Lecture 10 Flashcards
What is the metabolic hormone
Thyroid hormone T3 and T4
What is another name for a parafollicular cell
C cell
What is another name for a C cell
parafollicular cell
What is the function of calcitonin
Lowers blood calcium
What produces calcitonin
C cells/parafollicular cells
What do parafollicular cells produce
Calcitonin
What is calcitonin secreted in response to
Increase of blood levels of calcium
What stage of life is calcitonin the most important
Childhood for the skeleton
What is the definition of the MR
body’s rate of energy expenditure per hour = total heat
What are the two ways BMR can be measured
Direct - water
Indirect - see how much oxygen you consume
Name for “energy cost of living”
BMR
what unit is BMR reported as
kcal/m^2/hr
Which sex is BMR higher in
males; more skeletal muscle
What is the major determining factor of BMR
Body surface area
Why is body surface area the major BMR determining factor
You need to maintain heat, higher surface area, quicker you lose heat
BMR is ______ proportional to age
inversely
How can stress increase metabolic rate
epi increases metabolic rate by increasing fat catabolism; heat generates
_______ and BMR are tightly associated
Body temp
What is the most important hormonal
factor in regulating BMR
Thyroid hormong
(metabolic hormone)
High MR; poor heat tolerance; weight loss
Hyperthyroidism
(too much heat, too much MR, therefore you lose weight)
Low MR; obesity, poor cold tolerance
Hypothyroidism
(not generating enough heat, not enough MR, too cold)
What is TMR
total metabolic rate
What is the sum of BMR and voluntary activities
TMR
what is food induced thermogensis
eat food
energy needed to digest
rapid increase in TMR
does fasting/low caloric intake increase or decrease MR
decrease
Heat produced by skeletal muscle can be ______ times that of rest of body
30-40
what is the average body temp
37 degrees celcius
For every 1 degree rise in temp, rate of catalytic reactions increases by ____
10%
What happens if your body temp is too high
Proteins start to get denatured
What temp is the limit for life
43 degrees
what temp do convulsions in adults begin
41 degrees
is an increase or decrease in body temp tolerated better
decrease
Loss of heat by infrared waves
Radiation
Radiation
Loss of heat by infrared waves
What percent of body heat loss is by radiation
50%
What kind of heat exchange?
movement of heat via waves
Radiation
What kind of heat exchange?
Direct physical contact; through a material medium
Conduction
Give an example of radiation
cool room warming when filled with people
What kind of heat exchange?
Warm air rises, cold air sinks
Cool air absorbs heat, rises and process repeats
Convection
Forced convection
Convection enhanced by wind or fan (forces air across body)
Heat of vaporization
Water molecules absorb enough heat to escape as gas
Insensible water loss
basal heat loss due to continuous evaporation from lungs
Insensible heat loss
Heat loss we cannot regulate/control
What percent of basal heat production is insensible
10
When does evaporation become a sensible heat loss
when body temps rise
Where are the thermoregulatory centers found
Hypothalamus
What are the two thermoregulatory centers
Heat loss
Heat promoting
Where are peripheral thermoreceptors
The shell
Where are central thermoreceptors
In the core - sensitive to blood temp
what does the hypothalamus receive afferent input from
peripheral and central thermoreceptors
The input from what thermoreceptor is most important
central
lowering of shell temp can alert hypothalamus to do what
preserve core temp
Name the 4 heat promoting mechanisms
vasoconstriction of skin BV
Shivering
Increase metabolic rate
Release more thyroxine
Increase in MR is also known as
chemical/nonshivering thermogenesis
what kind of fat in adults can generate heat by burning triglycerides and glucose
brown fat
What two heat conserving mechanisms is not seen in adults
Increase in MR
Increase thyroxine release
Why is shivering so effective
muscle activity generates a lot of heat
Most heat loss mechanisms occur through the ______
skin
Name the 3 main heat loss mechanisms
Vasodilation of skin BV
Enhanced sweating
Behaviour modifications
Sweat glands are strongly activated by which NS
sympathetic
When does hyperthermia occur
when normal heat loss procedures are ineffective
Hyperthermia is an example of a _______ feedback cycle
Positive
Explain the positive feedback cyc;e with hyperthermia
Temp increases
as a result, MR increases
as a result, temp increases
as a result, MR increases
etc
what is coined as controlled hyperthermia
fever
what releases pyrogens
macrophages
macrophages release what in regards to temp
pyrogens
What do pyrogens do
cause a reset of hypothalamic thermoregulatory centers
What kind of molecule is a pyrogen
cytokine signaling
the majority of energy output is in the form of ____
heat
define hunger
a physiological need to eat
appetite
desire for specific types of foods
satiety
satisfatction of hunger
not hungry
What two nuclei are key centers in appetite regulation
arcuate nucleus
solitary nucleus
where is the
solitary nucleus
in the brain stem
where would you find the VMN and LHA neurons
Hypothalmus
What is the role of the VMN nerons
tell us that we had enough to eat
What is the role of the LHA neurons
tell us when were hungry
What does the VMN release to signal satiety
CRH
(corticotropin releasing hormone)
What does the LHA neurons to release to stimulate hunger
orexins
POMC/CART neurons release what, and work on what
melanocortin
VMN neurons
What is the long name of VMN
ventromedial nucleus
What is the long name for LHA
lateral hypothalamic area
What stimulates the LHA
release of neuropeptide Y and agouti-related peptide
(NPY/AGRP)
What does ARC stand for
arcuate nucleus
The LHA is to hunger as the _____ is to satiety
VMN
What group of neurons in the ARC stimulates satiety
VMN
What group of neurons in the ARC stimulate hunger
LHA
What is the most important short term hunger hormone
Insulin - satiety signal
Does protein make you feel fuller for longer or shorter
Longer
What released from stomach is a potent hunger stimulator
Ghrelin
Where is ghrelin released from
Stomach
When do glucagon levels rise
During fasting
What does cholecystokinin do for appetite
Depresses hunger
Does increased body temp increase or depress hunger
depress
higher body temp, higher MR, probably due to eating
What is leptin
a peptide hormone
What releases leptin
adipose tissue
What does leptin inhibit and increase
Inhibits NPY secretion
Increases CART expression
More adipose tissue = more _____
Leptin
Does leptin increase or supress appetie
Supresses, so you use up the adipose tissue stored
