Thermogenic hormones Flashcards
Thermoregulation
process where the body regulates temperature
ideal temperature in humans
37C
ways body generates heat
deep organs like liver, brain, heart, GI system, and skeletal muscles
where is the heat lost in the body
the skin
rate of heat loss depends on
body composition
environmental temperature
body composition with more fat is good for
good insulator and prevents heat loss
what is the max heat the body absorb
50C
how is internal and external temperature detected
specialized neurons throughout the body
skin
which receptors are more present
cold receptors (10x)
where can temperature receptors be other than the skin
deep in organs detecting internal temperature
where do the receptors send their action potentials
hypothalamus
how does the hypothalamus regulate body temp
peripheral vasoconstriction
peripheral vasodilation
shivering
brown adipose tissue
metabolic rate
sweating
thermoregulation is active or passive
both
passive heat transfer
radiation: infrared radiations are emitted from the skin
conduction: heats surrounding air, object, water
convection: body heats up air that is taken away by a breeze
active heat loss
evaporation: panting, sweating
thermogenesis
production of heat
passive in body: heat is released by other activities
how can heat be produced passively
control of the chemical reaction rate of cells
digestion of food
exercise
active heat production
shivering thermogenesis
non-shivering thermogenesis
shivering thermogenesis
cold environment or illness, SNS causes muscles to tremor
cold receptors trigger this shivering response and prevents sweating by sending signals to the hypothalamus
non-shivering thermogenesis
SNS and hormones like catecholamine, epinephrine, norepinephrine, T4 T3 and others increase metabolic rate of body and produce heat
what specializes in non-shivering thermogenesis
brown adipose tisue
t/f the amount of heat made by BAT is not significant for overall body heat
true
why is BAT considered an endocrine gland
primarily responds to hormones
structure of BAT
derived from mesenchymal stem cells
how does BAT generate heat
express a protein called UCP-1
energy uncoupling
uncoupling protein UCP-1
enzyme
uncouples mitochondrial ATP energy production
how does the UCP-1 generate heat
allows protons to pass the membrane of the mitochondria without interacting with the normal ATP-generating protein
does BAT use a lot of energy
yes
requires it to pump protons out of the mitochondria
how does BAT get energy
fat droplets within the brown adipose cells
can also get fat and glucose from extracellular fluid (blood plasma)
neural control of BAT
involves the SNS
cold receptors send signals to the brain
neural stimuli from ANS
increase energy consumption and uncoupling of mitochondria in BAT
production of heat and secretion of other hormone-peptides
how does BAT power the proton gradient
uses FFA and glucose
discoveries about BAT
women have more than men
older people have less
??
how much body fat does BAT consume in a year
4kg
where is BAT located in healthy people
supraclavicular and around scapula
orexin
neurotransmitter-hormone produced in brain neurons
regulates arousal, wakefulness and appetite
promotes differentiation of BAT cells and mesenchymal stem cells
required for non-shivering thermogenesis
incretin
increases the amount of insulin released by beta islet cells of the pancreas
stimulates receptors in the hypothalamus
promotes BAT thermogenesis
DIT hormone
increase non-shivering thermogenesis
mechanism unknown
T3 T4
increase size number and efficiency of mitochondria = higher basal metabolic rate and heat generation
what happens to TSH in chronic cold temperatures
is elevated and can lead to goiters
norepinephrine
interaccts with beta3 adrenergic receptors causing activation of hormone sensitive lipase
turns fat into FFA used by BAT
increases overall body metabolism of glucose by promoting glycogenolysis
increases uncoupling and heat generation
cold pressor test
CV test that is done by immersing an individual’s hand in ide water and measuring the changes in BP and HR
what is a pressor
substance that causes vasoconstriction
to what are the CV responses of the CPT due
norepinephrine effects
