Hypothalamus and Its Connections PDF

(004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21...

(004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 OUTLINE II. GENERAL APPEARANCE of HYPOTHALAMUS I. HYPOTHALAMUS Caudally, the hypothalamus merges into the tegmentum of the II. GENERAL APPEARANCE of midbrain. The lateral boundary of the hypothalamus is formed by HYPOTHALAMUS the internal capsule A. CORONAL VIEW B. SAGITTAL VIEW III. STRUCTURES ASSOCIATED A. CORONAL VIEW IV. 4 REGIONS OF HYPOTHALAMUS A. PREOPTIC REGION B. SUPRACHIASMATIC REGION C. TUNERAL REGION D. MAMILLARY REGION V. FUNCTION of the HYPOTHALAMUS A. REGULATE HORMONE AND ENDOCRINE B. CONTROLS AUTONOMIC NERVOUS SYSTEM VI. BLOOD SUPPLY  Cingulate VII. PATHWAYS gyrus which is a part of the limbic system  Thalamus is lateral to the 3rd ventricle  Lateral to the thalamus is the internal capsule which separates the thalamus from the basal ganglia. I. HYPOTHALAMUS  Basal ganglia: caudate nucleus Putamen Globus pallidus (externa & interna) Hypothalamus  Two Hypothalamic nuclei- below and in front of the thalamus Location: within the diencephalon;ventral- anterior B. SAGITTAL VIEW to thalamus (0.3% of the total brain) *** Remember the other three structures of the diencephalon the epithalamus, metathalamus and thalamus in the dorsal  Midbrain- highest portion of the brainstem. Pons and posterior portion of the diencephalon. Hypothalamus is actually medulla. located ventrally and anterior to the thalamus. There’s another  Thalamus- on top of the superior and inferior colliculi structure that’s ventral to the thalamus and that’s subthalamic  Hypothalamus- ventrally anterior to the thalamus nucleus which is a part a part of the basal ganglia. Page 1 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 III. STRUCTURES ASSOCIATED Optic chiasm Hypothalamus Hypothalamus: is in the highest order in this axis  Consist of 4 regions closely related to optic chiasm (part of the visual pathway)  Closely associated with pituitary gland  Hypothalamus, pituitary gland and adrenal gland and all the target organs will form a part of the HPA axis (hypothalamic pituitary adrenal axis)  HPA axis (hypothalamic pituitary adrenal axis) regulates endocrine function. Associated with thalamus, pituitary gland, optic chiasm and mamillary bodies mamillary body: termination of fornix -Mammillary body is in the posterior portion of the hypothalamus. And terminal portion of the fornix closely related a part of the hippocampus  Amygdaloid bodies -inferior medial surface aspect of the temporal lobe Thalamus Page 2 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 HYPOTHALAMUS: Four regions Rostral to caudal (preoptic>suprachiasmatic.tuberal>mamillary) 1. Preoptic region- lateral and medial preoptic nuclei 2. Anterior (supraoptic) region aka suprachiasmatic region Paraventricular nucleus Supraoptic nucleus 3. Middle region aka tuberal region ventromedial, dorsomedial and arcuate nucleus Hypothalamus-Lateral view (mamillary bodies) 4. Posterior region aka mammillary region Mammillary bodies -Terminal portion of the fornix Located in the posterior portion of the hypothalamus Two main functions of the hypothalamus 1. Regulate hormone production or endocrine function 2. Controls autonomic nervous system  Anterior commissure will connect the temporal lobe.  Commissural fibers will connect the left and right cerebrum Corpus callosum- biggest commissure that connects the left and right cerebrum.  Anterior commissure- connects the two temporal lobes also share the olfactory and audio-visual information All regions will contain different nuclei and have specific function Hypothalamus: mamillary bodies (coronal view) A. PREOPTIC REGION VI. 4 REGIONS OF HYPOTHALAMUS 1.Preoptic region (nuclei)- Will contain releasing hormones for the sex hormones: GNRH (Gonadotropin-releasing hormone) that acts on the anterior pituitary that produces the FSH and LH  Lateral preoptic nuclei  Medial preoptic nuclei Page 3 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 B. SUPRACHIASMATIC REGION o Dorsomedial nucleus- regulates emotion and behavior o Arcuate nucleus- Regulates prolactin and growth hormone and β endorphin for pain  Produce all the other hormones that will affect the other endocrine hormone from the pituitary (TRH Thyrotropin- releasing hormone – that will act on the pituitary that will produce the thyroid-stimulating hormone TSH) *TSH- anterior pituitary *TRH-hypothalamus * corticotropin releasing hormone CRH- act on the anterior pituitary for it to release ACTH (Adrenocorticotropic hormone) that will act on the adrenal gland *GHRH (Growth hormone-releasing hormone) - act on the 