Feeding Flashcards
Why do we eat and drink?
To fuel our body- nutrients to perform functions
eating and drinking
internal and external (sensory) experiences drive feeding behaviors to restore balance
Do I need the food?
Homeostasis (balance)- thirst, hunger
glucose levels, proteins, fats, salts, water
Do I want the food?
Incentive motivation
flavors, reward, hedonic tone
homeostasis
maintaining “set point”
homeostasis monitors physiological mechanisms
blood glucose, body fat, salt levels, etc.
compare to “set point”
more water, more food/bigger meal if more expended
if deficient, stimulate seeking/feeding
a little hungry after you come home from class
hungry after a swim practice
extremely hungry/starving if you get lost while hiking
if surplus, suppress seeking/feeding
negative feedback regulation
had a big lunch, not as hungry when dinnertime comes
redundancies
multiple mechanisms of maintaining homeostasis
in case one system fails, another one can help pick up slack
endotherms
generate our own heat through metabolism and muscles
body temperature tracked on face
trigeminal nerve- controls movement in face and sensory - received information about temperature of face- is important because is close to brain and brain is important
internal body core
collecting info and sending it to the brain
brain receives information about the entire body- if cold or hot
most important brain region in controlling temperature
pre optic area/ thalamus
if we are cold
stimulate (shiver, reduce blood flow, increase metabolism)
reduce sweat, suppress the increase in blood flow, suppress the increase in respiration
can also change behavior
redundancies- makes it more complicated!
why do we drink water?
loses a lot of water a day
urination, feces, sweating, evaporate water
osmolality
number of particles (salts) per unit volume of water
isotonic salt solution
0.9% NaCl
0.9 grams NaCl in 100 milliliters water
hypertonic
more salty than an isotonic solution
hypotonic
less salty than an isotonic solution
What is a 0.5% NaCl solution?
A. Hypertonic
B. Hypotonic
C. Isotonic
B. hypotonic
how does water move in/out of cells?
intracellular/extracellular
osmosis
intracellular compartment
within cells
extracellular compartment
outside of cell (includes fluid between cells and blood plasma)
osmotic thirst
high salt concentration in extracellular compartment
regular water loss (respiration, perspiration, urine)
eat something salty
water flows out of cells
more common kind of thirst
osmosensory neurons in hypothalamus (OVLT)
cells shrink based on water content (like a shriveled balloon)
ion channels open-> EPSP
action potential -> triggers osmotic thirst response
vasopressin release
OVLT->
preoptic area-> hypothalamic thirst network-> drinking
OR
preoptic area-> supraoptic nucleus, paraventricular nucleus-> water conservation
vasopressin
reduces urination- conserves water that you have
hypovolemic thirst
too little volume of extracellular fluid
large water loss (vomiting, hemorrhage, diarrhea)
lose water AND salts so no change in osmolarity/concentration of salt
blood pressure drops causing
baroreceptors (detect pressure changes in blood vessels/heart) signal to brain via autonomic nervous system
baroreceptors (detect pressure changes in kidney) cause renin-> angiotensin 2 release into the blood
pre-optic area (like osmotic thirst)- different pathways to preoptic area
hypovolemic thirst->
blood pressure drops-> cardiac baroreceptors detect-> vagus nerve-> brain-> preoptic area
AND
kidney baroreceptors detect pressure change-> renin-> angiotensin 2 -> subformical organ-> preoptic area
angiotensin 2 release triggers
hypovolemic thirst (drink water and eat salty food) via circumventricular organ- saline IV. or Gatorate
reduces urination, increases blood pressure
circumventricular organ/formical organ
structure that senses angiotensin 2 and activates the preoptic area
What monitors hypovolemic thirst?
A. Hormones in the blood
B. Baroreceptors in blood vessels
C. Neurons in the hypothalamus
B. baroreceptors in blood vessels
why do we stop feeling thirsty (satiety)?
combination of factors:
mouth and throat are wet
water in stomach, but extracellular compartment not replenished
estimate of how much we have consumed
food allows for energy storage
short-term storage as glycogen in muscles and liver requires insulin
long-term storage as adipose tissue
what causes us to feel hungry vs sated?
insulin? NO!
blood glucose levels? NO!
multiple hypothalamic systems
insulin
low blood insulin leads to hunger
high blood insulin also leads to hunger since it causes hypoglycemia
blood glucose levels
people with untreated diabetes have high blood sugar levels, but are hungry
hypothalamic systems for eating regulation
ventromedial hypothalamus (VMH)
lateral hypothalamus (LH)
ventromedual hypothalamus (VMH)
damages leads to hyperphagia, then new set point
“satiety center”
lateral hypothalamus (LH)
damaged leads to aphagia, then new set point
“hunger center”
hyperphagia
eating more- damaged VMH= eating excessively
aphagia
eating less- damaged LH=eating close to nothing
body warns hypothalamus about nutrient surplus/deficiency
leptin, insulin, ghrelin, PYY (3-36)
leptin
released by fat cells into blood, allow for monitoring of body energy reserves
insulin
released by pancreas into blood, allow for monitoring of blood glucose levels
ghrelin
released by stomach into blood while fasting, appetite stimulant
PYY (3-36)
released by intestine into blood while ingesting food, appetite suppressant
hypothalamic circuits for feeding
feeding hormones travel to 2 sets of neurons (POMC and NPY neurons) in arcuate nucleus of the hypothalamus -> neurons either decrease or increase appetite
NPY cells
ghrelin activates - do need to eat- has opposite effect compared to other 3
leptin, insulin, PYY 3-36 inhibits - don’t need to eat
POMC neuron
leptin activates- signals to not eat- not directly
only chemical that effects POMC
anorexigenic neurons
of the paraventricular nucleus (PVN) decrease appetite and feeding
orexigenic neurons
of the lateral hypothalamus (LH) increase appetite and food intake
CLASS QUESTION
Which of these hormones is released rapidly during/after a meal?
A. Ghrelin
B. PYY 3-36
C. Leptin
D. Insulin
B. PYY 3-36
