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lec 20

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Doug Mac Kay

20 Hypothalamus and limbic systemOctober 26 2007Controller and programmer of autonomic functionsMicturition urinationVoiding the bladderoreflex and programmed controlSacral reflex parasympathetic oWhen bladder fills up it stretchesbladder stretch receptors embedded in the muscle walls of the bladderPontine centers organizeo1 sequence of relaxation of external sphincter muscle and pelvic floor musclespromotes urinationo2 continenceprevents urination sphincter muscles contractedPAG zone selects between continencemicturitionHypothalamus medial preoptic nuclei amygdala limbic frontal lobe influence PAGoPutting urination within social contextHomeostasisMaintenance of a stable internal body environment milieu intrieurproduct of many physiological control circuits negative feedback loopsoregulated by feedback loopshypothalamus is major coordinator of homeostatic controlHypothalamus is major regulator of core parameters such as plasma glucose energy osmolality keep water regulatednot flooded or drying out tissue temperaturesensors located within hypothalamus to detect changes in these parametershypothalamus can communicate directly to endocrine system via pituitary body with hormonesoalso has connections to brainstem ANS and motor centres ex PAGcorrective actions initiated involving autonomic endocrine and somatomotor mechanisms to release hormonesHypothalamusInteracts with brainstem motor and autonomic centers via axonal projectionsinteracts with endocrine system via pituitarycan coordinate complete physiological response to challenges to internal environmentPituitary Bodyprovides an interface between CNS and endocrine system2 modes to communicate with hypothalamuso1 axonal projectionsrelease of hormone from terminals eg ADHneurons from hypothalamus project to pituitary body and release hormones into the blood stream near pituitary bodydirecto2 releasing hormone intermediarycarried to pituitary in portal system ex CRH1
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