
human - 36.1-37.2
dog - 37.9 - 39.9
pig - 38.7 - 39.8
chicken - 40.6 - 43.0
where is the thermoregulatory system?
hypothalamus
what detects the changes in temperature?
thermoreceptors in the brain and the skin
what are the two centres involved with temperatures?
heat gain centre - when animals get too cold
heat loss centre - when animals get too hot
what happens when temperatures change?
- change in temp stimulates thermoreceptors which trigger action potentials to relay information via sensory neurone to hypothalamus
- hypothalamus sends information via motor neurons to the effectors (skin)
- a response occurs such as sweating and vasodilation of arterioles to allow heat to escape from skin if body too hot
responses to high temperature
vasodilation - arterioles dilate which allows more blood to enter the capillaries
pilorelaxation - pilli erector muscles relax which lowers the hairs and feathers on the skin so that air can circulate, allows for convection and evaporation.
sweating - glands secrete heat onto skin where it evaporates and takes heat from the body. adrenal and thyroid glands secrete adrenaline and thyroxine which reduces metabolic rate and heat generation
gular fluttering - increases heat loss through the mouth it occurs in birds when they rapidly flap membranes in throat for evaporation
panting - process of evaporation of water through nasal passages, mouth, lungs, and birds air sacs.
behavioural changes - stretching out body gives larger s.a for heat loss or seeking of shade.
responses to a low temperature
vasoconstriction - arterioles constrict so less blood flow to the skin
piloerection - pils erector muscles contract causing hairs or feathers on skin to raise to trap an insulated layer reducing heat transfer from the skin. moulting can also help
shivering - muscles contract and relax rapidly and cause heat to be produced by friction and respiration
brown adipose tissue - cells take lipids and run them through the mitochondria to generate heat. it is present in almost all mammals.
behavioural changes - curling up causes a smaller surface area for the heat to escape. animals may move to warmer areas and show increased movement
metabolic rate in animals
endothermic - can adjust their metabolic rate to regulate their internal body temperature. metabolic reactions give off heat so animals can alter their internal temperature by changing their metabolic rate
ectothermic - cannot use this mechanism on their environment
countercurrent mechanism
heat is exchanged between two sources flowing in opposite directions. in heat regulation the flowing sources are the blood stream, when body temp drops the arteries carry warm blood away from the heart while veins take deoxygenated into the heart. as these two pass the warm arteriole blood transfers most of its heat to the cool venous blood and body temp is balanced
extremes of temperature
hypothermia - body cannot maintain normal body temperature changes, there are three phases (symptoms dependent)
- mild, weaknesses, shivering, lack of alertness
- moderate, muscle stiffness, low BP, slow breathing
- severe, fixed or dilated pupils, inaudible heartbeat, difficulty breathing, coma
hyperthermia - the elevation of the body temp above the normal. fever hyperthermia results from inflammation within the body. non fever results from all other causes of increased body temperature. symptoms are panting, dehydration, reddening of the gums, decrease in urination, uncoordinated movements and unconsciousness can also cause organ dysfunction and death.
physiological adaptations
adaptations in an animals body processes e.g., snakes are physiologically adapted to produce venom which they use in defence against predators
anatomical adaptations
adaptations in an animals shape and structure e.g., bat forelimb has become adapted to form wings, improving their access to suitable food sources
behavioural adaptations
adaptations in an animals language, tool use and survival strategies, e.g., migration, in some bird species to avoid harsh environments
evolution definition
a change in characteristics over several generations
specification definition
the formation of a new species as part of the evolutionary process
variation
differences between organisms, it can include variations in diet, behaviour and aesthetics. variation between animals is linked to differences or changes in the DNA because of this variations are passed down to offspring
natural selection
some variations give an animal an advantage over other animals, e.g., being able to run for longer, reach higher branches or have better camouflage. animals with advantageous variation are more likely to survive and are more likely to reproduce as variation is heritable.
speciation
over time it can lead to evolution of a species. if animals in a species develop different variations which both give them advantages it could lead to the species separating into 2 species
adaptions of a polar bear
large feet with fur on the soles improves the grip on the ice
small s.a to vol ratio and small ears to reduce heat loss
strong legs help catching their prey when swimming and running
thick layer of adipose under the skin for insulation and energy
sharp teeth and claws for feeding and defending
pregnant females hibernate
highly developed sense of smell and hearing
different types of selection pressures that affect variation
stabilising - reduces variation. between animals Dna. extreme phenotypes are reduced and proportion of animals with average phenotype is increased
directional - encourages a particular new phenotype usually in response to environmental changes
diversifying - increases variation between animals DNA, extreme phenotypes become more common and average phenotypes are reduced
