PHYS - Regulation of Food Intake Flashcards
What are the neuronal centers that regulate feeding and satiety and where are they located?
Lateral Nucleus Ventromedial Nucleus Paraventricular Nucleus Dorsomedial Nucleus Arcuate Nucleus
All located in the hypothalamus
What are orexigenic?
Chemical signals that increase appetite
What are anorexigenic?
Chemical signals that suppress appetite
How does the anorexigenic pathway work?
Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus release alpha-MSH on MCR-4 receptors at neurons in the Paraventricular Nucleus
alpha-MSH is secreted in response to POMC neurons detecting anorexigenics
When Paraventricular Nucleus neurons recieve alpha-MSH at their MCR-4 receptors, they signal appetite suppression
How does the orexigenic pathway work?
Neuropeptide-Y (NPY) secreting neurons in the Arcuate nucleus release NPY on Y1R receptors on Paraventricular Nucleus neurons
Additionally, these same neurons secrete Agouti-Related Peptide (AGRP), which is an MCR-4 receptor ANTAGONIST
NPY secreting neurons secrete NPY and AGRP in response to orexigenics, and in response, neurons of the paraventricular nucleus signal an increase in appetite
THINK OF THE FOLLOWING
AGRP (Stomach growl) NPwhY am I so hungry??
What is Ghrelin?
It is gastric hormone secreted by endocrine cells in the stomach
OREXIGENIC
It stimulates NPY-secreting neurons in the arcuate nucleus by binding to Growth Hormone Secretagogue Receptors (GHSR)
Causes:
- Increased appetite
- Increased gastric motility
- Increased gastric acid secretion
- Increased adipogenesis
- decreased insulin secretion (maybe, no concensus)
INITIATES FEEDING RESPONSE
What is Insulin?
It is a pancreatic hormone secreted by pancreatic beta cells
ANOREXIGENIC
It stimulates POMC neurons in the arcuate nucleus, causing stimualtion of anorexigenic pathway and inhibiting orexigenic pathway
- Decreases appetite
- increases metabolism
EXCEPTION: In patients with Type 1 diabetes, there is an association with increased food intake with decreased insulin levels
What is CCK?
It is a small bowel hormone secreted from I Cells of the duodenum
ANOREXIGENIC
It causes a decrease in Ghrelin secretion from the stomach, acts on Vagus N. -> NTS -> hypothalamus pathway, and inhibits gastric emptying, causing an increase in gastric distension
What is PYY?
PYY is a bowel hormone secreted from L Cells in the ileum and colon
ANOREXIGENIC
It acts as a NPY-secreting arcuate nucleus neuron INHIBITOR
NYP neurons normally increase appetite, thus PYY will cause appetitie suppression
What is Leptin?
Leptin is an Adipose Tissue hormone, secreted from adipocytes
ANOREXIGENIC
Leptin acts on both POMC and NYP-secreting neurons
Leptin inhibits the actions of NYP-secreting neurons, and promotes the actions of POMC neurons
Actions:
- Suppresses appetite
- Increases metabolism
- DECREASE GHRELIN SECRETION
What is GIP?
Glucagon-Like Peptide, it is a bowel hormone that is secreted from L Cells in the Ileum and Colon (same cells that secrete PYY)
ANOREXIGENIC
Secreted after a meal
Actions:
- Decreases appetite
- Suppresses glucagon secretion
- Delays gastric emptying; increasing gastric distention
What is Oxyntomodulin?
It is a proglucagon derived peptide. Released from L Cells of the ileum and colon in response to ingested food (in proportion to caloric intake)
ANOREXIGENIC
What is Pancreatic Peptide?
Secreted from Islets of Langerhans of the pancreas
ANOREXIGENIC
Pancreatic Peptide is assumed to directly interact with Y4R receptors, inhibiting action of NPY-secreting neurons, resulting in appetite suppression
What is Glucagon?
Pancreatic hormone secreted by alpha cells of the pancreas
ANOREXIGENIC
Increases blood glucose levels and insulin secretion
Suppresses appetite
What is amylin?
Pancreatic hormone stored and secreted in Beta cells of the pancreas with insulin.
ANOREXIGENIC
Released in response to food intake
Inhibits NPY release
