hormones and feeding behaviour Flashcards
motivation
behaviour in pursuit of a goal
fundamental element of our interaction with the world and with each other
motivation to obtain basic needs
food, water, sex and social interaction
regulation of motivated behaviours is achieved by the coordinated action of… which act within…
a) molecules
b) peptides
c) hormones
d) neurotransmitters
specific circuits that integrate multiple signals for complex decisions to be made
2 main reasons why we eat
- to meet the needs of the STRUCTURAL parts of the body (muscles, bones)
- to obtain ENERGY to fuel the body
energy balance
FOOD INTAKE to maintain HOMEOSTASIS
mammalian brain depends on GLUCOSE as main energy source
what in the adult brain have the highest energy demand?
neurons
they require CONTINUOUS delivery of glucose from blood
brain accounts for what percentage of body weight and consumes how much glucose-derived energy?
2% of body weight
consumes 20% of glucose-derived energy
what in the body is the main consumer of glucose?
the brain
2 primary systems that regulate food intake
- homeostatic
- hedonic
homeostatic regulation of food intake
controls energy balance by…
increasing motivation to eat following DEPLETION OF ENERGY stores
hedonic regulation of food intake
increases desire to consume foods that are HIGHLY PALATABLE
two time scales of energy balance
- short-term energy balance
- long-term energy balance
short term energy balance
acts primarily as determinant of satiety
to limit size of individual meals
long term energy balance
acts to keep body mass within a relatively fixed range
over weeks, moths, years
food intake is divorced from…
homeostatic processes
it relies on NON-HOMEOSTATIC processes like:
a) experience
b) habits
c) availability
ie. if rats receive a meal consistently at time 0, will begin to show ANTICIPATORY endocrine responses 1-2 hours in advance of the learned mealtime
fasting and refeeding
animals fluctuate between a well-fed and fasting state
correlated changes occur in secretion of:
a) hormones
b) neurotransmitters
c) neuromodulators
prandial state
after consuming a meal
- blood is full of NUTRIENTS
- energy is stored in 2 forms:
a) GLYCOGEN
b) TRIGLYCERIDES - glycogen reserves: liver and skeletal muscles
- triglyceride reserves: adipose (fat) tissues
what kinds of nutrients are absorbed from a meal?
- glucose
- fatty acids
- triglycerides
- glycogen
anabolism
occurs after eating a meal
during the prandial state
process by which proteins are formed from amino acids
post-absorptive state
fasting condition
- glycogen and triglycerides are BROKEN to be used as fuel
catabolism
catabolism
during post-absorptive state
glycogen and triglycerides are broken down (catabolized) into smaller molecules that can be used as fuel by the cells of the body
the feeding system is in proper balance when…
energy reserves are replenished at the SAME AVERAGE RATE that they are expended
when does obesity occur?
simplified answer:
if intake and storage of energy consistently exceeds the usage
then amount of body fat increases
eventually results in obesity
when does starvation occur?
simplified answer:
if intake of energy consistently fails to meet body’s demands
loss of fat tissue occurs
eventually results in starvation
well-fed versus fasting animals: have HIGH BLOOD CONCENTRATIONS of…
well-fed:
a) glucose
b) amino acids
c) insulin
d) leptin
fasting:
a) glucagon
b) glucocorticoids
well-fed versus fasting animals: HIGH STORES of…
well-fed:
a) body fat in adipose tissues
b) glycogen in liver
fasting:
a) free fatty acids
well-fed versus fasting animals: which have high LIPOGENIC (FAT-SYNTHESIZING) ENZYMES?
