Chapter 12: BRAIN MECHANISMS Flashcards
What do neural circuits in the brain stem control?
chewing and swallowing behaviours involved in eating
What is decerebration?
-surgical procedure that severs the brain stem, disconnecting the hindbrain from the forebrain
Role of area postrema and nucleus of the solitary tract?
- receive signals and send information to regions of forebrain to help control food intake
- events that produce hunger increase the activity in those areas.
- lesions of this region abolish both glucoprivic and lipoprivic feeding
What is lateral hypothalamus involved in ?
- initiation of eating
- produces melanin-concentrating hormone (MCH) and orexin which stimulates hunger and decreases metabolic rate
Where do the axons of MCH and orexin project?
- regions of the brain involved in motivation, movement ad metabolism
- neocortex, periaqueductal grey matter, reticular formation, thalamus, locus coeruleus.
What is MCH (melanin-concentrating hormone)?
- 1 of 2 peptide NT found in lateral hypothalamus
- stimulate appetite
- reduce metabolic rate
What is orexin?
- 1 of 2 peptide NT found in lateral hypothalamus
- stimulate appetite
- reduce metabolic rate
- also called hypocretin
What is neuropeptide Y (NPY)?
- Peptide NT
- stimulator of food intake
- found in arcuate nucleus
- stimulates feeding, insulin and glucocorticoid secretion
- decreases breakdown of triglycerides
- decreases body temperature
What other orexigenic peptide is released by the terminals of hypothalamic NPY neurons?
- agouti-related peptide also known as AgRP
- like NPY, potent and extremely long-lasting orexigen.
How do endocannabinoids stimulate eating?
- By increasing the release of MCH and orexin.
- levels of cannabinoids highest during fasting and lowest during feeding.
How are cannabinoids used medically for ingestive behavior?
- cannabinoid agonists to increase cancer patients appetite
- cannabinoid antagonists as an aid to weight reduction
What are MCH and orexin activated by?
NPY/AgRP secreting neurons of the arcuate nucleus which also project to the paraventricular nucleus.
How does leptin produce its behavioural and metabolic effects?
- desensitizes the brain to hunger signals
- by binding on neurons that secrete NPY and AgRP.
- leptin inhibits them, and decrease their release.
What other peptide-secreting hormones than leptin serve as anorexigens?
- Cocaine and amphetamine-regulated transcript (CART)
- a-Melanocyte-Stimulating Hormone (a-MSH)
SLIDES 53, 54, 55
peptide summary!!!
