Hypothalamus and Pituitary Gland PDF

Hypothalamus and Pituitary Gland  Hypothalamus The hypothalamus is a region of the brain that controls number of bodily functions. It is located in the middle of the base of the brain, and encapsulates the ventral portion of the third ventricle. It extends from the regi...

Hypothalamus and Pituitary Gland  Hypothalamus The hypothalamus is a region of the brain that controls number of bodily functions. It is located in the middle of the base of the brain, and encapsulates the ventral portion of the third ventricle. It extends from the region of the optic chiasma to the caudal border of the mammillary bodies. It forms the lower border of the mammillary bodies. It forms lateral wall below the hypothalamic sulcus.  Anterior to the hypothalamus is an area that extends forward from the optic chiasma to the lamina terminalis and the anterior commisure, preoptic area. Caudally the hypothalamus merges into the tegmentum of the midbrain. Superior to the hypothalamus lies the thalamus inferolaterally is subthalamic region.  The Diencephalon Fornix divides the hypothalamic nuclei into medial and lateral groups thalamus Epithalamus hypothalamus (Pineal & Optic chiasm Habenula) Mammillary pituitary subthalamus body Hypothalamus Anatomy Lines the walls of 3 rd ventricle, above the pituitary. Divided into medial and lateral regions by the fornix, bundles of fiber tracts that connect the hippocampus to the mamillary bodies.  Below the hypothalamus it is related to the structures at the floor of third ventricle; Optic chiasma Tuber cinereum and infundibulum Mammillary bodies Preoptic area We have lamina terminalis. On the anterior side, we have the lamina terminalis Divisions of the Hypothalamus 3rd ventricle  Tuber cinerum is convex mass of gray matter continous in between mamillary bodies and infundibulum. There are tuberal nuclei deep to tuber cinerum. Median eminence is the elevation caused by tuberal nuclei.  Neurohypophysis Median eminence infundibulum posterior lobe of hypophysis cerebri  Hypothalamus is divided into medial and lateral zones for purposes of description by fornix and mamillothalamic tract.  Medial Zone Preoptic Anterior Suprachiasmatic Paraventricular Dorsomedial Ventromedial Infundibular Posterior  Lateral Zone Preoptic Suprachiasmatic Supraoptic Lateral Tuberomammillary Latreal tuberal but when you take a look at the medial group, the medial group of nuclei can be divided into three sets, anterior, middle, and posterior pvn Divisions of the Hypothalamus periventricular medial lateral Divisions of the Hypothalamus Divisions of the Hypothalamus Both oxytocin and ADH are going to be they use this hypothalamic-hypophysial produced in hypothalamus. And these are portal system. It's like a portal circulation. going to be via axonal transport, physical So the controlling hormones produced transport. They are going to be brought to from hypothalamus, they are going to be the posterior pituitary gland and secreted secreted to the bloodstream here, and via to the bloodstream from the posterior this superior hypofysial artery and the pituitary gland. hypothalamic-hypophysial portal system, Tuberoinfundibular tract Hypothalamic- Hypophysial Portal System Hypothalamohypophysial tract they use this hypothalamic-hypophysial portal system. It's like a portal circulation. So the controlling hormones produced from hypothalamus, they are going to be secreted to the bloodstream here, and via this superior hypofysial artery and the hypothalamic-hypophysial portal system, Through the bloodstream, these controlling hormones, they are going to come to the anterior pituitary and they are going to control the production and release of these individual hormones produced in the anterior pituitary gland. Okay  Afferent connections of hypothalamus Hippocampohypothalamic fibers- main output of limbic fibers Thalamohypothalamic fibers Corticohypothalamic fibers Amygdalohypothalamic fibers Olfaction travels through the medial forebrain bundle Visceral and somatic afferents reach hypothalamus through collateral branches of the lemniscal afferent fibers and through the reticular formation Tegmental fibers arise from the midbrain Fibers from locus caeruleus ( a center related to sleep)  Efferent Connections Mammilothalamic tract arises in the mammillary bodies , end in anterior nucleus of thalamus Mammillotegmental tract ( terminates in reticular formation, affects the muscle activity) Descending fibers to brainstem and spinal cord influence the peripheral neurons of the autonomic nervous system. Hypothalamus is also connected to hypophysis by neural pathways and blood vessels.  Functions It has autonomic functions; regulates the sympatic and parasymphatetic functions. Endocrine control; by relaesing and relaese inhibiting factors control production of ACTH, FSH, LH, TSH, GH, MSH, LTH [prolactin] Temperature regulation regulation of food and water intake; hunger center is lateral part, satiety center is at medial part, bodily expression of emotion is going to be thirst center lateral region from hypothalamus via Emotion and behavior the autonomic nervous system. It Control of circadian rhythms  the posterior pituitary gland. The posterior pituitary gland is the place of secretion of antidiuretic hormone, which is going to hold up water, trying to increase the blood and it releases, it secretes oxytocin, which induces the breast tissues and uterus. The ADH and oxytocin, these are going to be produced in hypothalamus and physically, via axonal transport, via nerve tracts, these are going to be transported to the posterior pituitary and released in the posterior pituitary. anterior pituitary, which is the the thyroid gland and induce the thyroid adenohypophysis. This produces the growth gland to produce the thyroid hormones, hormone, adrenocorticotropic hormone, the the T3 and T4. And let's take a look at FSH ACTH, thyroid-stimulating hormone, follicle- and LH. These are going to be going on stimulating hormones, and prolactin. We do finding these gonadal organs and they're not see prolactin