Physiology of hypothalamus

 

Functions of the hypothalamus

This is the main vegetative functional organ of the diencephalon. It is responsible for the control of the autonomic nervous system, the diffuse neuroendorine system, the endocrine system itself and also emotional and behavioral mechanisms, since it is a part of the so called mesolimbic system. Its functions can be resolved therefore into two main ones as follows

  • Endocrine function

  • Vegetative functions

Endocrine function
Hypothalamus controls the anterior pituitary via release/release inhibiting  hormones (or factors) which enter the portal circulation that finally reaches the anterior pituitary through the tuberoinfundibular tract. Gonadotropin release factor (GnRF) acts on
gonadotroph to release gonadotropins such as FSH and LH. Somatotropin release factor or growth hormone release factor (GHRF) acts on somatrotroph. Thyrotropin releases factor (TRF) acts on thyrotrophs while corticotropin release factor (CRF) acts on corticotrophs. Prolactin inhibiting factor (PIF) and prolactin release factor (PRF) act on lactotroph according to their factions.

Also growth hormone release inhibiting factor also called somatostatin act negatively on the somatrotrophs of the anterior pituitary to to cause them to reduce the production of growth hormone. It also inhibits the secretion of insulin, gastrin, serotonin and thyrotropin.

 

The neurohypophysis consists of the posterior pituitary itself which is pars posterior or pars nervosa together with some infundibular parts such as the infundibular stem and median eminence, all of which are parts of the hypothalamus. The posterior pituitary gland (pars posterior)  is directly connected to the central nervous system by the tract known as the hypothalamohypophyseal tract consisting of nerve fibers which run from the supraoptic and paraventricular nuclei of the hypothalamus. The fibers in this tract deliver the hormones oxytocin and vasopressin to the neurohypophysis which are bound to the glycoprotein called neurophysin. The neurohypophysis contains neuroglia cells and some cells called pituicytes with undefined function. The cells that carry the neurohormones are paraneurons (or neurons).

 

Blood flows into the median eminence from the hypophyseal arteries carrying release factors from the hypothalamus. They are then drained by the capillaries of the median eminence (capillary 1) from where they enter the portal vessels that carry the same blood to the pars anterior. At the pars anterior the release factors act on the chromophils (sammatotroph [e.g. growth hormone release factor-GHRF]), mammotroph, corticotroph, thyrotroph and gonadotroph. Blood then flows into capillary 2 from where it drains into the hypophyseal veins and to general circulation carrying the hormones of the pars anterior such as growth hormone.

Vegetative functions of the hypothalamus are many and are as follows


Basic parts of brain 2  -3 D model

 

 

 

 

 

 

 

 

 

 

 

 

Neurohormone secretion through axons into the posterior pituitary

 

 

 

Brainstem Medulla Pons Midbrain Thalamus Epithalamus
Basal ganglia Forebrain Temporal lobe Cerebral operculum Remove operculum Wall of lateral ventricle 1
Wall of lateral ventricle 2 Wall of lateral ventricle 3 lateral ventricle 1 lateral ventricle 2 Base of brain Rhomboid fossa

 

 

 

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