Exam 3: Homeostasis : Hunger Flashcards
food supplies __ and __ needed for…
food supplies energy and nutrients needed for growth, maintenance, and repair of the body
nutrients stored in 2 types of reservoirs
short-term store and long-term store
glucose
principal sugar used for energy
especially in brain
Glycogen
complex carbohydrate made of glucose molecules
sored for short-term in liver and muscles
Glycogenesis
conversion of glucose to glycogen
regulated by pancreatic hormone, insulin
Glycogenolysis
conversion of glycogen to glucose
controlled by glucagon
Parts of short-term energy reservoir
glucose, glycogen, glycogenesis, glycogenolysis
lipids
fats for long-term storage
deposited in adipose tissue
Gluconeogenesis
if food deprivation prolonged, this occurs
converts fats and proteins to glucose and ketones (form of fuel)
what does the brain prefer, glucose or ketones?
glucose
parts of long-term energy reservoir
lipids and gluconeogenesis
fasting phase vs absorptive phase
fasting: when digestive tract empty
absorptive: when tract is full
Intermittent fasting example
wait to not eat for hours on end to be able to pull from the long-term reservoir (prolonged food deprovation)
what does gut-brain axis control?
hunger and feeding behaviors
glucoprivation
drop in blood glucose levels
triggers hunger
information from glucodetectors in liver and mechanosensory receptors in stomach travel via ___ to the ____
vagus nerve
nucleus of the solitary tract (NST) in brainstem
nucleus of the solitary tract (NST)
receives and integrates appetite signals from many sources
- important in feeding behaviors
gastric distension detected by…
stomach
gut brain axis informs brain of …
glucose levels
efferent fibers to the pancreas modulate insulin release
hypothalamus
coordinates many systems to regulate hunger and feeding
dual center mode of appetite control(2)
lateral hypothalamus and ventral hypothalamus
lateral hypothalamus
promotes hunger
ventral hypothalamus
regulates satiety
lesions and excitability to lateral hypothalamus
lesion: animals stop eating
excitability: induced eating
lesions and excitabaility in ventral hypothalamus
lesions: overeating
stimulation: suppressed eating
where is the paraventricular nucleus (PVN)
ventral hypothalamus
VMH
sexual behavior in females AND hunger and feeding role
arcuate nucleus
contains an appetite controller governed by several hormones
all peptides from gut and fat arrive here and modulate eating depending on if they are anorexigenic or orexigenic
arcuate nucleus
2 sets of neurons the arcuate system relies on
POMC neurons
NPY neurons
POMC neurons
inhibit appetite and raise metabolism promoting weight loss
- does not release POMC
what do POMC neurons release into the lateral hypothalamus ?
alpha melanocyte-stimulating hormone
NPY neurons
stimulate appetite directly and inhibit POMC neurons
NPY neurons 2 functions
- release NPY
- project to the PVN of ventromedial hypothalamus
what are brainstem regions involved in when the pathway goes NPY to PVN
involved in autonomic nervous system functions
what are brain regions involved in that go in pathway through POMC to lateral hypothalamus
involved in food seeking behavior
ghrelin
released from GI system when digestive system is empty
what does ghrelin bind to to stimulate eating behaviors
binds to receptors on NPY neurons in hypothalamus
when are ghrelin levels a their highest?
when fasting
get sharp drop after eating
what nervous system does ghrelin activate?
ANS - parasympathetic (rest and digest)
ghrelin turns NPY on and what happens to the PVN?
it is turned off
ghrelin goes from NPY neuron to POMC neuron turning POMC off so it cannot release alpha msh to lateral hypothalamus, what happens to the orexin neuron?
it is disinhibited and turned on
orexin
peptide produced in the LH (lateral hypothalamus) that also increases feeding
projections from arcuate go to 2 main areas, what are they?
orexigenic neurons and anorexigenic neurons
orexigenic neurons
of lateral hypothalamus acts to increase appetite and food intake
anorexigenic neurons
of paraventricular neurons act to decrease appetite and feeding
where do orexin neuron axons project to?
brain regions involved in motivation and movement
- neocortex, PAG, RF, thalamus, and LC and spinal cord
where do anorexigenic neurons project to?
brainstem regions (including NST) which regulates ANS function
cholecystokinin (CCK)
intestines control rate of stomach emptying through release of CCK
- directly suppresses eating by inhibiting the vagus
- peptide released in response to the presence of fats
Peptide YY3-36
released by small intestine after meal, proportional to calories ingested
- works in opposition to ghrelin
lots of calories = lots of PYY released
CCK and PYY both signal
satiety
long-term satiety signals from…
adipose tissue
long-term satiety signal discovered in obese mouse ob/ob
fat cells are unable to produce hormone leptin
anti-obesity hormone
increases metabolism decreases eating
- leads to false under recording of body fat composition