produced this anterior going to be in the males is going to be pituitary gland produces and secretes inducing the production of testosterone, stimulating hormones. The stimulating whereas in the females, progesterone and hormones. The stimulating hormones are also estrogen are going to be produced from called tropic hormones. Stimulating hormones these target endocrine organ target are tropic hormones. These stimulating endocrine organs, they need tropic hormones, they find their endocrine targets hormones to act and produce their own and they stimulate certain hormones. Take a eventual hormones. And these eventual look. ACTH, adrenocorticotropic hormone, is hormones are going to be the ones which going to go on and stimulate the cortex of go on to the blood circulation and affect adrenal gland, adrenocorticotropic. It induces all the body. The thyroid, the adrenals, the cortex of the adrenal gland to produce testosterone steroid hormones. Thyroid stimulating hormone from But how are we going to limit the production and how are we going to control the production of these eventual target hormones? Meaning the adrenal corticosteroids, the thyroids, the testosterone and estrogen. They are circulating in the bloodstream and they go back. 52:08 to the anterior pituitary and negatively affect these cells here in addition to the travel to the hypothalamus where they would have another negative effect. So there is a negative feedback effect both on the hypothalamus and on the pituitary gland to tell them stop inducing, stop releasing, stop stimulating. Functions of the Hypothalamus Autonomic nervous Anterior area system regulation influences PSNS Hormone production through projections Endocrine regulation to brainstem PSNS Circadian rhythm nuclei regulation Posterior area Limbic system interaction influences SNS Various through projections – Temperature to the lateral gray regulation horn – Feeding Functions of the Hypothalamus Autonomic nervous Magnocellular regions of the system regulation supraoptic and Hormone production paraventricular nuclei Endocrine regulation produce oxytocin and Circadian rhythm vassopressin (ADH) regulation Transported via axonal Limbic system interaction transport systems Various (hypothalamohypophysial – Temperature tract) to neurohypophysis regulation Released in circulation – Feeding Damage to supraoptic n.  diabetes insipidus Functions of the Hypothalamus Autonomic nervous Stimulating or inhibiting system regulation hormones are Hormone production Endocrine regulation transported via the Circadian rhythm tuberoinfundibular tract regulation and released in to the Limbic system interaction pituitary portal system Various and ultimately to the – Temperature adenohypophysis regulation – Feeding Functions of the Hypothalamus Autonomic nervous Input from retina to system regulation suprachiasmatic Hormone production Endocrine regulation nucleus is then sent Circadian rhythm through poorly regulation defined projections Limbic system interaction to the pineal gland Various – Temperature regulation – Feeding Functions of the Hypothalamus Autonomic nervous system regulation Temperature Hormone production – Posterior n. conserves heat Endocrine regulation – Anterior n. dissipates heat Circadian rhythm – Fever starts – sweating regulation – Fever ends – chills Limbic system interaction Feeding Various – Lateral n. induces eating – Temperature – Ventromedial n. inhibits regulation eating – Feeding  Pituitary Gland Hypophysis a roundish organ that lies immediately beneath the hypothalamus, in the sella turcica ("Turkish saddle") 500mg in adult  The anterior pituitary or adenohypophysis is a classical gland composed predominantly of cells that secrete protein hormones.  The posterior pituitary or neurohypophysis is not really an organ, but an extension of the hypothalamus. It is composed largely of the axons of hypothalamic neurons which extend downward as a large bundle behind the anterior pituitary. It also forms the so-called pituitary stalk, which appears to suspend the anterior gland from the hypothalamus.  Hypophysis is supplied by two sets of arteries;branches of internal carotid artery. The superior hypophysyseal artery forms an arterial ring around the upper part of the infundibulum and inferior hypophysyseal artery forms an arterial ring around the posterior lobe and give branch to lower infundibulum. They form tuft of capillaries and these capillaries drain into long and short portal veins and they end in the anterior lobe of hypophysis by dividing into vascular sinusoids that pass between the secretory cells of the anterior lobe. The portal system carries the releasing and release inhibiting hormones which are produced in the hypothalamus. The control of anterior lobe is done.  Regulation of Pituitary Hormone Secretion Hypothalamic-pituitary axis Hypothalamo- hypophyseal Hypothalamo- portal blood hypophyseal vessels to neural tract to anterior neural lobe of pituitary gland pituitary gland Principles of Neural Science, 4th Ed. Kandel, Schwartz and Jessell, p. 977  A key to understanding the endocrine relationship between hypothalamus and anterior pituitary is to appreciate the vascular connections between these organs. The secretion of hormones from the anterior pituitary is under strict control by hypothalamic hormones. These hypothalamic hormones reach the anterior pituitary through the following route: A branch of the hypophyseal artery ramifies into a capillary bed in the lower hypothalamus, and hypothalmic hormones destined for the anterior pituitary are secreted into that capillary blood. Blood from those capillaries drains into hypothalamic-hypophyseal portal veins. Portal veins are defined as veins between two capillary beds; the hypothalamic-hypophyseal portal veins branch again into another series of capillaries within the anterior pituitary. Capillaries within the anterior pituitary, which carry hormones secreted by that gland, joins with veins that drain into the systemic venous blood. Those veins also collect capillary blood from the posterior pituitary gland.