The hypothalamus is a part of the brain which plays an important role in the regulation of many vital physiological systems and in the maintenance of The Hypothalamus and the Concept of Neurosecretion The hypothalamus homeostasis Structure Endocrine role which depends on its close relationship with the pituitary gland The part of the brain which lies directly below the thalamus is connected to the pituitary hypophysis cid 127 Mainly comprised of neurons The median eminence lies outside the blood brain barrier Receives sensory and other information from all over the body Third ventricle divides the hypothalamus into left and right halves The anterior hypothalamus includes the supraoptic medial preoptic paraventricular and suprachiasmatic nuclei The middle hypothalamus includes the arcuate ventromedial and dorsomedial nuclei Three main efferent neuronal pathways Autonomic nervous system pain modulation cardiovascular and respiratory centers reward motivation and cognition behaviors brainstem parasympathetic nuclei down the spinal cord cid 127 Other parts of the brain Pituitary gland Blood supply to the hypothalamus Partly supplied with arterial blood by vessels coming from the circle of Willis cid 127 Most of the blood comes from the suprachiasmatic tuberal and hypophysial arteries Venous outflow is mainly via the anterior cerebral basilar and interpeduncular veins Specialized blood system called the hypothalamo adenohypophysial portal system Hypothalamic neurosecretions Neurotransmitters and hormones All molecules secreted by neurons are called neurosecretions If they are released across the synaptic gaps between a neuron terminal and the dendrites of another neuron then they are called neurotransmitters The hypothalamic neurons which comprise the efferent pathway passing down to the median eminence and those which pass through the median eminence to terminate in the posterior pituitary release their neurosecretions into blood true hormones In the median eminence the capillaries are fenestrated allowing molecules to enter the blood Exocytosis of granule contents results in the consequent release of the neurosecretory molecules which in this case enter the bloodstream through the These hormones act on specific anterior pituitary or adenohypophysial cells which they either stimulate or inhibit and so they are generally called releasing cid 127 Other hypothalamic hormones pass down through the pituitary stalk terminating in the neurohypophysis these hormones actually reach the general If GnRH is administered as a continuous infusion it inhibits the release of gonadotrophins from the anterior pituitary cid 127 When GnRH is given in pulses every 10 minutes it induces a normal pulsatile pattern of gonadotrophin release gaps of the capillary endothelial cells hormones or inhibiting hormones circulation and act on distant targets in the body The release of hypothalamic hormones is pulsatile Physiological role of the hypothalamus Important role as integration and control center Pituitary Tissue growth and maintenance cid 127 Metabolic regulation Appetite and food intake Temperature control Fluid balance Reproduction Lactation cid 127 Milk ejection Stress response Autonomic nervous system Cardiovascular regulation Blood pressure regulation Respiratory regulation Temperature control Fluid balance cid 127 Gastrointestinal function Stress response cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127