Diencephalon

Epithalamus

Hypothalamus

Thalamus clacifications

Epithalamus:

1-Pineal gland

2-Habenular nuc.(trigon)

3-Post.comissure

4-Stria medularis thalami

Pars ventralis

Hypothalamus:

1-Anterior nuc. Group

2- Medial nuc. Group

3-Lateral nuc. group

1- Reticular nuc.

2- Zona incerta

3- Nucleus of the fields of Forel

4- Subthalamic nuc.

Subthalamus

(Ventral thalamus):

Thalamus proper (thalamus):

Pars dorsalis

Metathalamus: Ventral & lateral geniculate nuc

1 Medial nuc. Group

2-Lateral nuc. group

Epithalamus

Pineal bodyHabenular trigonesStria medullaresPosterior commissure

Habenular nuclei

Pineal gland or Epiphysis

HYPOTHALAMUS HYPOTHALAMUS

Boundaries : 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

Hypothalamus

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

•LaterallyLateral 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 bundle2- Dorsal longitudinal fasciculus3- Mammillary efferent fibers4- Descending hypothalamic projections5- Hypothalamocortical fibers6- Supraoptic decussations7- Supraopticohypophysial tract8- 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 control of parasympatheticparasympathetic activitiesactivities

Coordination of the autonomic nervous system

Mamillary body

Hypothalamus Mesencephal Mesencephal tegmentaltegmental

Mamilotegmental tract

Mamilotegmental tract

Medial forbrain bundleMedial forbrain bundle

Periventricular fibersPeriventricular fibers

Polysynaptic con

nections

Polysynaptic con

nections

Parasympathetic nucleus Parasympathetic nucleus of brain stemof brain stem

autonomic nucleus of autonomic nucleus of spinal cordspinal cord

Dorsal longitudina

l fasciculus D

orsal longitudinal fasciculus

LacrimalLacrimalSalivatorySalivatoryGI tractGI tract

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 A:

Supraoptic n. (ADH) Kidney:1) reabsorption of renal water,Nacl & bicarbonate2) 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