Food intake Flashcards
Why is correct regulation of food intake important? (3)
-Energy (food) is essential to fuel our bodies
- Low energy availability causes changes in response to other stimuli
-Excess or insufficient energy can contribute to disease
–Obesity
–Anorexia-cachexia
What are the internal + external cues that may regulate energy homeostasis? (10)
internal:
-Food
-taste
-social habits
-environment
- Looking/foraging for food
external:
- hormones
-growth from the muscle
- signals from WAT/liver, pancreas (bidirectionally connected to the brain)
- gut-brain microbiome axis
-metabolism
-neuroendocrine communication
the brain exerts a top down influence on external + internal cue. What does this mean?
The brain is overseeing the integration of information from a variety of external = internal cues .
What are the 2 primary drivers of food intake? (2)
homeostatic vs hedonistic feeding
Define homeostasis
The tendency towards a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes
Define Hedonism
The pursuit of pleasure; sensual self-indulgence
What are the areas that communicate b/w brain areas that regulate feeding behaviour? (4)
-cortico-limbic system (reward, learning + memory, executive control) <— visual/olfactory/auditory stimuli + cues
-hypo (master nutrient sensor, incentive motivation)*
-hindbrain (oromotor + autonomic controls, satiation) *
= ingest -> taste -> gut -> absorbed + stored nutrients
** result in endocrine + autonomic outflow (most important)
Brain areas classification for regulating feeding behaviour (3)
autonomic:
-sensing of nutrional or energy reserve status (homeostatic signals)
- relaying homeostatic signals to the forebrain
-controlling adaptive thermogenesis
executive: (PFC + Nacc)
-decision to eat + to commit exercise
reward: (ventral tegmental area + limbic system (amygdala)
- establishing the hedonic + incentive or motivational salience properties of eating-related stimuli
Dorsal vagal complex info (5)
- Bi-directionally connected to peripheral organs via the vagus
- Direct nutrient and hormone sensing
- Contains neurons expressing a variety of neuropeptides
- Meal control and processing of sensory information
-Sends direct projections to the hypothalamus (PVN
The (important) hypothalamic nuclei (4)
- ARC
-VMN
-PVN
-SCN
CNS regulation of energy homeostasis balance (4)
balance b/w food intake + energy expenditure
- nutritional (e.g. glucose)
- humoral (e.g. leptin)
- nervous (e.g. vagal)
The central melanocortin system **
1) ME
2) ARC
3) PVN, LH, CEA, BST
4) LPB, RET
5) DMV
6)
Proopiomelanocortin (POMC) info (5)
- Neurons containing POMC found in the ARC (possibly NTS)
- Corticotropes of the pituitary also produced POMC
- Cleaved by prohormone convertases to a variety of peptide that have differential effects
- Cleavage products have different affinities for the different melanocortin receptor subtypes (1-5)
-Agonist activity of the MSH peptides on MC4R inhibits feeding
Loss of POMC function causes… (3)
- Obesity (lack of MC3R or MC4R agonism)
- Endocrine abnormalities (adrenal insufficiency; lack of MC2R agonism)
-Changes in pigmentation (lack of MC1R agonism)
How does Leptin directly regulate POMC neuron activity? (3)
- Fasting decreases hypothalamic POMC mRNA
–Can be reversed following leptin treatment
–Leptin-deficient ob/ob mice do not show fasting-induced regulation of POMC
-POMC neurons in the ARC and NTS are directly responsive to leptin
–Express leptin receptors
–Show pSTAT3 expression after leptin treatment
-Loss of leptin receptors on POMC neurons causes enhanced weight gain
