Regulation of Metabolism during Post Absorptive State
Both hormones and the sympathetic NS regulate metabolism during this state. The hormones counter the effects of insulin and are sometimes called “anti-insulin” hormones. As blood glucose levels decline, the secretion of insulin decreases, and the release of anti-insulin hormones rises. As blood glucose levels drop, the pancreas releases glucagon at a faster rate, making the beta cells secrete insulin more slowly. Glucagon primarily targets the liver with the major effect being increasing the release of glucose into the bloodstream due to gluconeogenesis and glycogenolysis. Low blood glucose also activates the sympathetic NS. Neurons in the hypothalamus detect low blood glucose and increase sympathetic output. As a result, nerve endings release NT norepinephrine , and the adrenal medulla releases both epinephrine , and norepinephrine into the bloodstream. Epinephrine stimulates glycogen breakdown. Epinephrine and norepinephrine are also potent stimulators of lipolysis. The actions of these NT/hormones help increase glucose and free fatty acids for ATP production, and more glucose is available to the nervous system. ***Keep in mind that historically horses are meant to graze up to 20 hours/day. Most domestic horses today don’t have that luxury and based on the stable management practices of that particular farm will affect the horse’s metabolism***
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