well-fed animals
fasting animals have high:
a) lipolytic enzymes
b) ketone bodies
c) circulating ghrelin
well-fed versus fasting animals: other hormones/neuropeptides they’re high in
well-fed:
a) CCK
b) alpha-MSH
c) CART
fasting:
a) NPY
b) MCH
c) orexin
d) corticotropin-releasing factor
e) catecholamines (NE and EP)
orexigenic hormone/compound
an appetite stimulant
a) increases appetite
b) may induce hyperphagia
hyperphagia
medical term for an extreme, insatiable hunger
anorexigenic hormone/compound
reduces appetite
results in lower food consumption
examples of orexigenic molecules
NPY
MCH
orexin
noradrenaline
examples of anorexigenic molecules
alpha-MSH
CRH
TRH
CART
ocytocin
serotonin
2 phases of energy utilization and storage after a meal
- postprandial phase
- postabsorptive phase
posprandial phase
first phase of energy utilization/storage after a meal
a) the fed state
b) embodies the digestion and absorption of nutrients
c) 6-12 hours
postabsorptive phase
second phase of energy utilization/storage after a meal
a) once the nutrients are digested, absorbed and utilized
b) they’re stored in designated tissues
when do the posprandial and postabsorptive phases occur?
postprandial:
a) immediately after food ingestion
postabsorptive:
a) insulin secretion has to have risen, while glucagon secretion has fallen
basic overview of well-fed state
- good is broken down into glucose, free fatty acids, amino acids. glucose powers brain and muscles
- insulin is released from pancreas to facilitate the transport of glucose
- excess glucose is converted to glycogen and stored in liver and muscles
basic overview of fasting state
- glucagon is released from pancreas
- glycogenolysis breaks down stored glycogen in liver
- lipolysis in adipose tissue releases free fatty acids and glycerol
- liberated glucose and ketone bodies power the brain
what powers the brain in the well-fed versus fasting states?
well fed = glucose
fasting = liberated glucose and ketone bodies
5 points on insulin
- liver: conversion of glucose to glycogen
- glycogen is stored in liver and muscle
- insulin facilitates transport of glucose into muscle and fat cells
- and transport of amino acids into muscle cells - liver: amino acids are converted into ketone bodies
- in peripheral cells: insulin is needed for glucose oxidation and lipogenesis, processes that result in storage of fat in adipose tissue
what does the liver do to glucose?
converts it into glycogen
some of this glycogen = stored in liver, some in muscle
what does liver do to amino acids?
converts them into ketone bodies
what is insulin needed for in peripheral cells?
for glucose oxidation and lipogenesis
these processes result in storage of fat in adipose tissue
hormones other than insulin that are involved in metabolism during the well-fed state
epinephrine, norepinephrine, glucocorticoids, thyroid hormones, growth hormone, somatomedin, glucagon
two phases of insulin release
- cephalic phase
- gastrointestinal phase
cephalic phase of insulin release
release of insulin from pancreatic cells occurs as result of SENSORY STIMULI associated with FOOD INTAKE
even before nutrients are present
ie. arrive at home and smell your fav dinner - even before your first bite, body starts to release insulin
gastrointestinal phase of insulin release
primary storage of excess nutrients taken in during meal occurs in this phase
when insulin is released in response to absorption of nutrients from gut
metabolism during the fasting state: 5 points
- energy reserves are mobilized from storage to meet energy needs
- metabolic system is designed to provide sufficient levels of energy to brain
- after fasting, ketones are formed, and these can also be used by brain when glucose is scarce
- glucagon release, gluconeogenesis, and sympathetic stimulation of fat breakdown are the most common mechanisms for raising blood sugar levels without eating
- during fasting state, cells in periphery switch from metabolizing glucose for ATP production to metabolising free fatty acids mobilized from the lipids stored in adipose tissue
what are formed after fasting, and they can be used by what?
ketones
can be used by brain when glucose is scarce
fasting state: most common mechanism for raising blood sugar levels without eating
glucagon release
gluconeogenesis
sympathetic stimulation of fat breakdown
during fasting state, cells in periphery switch from…
metabolizing glucose for ATP production
to metabolizing free fatty acids mobilized from lipids stored in adipose tissue
metabolic system is designed to provide sufficient…
levels of energy to the brain
glycogenolysis, lipolysis and gluconeogenesis are all part of…
part of fasting state
glycogenolysis
breakdown of stored glycogen in the liver or muscles
to provide a steady supply of glucose for energy
