Lecture 15 - body temp Flashcards
where is heat prod in the body
most heat prod is by liver, heart, brain, kidneys and endocrine organs,
inactive skeletal muscle muscles contribute 20-30% of body heat
body temp, a balance
balance bn heat prod and heat loss
vigouorus excerise = heat prod by skeletal msucles
thrfr = change in physical activity is a key way to change body temp
average 37, fluctuates in the day
low AM, high PM
for every 1 deg inc, rate of reactions inc by 10%
if too high = proteins are denatured nad neurons depressed
convulsions = seizure warning at 41
limit for life = 43
cooling is tolerated better, esp for heart surgery
core and shell temp
core = organs w/in skull, thoracic and abdominal cavities
shell = skin, limbs
core has highest temp, shell = the lowest
how is body temp reg, shell vs core
blood = major heat transfer agent bn core and shell
if shell is warmer = heat is lost
if heat needs to be conserved = blood bypasses the skin = slows down loss
shell temp fluctuate (20-40deg)
core remains constant
mechanism of heat exchange
list them, no info
**heat always flows down its thermal gradient
radiation
conduction
convention
evaporation
radiation
loss of heat by in dared waves
about 50% of body heat is lost this way
eg. cold room warming up once filled with people
body soaking up heat from sun
- movement of heat from warmer to colder by waves
conduction
transfer of heat bn objects in direct contact with one another
needs molec to molec contact bn objects.
thermal E must move through a material medium
ex. standing up after sitting down and the seat being warm
convection
warm air rises and is replaced by cool air lower down
cool air absorbs heat faster than warm air
AC/fan = speeding up the rate you’re unloading heat from the body
evaporation
water molecs. absorb heat (have enough E to escape as a gas = heat of evaporation
insensible water/heat loss = continuous evaporation of water from lungs, mouth, skin, not aware of it, can’t change/measure it.
sensible heat loss = sweating = active process that you’re aware off
1. under extreme emotional states
2. while doing vigorous excerise
role of hypothalamus
major integrating centre for thermoreg.
2 thermoreg centres.
= heat loss centre
= heat promoting centre
peripeheral + centreal thermoreceptors send input to hypothalausm
hypo = initiates proper loss/promoting reflex mechanism
info from central receptors is more imp
heat promoting mechanism
vasoconstriction
shivering
inc in MR
enhanced thyroxine release
behavioural modification
vasoconstricition
sympathetic vasoconstrictor
blood is restricted to deep body areas
core temp main tend, shell drops
ok for short, too long = frost bite = cells die
shivering
when vasoconstriction is not enough
stretch receptors in some muscles = involuntary shivering
muscle activity = gen heat loss
inc in MR
cold stimulates release of NE by SNS, inc MR = more heat prod
esp in infants w more brown adipose tissue (w more mitochondria)
since babies can’t shiver right away, so BAT is the only thing they have
enhanced thyroxine release
as fall goes to winter,
hypothalamus of kids release more TRH, stim more release of TSH, results in more TH (t3 and t4)
inc MT + body heat as by product
inc ability to maintain constant body temp as env cools
behavioural mods
warmer clothing
ingesting warm fluids
inc physical activity
shrink on our selves (posture)
heat loss mechanism
most through the skin
when body temp increases
- heat promoting centre = ing
- heat loss = activated
vasodilation of cutaneous blood vessels
sweating
behavioural mods
vasodilation of cutaneous blood vessels
turn off sympathetic vasoconstriction
heat loss by radiation, conduction, convenction
sweating
if overheated, vasodilation is not enough
sweating is activated by SNS
good if dry, not so effective if humid
behavioural mods
looking for shade, cooling, less actiity
light coloured loose fitting clothes
hyperthermia
heat stroke
when heat loss process become ineffective
core body temp reaches 41
inc body temp depresses hypothamaus = stops heat control mechanims
horrible positive feedback
inc temp, inc MR, inc heat prod
if keeps rising = skin becomes dry, organs can become damaged, possible heat stroke.
