Midterm 1 - Homeostasis/Thermoregulation Flashcards
Define homeostasis
Maintenance of a constant/normal internal environment
How is homeostasis achieved
coordinated responses of organs/systems that automatically compensate for environmental changes
examples of automatic compensation in homeostasis
body temp
blood pressure
O2/CO2 levels
what is coordinated response
more than 1 system - all systems working together
how does do systems automatically achieve homeostasis
automatically - involves autonomic nervous system (reflexes)
in terms of body temp, what are mammals and birds
homeotherms
what are homeotherms
warm-blooded animals
what do homeotherms maintain
body temp within narrow limits
can homeotherms tolerate high and low temp
no
how do birds function under higher heat
they have enzymes that are adapted
what does core body temp protect
vital organs
how is core body temp measured
rectal insertion of thermometer
what does core body temp get influenced by
environment
exercise
metabolism
what contributes to core body temp
vital organs and central nervous system
what is the thermoneutral zone
the ambient temp at which no adjustment is needed
when is no additional energy needed to maintain body temp
the thermoneutral zone - perfect husbandry conditions
what is needed during critical temperatures (hot or cold)
energy to maintain homeothermic condition
how is energy used to maintain homeothermic condition
produce or actively dissipate heat
basal metabolic rate
body does have to do anything to maintain core temp (same as thermoneutral zone)
hyperthermia
heat stress
what occurs in hyperthermia
cells are unable to function due to denatured proteins and enzymes - generally fatal
hypothermia
cold stress
what can survive freezing in hypothermia
cells
what can result in death due to hypothermia
blood circulation and respiration fail (blood can thicken)
how does heat mainly come in mammals and birds
body production (endothermic)
is endothermic heat production energy efficient
no
how is endothermic heat produced in mammals and birds
metabolism
growth and production
exercise
how does metabolism produce heat
conversion of nutrients to heat (energy)
where does heat metabolism mainly occur
heart
liver
kidneys
brain
what percentage of energy produced through exercise is heat
80%
what must happen to heat transported by blood
it must be released into the environment
what are the 4 physical processes for heat release
radiation
conduction
convection
evaporation/condensation
what is the best way to lose heat
evaporation/condensation (sweating/panting)
what are ways that extra heat can be produced
muscle activity (shivering)
non-shivering thermogenesis
what is shivering
rhythmic involuntary muscle contraction
what is the rhythm of shivering
15/sec
how do muscles contract during shivering
antagonistic muscles contract simultaneously
what does no exercise mean with energy
100% energy goes to heat production
what is the result of non-shivering thermogenesis
increased metabolism
how does non-shivering thermogenesis work
the sympathetic nervous system results in secretion of catecholamines which increases metabolism (calorigenic)
what most commonly increases metabolism during non-shivering thermogenesis
brown fat
what effect doe thyroid hormones have on metabolism
increases
which nervous system is the alarm system
sympathetic
what kind of animal is brown fat more prevalent in
young animals
how is extra heat lost under normal conditions
metabolic heat is removed from the core by the blood through the skin
what is the insulation property of the skin inversely proportional to
the blood flow
how does heat move in the body
through blood
what are gradient physical laws
transfer from high to low
radiation
electromagnetic radiation is emitted and absorbed
what is radiation relative to
the surface and temperature of the object/animal
what is conduction
transfer through contact
what does conduction depend on
the conductivity (inverse of insulation)
what is convection
transfer via moving air or water
what is the benefit of evaporation
very efficient
what does evaporation require energy for
to break water molecules apart
where does evaporation occur
through skin and airways
what is passive evaporation
normal water loss
what is sweating
active process under sympathetic nervous system
what does sweating result in besides heat loss
loss of ions
what is panting
rapid shallow breathing
what animals do no pant
horses
pigs
what is bathing
water absorb energy before evaporating
how do heat loss processes occur
usually simultaneously
what is important with heat loss
the type of animal (fur, size etc)
what kind of system is thermoregulation
automatic = reflex = sensor + integration + effectors
what nerve cells are involved in thermoregulation
thermoreceptors
what is the integration centre in thermoregulation
hypothalamus
what does is the hypothalamus involved with
information compared to internal reference set points
what are effectors in thermoregulation
neurons connected to muscles (somatic) for shivering
sympathetic nervous system for blood flow, sweat gland and metabolism
hormones - hypothalamopituitary axis
what is the voluntary component of thermoregulation
hypothalamus connected to the cortex = exchange of info
what does the voluntary component change
behavioural response -> putting jacket on (cognitive behaviour)
where are heat receptors found
in the skin below epidermis
in the body core
blood vessels
viscera
where in the body core are heat receptors especially found
hypothalamus
what is the hypothalamus’ sensitivity to temp
0.1 degree C
what is the anterior activation of the heat-loss centre
hypothalamus
what effectors slow down (experience vasodilatation)
sympathetic vasoconstriction fibers
how is information transferred when responding to heat
through warm sensory fibers
what does sensitivity to heat depend on
the animal and the external conditions (humidity level)
what animals have very good heat sensitivity
cattle
sheep
what animals have very bad heat sensitivity
pigs
why do pigs have such bad heat sensitivity
little sweat
small mouth forpanting
when is it preferred that pigs are transported due to their bad heat sensitivity
at night
what do birds have for heat sensitivity
air sacs
where are air sacs in birds located
they are an extension of the lung deep in body cavity
what is the purpose air sacs in birds
the ventilation helps cooling
where do most animals that aren’t good at regulating body temp reside
in the water - it mediated temp change
where are cold receptors located
in the skin below epidermis
in body core
where in the body core are cold receptors located
hypothalamus
blood vessels
viscera
how is cold response info transferred
through cold sensory fibers
are cold sensory fibers or warm sensory fibers more numerous
cold
how is the hypothalamus involved in cold response
through the activation of heat-producing centre
what is the adaptive mechanism to prolonged exposure to heat
lots of sweat
shedding
how does sweating occur during prolonged exposure to heat
increase in aldosterone stimulates reabsorption of Na+ and Cl- from sweat glands
what is the adaptive mechanism to cold
change of fur coat
increase in insulation properties (subcutaneous fat)
hibernation
what is hibernation
voluntary decrease in core body temp followed by a rapid raise
pathology involving thermoregulation
fever
hyperthermia
hypothermia
how does fever occur
by resetting hypothalamic thermostat to higher level
what is fever response equivalent to
a decrease in temp
what is fever caused by
pyrogens released during infection and tissue damage
when does hyperthermia occur
when temp exceeds regulating capability
heat production exceeds heat loss
what are consequences of hyperthermia
convulsions
nausea
loss of consciousness
death
how can one experience hyperthermia
excessive exercise
exposure to high temperatures
when does hypothermia occur
when heal loss exceeds heat production capability
what are consequences of hypothermia
slow nervous activity
muscular failure - cardiac, pulmonary
death
what is hypothermia critical with
newborns
is fever technically good or bad
good
