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noun, plural: Orexins

An endogenous peptides that is active in modulating sleep-wake cycle integrating metabolic,circadian and sleep debt influences and other hypothalamic functions.


Orexins acts as neurotransmitter that regulates wakefulness, appetite and arousal. There are symptoms associated due to lack of Orexins in the brain that damage the cells to produce it such as narcolepsy that loses muscle tone. In the brain contains only few cells that generates Orexins about 10,000-19,000 neurons in the hypothalamus. Motivation of these receptors by orexins boosts intracellular calcium levels in hypothalamic cells.

Orexins are high excitatory neuropeptide hormones in the brain that excite various nuclei that affects dopamine, histamine, acetylcholine and norepinephrine system that stabilizes organisms sleep cycles, once it is bind to the orexin receptor which is G protein coupled receptor it will then linked to the sense molecules outside the cell and trigger signal transduction pathways to bring forth cellular responses.

Orexin deficit will make an organism sleepy wherein glucose level inhibited a particular class of glucose-sensing neurons to produce tiny protein orexins though it is still strange how glucose hold back the electrical activity of orexin cells thus, initially involved in the stimulation of food intakes that encourage energy expenditure.

Word Origin: orexis= “appetite

Gene name: HCRTR1

Protein name: Orexin receptor type 1


Hypocretin receptor type 1


See also:

Circadian clock

Metabolic rate