Question

Sleep and Metabolism To maintain a stable weight, there must be energy balance. Energy intake is equal to energy expenditure. However, when this energy balance is disrupted it can lead to individuals who are underweight or overweight. Maintaining proper energy balance involves complex interactions among several organ systems in the body. In the hypothalamus there is a satiety center and a hunger center. Leptin is an anorexigenic (i.e., satiety) signal, whereas ghrelin is an orexigenic signal (i.e., promotes appetite). Leptin is a peptide hormone produced by adipocytes. Ghrelin is a peptide hormone produced by gastric cells in the stomach. There are leptin receptors and ghrelin receptors in the hypothalamus. A. (6 pts.) Considering the satiation pathway (i.e., what makes you feel "full" after a meal), identify the: Stimulus, Receptor, Control Center, Effector, and Response. You must explain your choices. B. (8 pts). From its point of origin, trace how a molecule of ghrelin will move through the circulatory system (including through the heart) and ultimately bind to a receptor in the hypothalamus (nervous tissue). [You are not required to discuss named arteries and veins, other than the ones discussed in the videos and during ICAs).

Answer 1

A. Satiation pathway is controlled by a number of factors. Satiety centre (ventromedial nuclei) is present in the hypothalamus along with the feeding centre (lateral nuclei). After eating the glucose levels increases which trigers the satiation centre and causing fullness of feeding. Moreover ghrelin is a peptide hormone secreted from the GI tract which causes stimulation of the feeding centre as a result feeding is done.it is released in response to hunger(stimulus). It acts on the receptors on NPY neurons of the hypothalamus (control centre). Now after feeding ghrelin decreases as a result the feeding centre is not activated and satiety centre(effector) gets activated which causes withdrawal of feeting with satiety (response).

B. Ghrelin is released from the GI tract ( also from pancreas, lungs, adrenals,brain) in response to hunger. Now it is secreted into blood and through portal vein is taken to Inferior vena cava and through heart to the hypothalamus. Here it acts on the NPY receptors on the neurons which gives orexigenic stimulus by stimulating lateral nuclei of hypothalamus containing feeding centre and as a result the act of feeding is done.

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