2.Suprachiasmatic region (nuclei)- Responsible of the production of anterior pituitary for it to release its growth hormone that will two hormones (ADH,OXYTOCIN) act on the bone and cartilages  Paraventricular nucleus *also contain a neuro transmitter dopamine that inhibits the  Supraoptic nucleus production of prolactin from the anterior pituitary because 1. ADH (Anti-diuretic hormone) aka vasopressin- act on the prolactin should be inhibited in a normal non-pregnant state kidney tubules to conserve water and prevent using a lot of or in men. ***In males’ hypothalamus produce dopamine that water in the body. will inhibit the production of prolactin from the anterior 2. Oxytocin- responsible for milk let down pituitary gland. Suprachiasmatic nucleus- regulates the circadian rhythm along with the pineal gland which secretes melatonin (Receive inputs from the retina that will tell where there is light or darkness) D. MAMILLARY REGION hypothalamus: coronal view (anterior nucleus)  anterior nucleus – regulates thirst C. TUBERAL REGION 4. Mammillary Region- Mammillary body: Closely related to hippocampus Limbic system for emotion, behavior and memory Lateral Hypothalamic Nucleus (and MFB)  Hypocretin (orexin) hypothalamus: coronal view (Tubelar Region) Feeding center (regulation of feeding) Secrete hypocretin (orexin) for appetite 3.Tuberal region  Narcolepsy, reward o Ventromedial nucleus VMN – satiety center Posterior Nucleus Page 4 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 V. FUNCTION of the HYPOTHALAMUS (Gnrh: act on pituitary for FSH and LH production)  Autonomic Nervous System (ANS) Two main functions of the hypothalamus  Arcuate Nuclei (Tuberal Nuclei): produce hypothalamic releasing factors, contains dopaminergic neurons that inhibit 1. Regulate hormone production or endocrine function prolactin release, contains beta endorphin – a role in opiate 2. Controls autonomic nervous system analgesia.  Anterior commissure will connect the temporal lobe.  Commissural fibers will connect the left and right cerebrum DOPAMINE is dominant so that prolactin will not be produce  Corpus callosum- biggest commissure that connects the left During pregnancy dopamine is inhibited to produce prolactin and right cerebrum  Anterior commissure- connects the two temporal lobes also DIRECT: From supraoptic and paraventricular nuclei via – share the olfactory and audio-visual information hypothalamo-hypophyseal tract – secretion of neuroendocrine products (OXYTOCIN, VASOPRESSIN) into general circulation via vasculature of posterior pituitary. (Note: production of ADH and oxytocin transported by axonal transport and contain in the posterior pituitary (doesn’t produce hormone only stores) INDIRECT: From Tuberal nuclei (arcuate) via tuberoinfundibular tract. Secretion of releasing hormones (e.g. GHRF, LRF) into portal plexus which influences release (of other substances -GH, LH, TSH, ACTH, FSH, PROLACTIN) by anterior HYPOTHALAMUS: Autonomic Function B. CONTROLS AUTONOMIC NERVOUS SYSTEM  Anterior Nucleus: thermal regulation (dissipation), stimulation of parasympathetic NS, destruction results in hyperthermia  Posterior Nucleus: thermal regulation (conservation of heat) stimulation of sympathetic NS, destruction results in inability to thermoregulate  Suprachiasmatic Nucleus: receives input from retina, mediates circadian rhythms Electrical stimulation of anterior and preoptic region-influence parasympathetic response. Stimulation of posterior and lateral nuclei causes sympathetic response “Head Ganglion” of autonomic system:  Regulates almost all autonomic functions such as: body A. REGULATE HORMONE AND ENDOCRINE temperature (preoptic area), heart rate, blood pressure, bladder contraction, hunger (paraventricular)  Connections to reticular system and raphe nuclei of  Paraventricular and Supraoptic nuclei: regulate water brainstem balance, produce Antidiuretic Hormone (ADH, a.k.a. - Dorsal Longitudinal Fasciculus vasopressin) and oxytocin. Destruction causes Diabetes Insipidus LIMBIC FUNCTION: (Oxytocin: act on the uterus for uterine contraction and on o Dorsomedial Nucleus the nipples for milk letdown) o Emotional behavior o Stimulation results in obesity and savage  Preoptic Nuclei: contain sexually dimorphic nuclei, regulate o Behavior (sham rage) release of gonadotropic hormone Page 5 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 The hypothalamus is supplied with blood by small branches of the VI. BLOOD SUPPLY Circle of Willis HYPOTHALAMUS AND PITUITARY HYPOTHALAMUS- contain hormone-secreting cells INTERACTS WITH PITUITARY (pea sized gland at the base of hypothalamus)  Anterior Pituitary - From Pre-Optic nucleus o Ventromedial