Diencephalon
Epithalamus Hypothalamus
Thalamus clacifications 1-Pineal gland 2-Habenular nuc.(trigon) 3-Post.comissure 4-Stria medularis thalami Epithalamus: 1-Anterior nuc. Group 2- Medial nuc. Group 3-Lateral nuc. group Pars dorsalis Thalamus proper (thalamus): Metathalamus: Thalamus clacifications Ventral & lateral geniculate nuc 1 Medial nuc. Group 2-Lateral nuc. group Hypothalamus: Pars ventralis 1- Reticular nuc. 2- Zona incerta 3- Nucleus of the fields of Forel 4- Subthalamic nuc. Subthalamus (Ventral thalamus):
Epithalamus Pineal body Habenular trigones Stria medullares Posterior commissure
Habenular nuclei
Pineal gland or Epiphysis
HYPOTHALAMUS
Boundaries : Hypothalamus Superior : The hypothalamic sulcus separating it from the thalamus Inferior : Optic chiasma , tuber cinereum and mamillary bodies . Anterior : Prepotic area ( from optic chiasma to the lamina terminalis and anterior commissure ) Poster : The tegmentum of the mid brain Medial : The third ventricle Lateral : The internal capsule & optic tract
Cytoarchitectural organization (Nuclei) : Medially 1- Anterior hypothalamic region Suprachiasmatic Supraoptic Preoptic Anterior Paraventricular 2- Middle hypothalamic region Arcuate or infundibolar Ventromedial dorsomedial 3- Posterior hypothalamic region Mamillary body posterior Laterally Lateral Lateral tuberal
Afferent connections : 1- Medial forebrain bundle 2- Hippocampo-hypothalamic fibers 3- Amygdalo-hypothalamic fibers 4- Brainstem afferents 5- Retino-hypothalamic fibers 6- Cortico-hypothalamic fibers 7- Forebrain afferents
Efferent connections : 1- Medial forebrain bundle 2- Dorsal longitudinal fasciculus 3- Mammillary efferent fibers 4- Descending hypothalamic projections 5- Hypothalamocortical fibers 6- Supraoptic decussations 7- Supraopticohypophysial tract 8- Tuberohypophysial tract
Functional considerations : 1- Coordination of the autonomic nervous system 2- Regulation of body temprature 3- Maintenancce of water balance 4- Control of anterior pituitary 5- Control of reproductive functions 6- Control of growth 7- Control of food intake 8- Control of emotional behavior 9- Hypothalamus and sleep
Three Methods of Hypothalamic Control over the Endocrine System
Control of anterior pituitary
Coordination of the autonomic nervous system Autonomic functions : - Water balance - internal secretion - sugar and fat metabolism - temprature regulation Chief subcortical center for the regulation of both sympathetic & parasympathetic activities - ventricular portion of the tuber cinerum - Ant & med hyp. R. (supraoptic & preoptic) control of sympathetic activities - lat & post hyp. R. control of parasympathetic activities
Coordination of the autonomic nervous system autonomic nucleus of spinal cord Mamillary body Hypothalamus Polysynaptic connections Lacrimal Salivatory GI tract Mamilotegmental tract Medial forbrain bundle Mesencephal tegmental Periventricular fibers Dorsal longitudinal fasciculus Parasympathetic nucleus of brain stem
Regulation of body temprature hyperthermia Ant hypothalamus : sensitive to hyperthermia (hyperpyrexia) Mechanism for Dissipation of excess heat : 1) sweating 2) vasodilation of the cotaneous blood vessels 3) Thirst hypothermia Post hypothalamus: sensitive to hypothermia Mechanisms for heat conservation & heat production : 1) vasoconstriction of the cotaneous blood vessels 2) ceastion of sweat secretion 3)Augmentation of visceral activities oxidation 4)Shivering of somatic muscles Thus : Coordination of sympathetic & parasympathetic response regulation of body temprature
Maintenance of water balance Supraoptic n. (ADH) Kidney: 1) reabsorption of renal water,Nacl & bicarbonate 2) alter the osmotic permiability of water in the distal and collecting tubules B: Ant region on the hyp thirst consumption of water C: Lat hypo at the level of ventromedial n. Reduction in water intake
Control of growth : GH releasing factor Ant lobe of hypophysis Growth of bone & soft tissue
Ventromedial n. :Satiety Control of food intake Lat hypothalamic n. : feeding center
Control of emotional behavior 1) Lat region of the ant hyp : flight responses 2) Ventromedial n. : aggressive responses Coordination of sympathetic & parasympathetic response
Hypothalamus and sleep Tuberomammillary n. Raphe n “sleep centers” Pontine reticular formation Intralaminar & reticular thalamic nuclei