Nucleus - Tubero -infundibular tract to Median eminence, then o Satiety center via Portal veins o Destruction results in obesity and savage - Gonadotropic releasing hormone behavior  Posterior Pituitary o Stimulation inhibits feeding - Supraoptic-hypophyseal tract o Lateral Nucleus - ADH/Vasopressin (supraoptic nuclei) o Feeding center(thirst center) - Oxytocin (paraventricular nuclei) o Stimulation induces eating ***Posterior lobe: storage for ADH (water retention and o Destruction results in loss of appetite, conservation) and oxytocin (uterus contraction and milk anorexia, starvation down then hypothalamus will release o Mammillary Nucleus Hypothalamus: Releasing Hormones: CRH, TRH, o Input from hippocampal formation GnRH Inhibiting Hormone: DopamineProduces o Lesions result in memory deficits ADH, Oxytocin o Projects to anterior nucleus of the thalamus. Remember: Anterior nucleus: release of heat Posterior: conservation of heat Dorsomedial: emotional behavior Ventromedial: satiety center Lateral: feeding Mammillary: Memory Regulation of emotional behavior - o Anger- o Rage-stimulation of lateral hypothalamic nuclei and lesion of ventromedial nucleus o Sexual activity VII. PATHWAYS Pathways to and from parts of Limbic System parallel each other: 1. AMYGDALA via stria terminalis 2. HIPPOCAMPUS & SUBICULUM via fornix (to and from mammillary bodies) 3. SEPTAL NUCLEI, OLFACTORY CORTEX, SUBICULUM via medial forebrain bundle (MFB) 4. THALAMUS – Mammillo-thalamic tract Page 6 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 Page 7 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 Test your Knowledge 1. Which of the following statements concerning the 4. Hemorrhagic lesions in the mammillary bodies hypothalamus is correct? A. It is a division of the subthalamus B. It contains the tuberculum cinereum C. Its suprachiasmatic nucleus receives input from retina D. It is not related to the limbic system 5. Associated with the Rathke pouch E. Its dorsomedial and the ventromedial nuclei are separated by the striae medullares 2. Which of the following is a hypothalamic structure? A. Alveus 6. Destruction of the anterior hypothalamic nuclei B. Arcuate C. Column D. Crus E. Fimbria 7. Stimulation of the ventromedial nuclei Select answer for no.3-9) A. Anorexia 8. Bilateral lesions of the ventromedial hypothalamic nuclei B. Craniopharyngioma C. Diabetes insipidus D. Hyperthermia E. Inability to thermoregulate 9. Bilateral lesions of the posterior hypothalamic nuclei. F. Obesity and savage behavior 3. Amenorrhea and galactorrhea 10. Destruction of the supraoptic and paraventricular nuclei. Page 8 of 9 CMED 1B  (004) HYPOTHALAMUS AND ITS CONNECTIONS DR. ELTON ONG | 01/06/21 ANSWERS 1. C. The suprachiasmatic nucleus of the hypothalamus 9. E. Bilateral lesions of the posterior hypothalamic nuclei result receives direct input from the retina and plays a role in the in the inability to thermoregulate (poikilothermia). Bilateral control of circadian rhythms. The tuberculum cinereum destruction of only the posterior aspect of the lateral overlies the spinal trigonal nucleus. The limbic system has hypothalamic nucleus results in anorexia and emaciation. reciprocal connections with the hypothalamus. The striae medullares separate the dorsal aspect of the pons from the dorsal aspect of the medulla. 10. C. Destruction of the supraoptic and paraventricular nuclei or the supraopticohypophyseal tract results in diabetes 2. B. The arcuate nucleus is a periventricular nucleus in the insipidus with polydipsia and polyuria. tuber cinereum. It contains neurons that produce. hypothalamic-releasing factors and gives rise to the tuberohypophysial tract. The alveus, fimbria, crus, and column are components of the fornix. REFERENCES 3..G. Amenorrhea and galactorrhea result from a prolactin- secreting pituitary adenoma, the most common type of pituitary adenoma. 1. PPT – Doc Ong, M.D. 2. BRS- 5th Edition Douglas J. Gould 3. Snell’s Clinical Neuroanatomy 8th Edition 4. H. Hemorrhagic lesions in the mammillary bodies and in the periaqueductal gray of the midbrain are seen in Wernicke encephalopathy. 5. B. Craniopharyngiomas—congenital epidermoid tumors— are derived from the Rathke pouch; they are the most common supratentorial tumors found in children. 6. D. Destruction of the anterior hypothalamic nuclei results in hyperthermia. 7. A. Stimulation of the ventromedial nuclei inhibits the urge to eat, resulting in emaciation (cachexia or anorexia). Destruction of these nuclei results in hyperphagia and savage behavior. 8. F. Bilateral lesions of the ventromedial hypothalamic nuclei result in hyperphagia and savage behavior. Page 9 of 9 CMED 1B