Diencephalon

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Diencephalon:

Diencephalon Dr Pankaj Maheria

PowerPoint Presentation:

Part of brain between the cerebrum and brainstem. Third ventricle Two major subdivisions : Pars dorsalis Pars ventralis Hypothalamic suclus

Divisions and subdivisions:

Divisions and subdivisions Pars dorsalis : Thalamus Metathalamus which includes the medial and lateral geniculate bodies Epithalamus Pineal body (gland ) Habenular nuclei and commissure Posterior commissure Stria medullaris thalami. Pars ventralis Subthalamus Hypothalamus

Thalamus :

Thalamus

PowerPoint Presentation:

Large ovoid mass of grey matter laying above the midbrain. 3.5cm in length and 1.5cm in breadth. Long axes: Obliquely running backwards and laterally. Interthalamic adhesion Functionally , the thalamus is generally considered as the great sensory gateway to the cerebral cortex. It receives impulses from the opposite half of the body and transmits most of them to the sensory area of the cerebral cortex ( areas 3, 2, and 1 ).

External features: :

External features: Ends : two Anterior Posterior Surfaces : Four Superior Inferior Medial Lateral

Ends :

Ends Anterior end: Narrow Tubercle of thalamus . Posterior boundary of interventricular foramen. Posterior end: Pulvinar

Surfaces::

Surfaces: Superior surface : Lateral part: Floor of central part of lateral ventricle. Medial part : tela choridea of 3 rd ventricle Inferior surface: Anterior part : fused with subthalamus Posterior part: free , forming the inferior aspect of pulvinar .

Surfaces::

Surfaces: Medial surface : Lateral wall of 3 rd lateral ventricle. Lateral surface: Medial boundary of posterior limb of internal capsule.

Internal structure : white matter :

Internal structure : white matter External medullary lamina Stratum zonale . Internal medlullary lamilla .

Internal structure : Grey matter :

Internal structure : Grey matter Internal medullary lamina Nuclei Anterior Medial Lateral

Thalamic nuclei :

Thalamic nuclei Nuclei in the anterior part: Anterior nucleus. Nuclei in the medial part Medial dorsal nucleus Medial ventral nucleus.

Thalamic nuclei: lateral part :

Thalamic nuclei: lateral part Dorsal part : Lateral dorsal (LD) Lateral posterior (LP) Pulvinar (P) Ventral part Ventral anterior (VA) Ventral lateral (VL) OR ventral intermediate (VI) Ventral posterior (VP) . Ventral posterolateral nucleus (VPL) Ventral posteromedial nucleus (VPM)

Thalamic nuclei:

Thalamic nuclei Intralaminar nuclei Midline nuclei ( paraventricular ) Reticular nucleus Medial and lateral geniculate bodies

Connection of Thalamus:

Connection of Thalamus

Connection of Thalamus:

Connection of Thalamus

Connections of Ventral Group of nuclei:

Connections of Ventral Group of nuclei Ventral posterior nucleus Terminations of the major sensory pathways ascending from the spinal cord and brainstem

Connections of Ventral Group of nuclei:

Connections of Ventral Group of nuclei

Connections of Ventral Group of nuclei:

Connections of Ventral Group of nuclei Ventral anterior nucleus: Connections: largely unknown. Probably receives fibres from the globus pallidus and cerebellar nuclei, and sends efferents to the cerebral cortex (parietal lobe, anterior part). Functions : unknown.

Connections of lateral group of nuclei:

Connections of lateral group of nuclei

Connections of lateral group of nuclei:

Connections of lateral group of nuclei

Connections of lateral group of nuclei:

Connections of lateral group of nuclei

Connections of anterior nucleus:

Connections of anterior nucleus Afferents : Mamillary body through the mamillothalamic tract. Efferent fibres: Gyrus cinguli (23, 24 32) Function : Attention and memory

Connections of medial dorsal nucleus:

Connections of medial dorsal nucleus Division : Magnocellular part Parvocellular part Function : Mood and emotional balance.

Connections of Intralaminar nuclei:

Connections of Intralaminar nuclei Division Anterior group Posterior group

Connections of midline nuclei:

Connections of midline nuclei

Medial & Lateral Geniculate Bodies:

Medial & Lateral Geniculate Bodies

Medial Geniculate Body:

Medial Geniculate Body A relay station on auditory pathway. Part : Medial Ventral Dorsal nuclei

Lateral Geniculate Body:

Lateral Geniculate Body Relay station on the visual pathway. Position : Inferior surface of the pulvinar Anterolateral to the medial geniculate body. It is smaller than the medial geniculate body Connected to the superior colliculus by superior brachium

Lateral Geniculate Body:

Lateral Geniculate Body

Epithalamus :

Epithalamus

Pineal gland (epiphysis cerebri):

Pineal gland (epiphysis cerebri ) A midline cone-shaped reddish grey structure (only 3mm X 5mm in size) occupying the vertical groove between the two superior colliculi below the splenium of corpus callosum . It has a stalk which divides into two laminae . Ventral ( inferior) lamina is continuous with the posterior commissure Dorsal ( superior) lamina is continuous with the habenular commissure . Pineal recess.

Unique features:

Unique features Pineal gland is the only part of the brain, which has no nerve cells in it. It is the only part of the brain which is supplied by a nerve ( nervus conarii ) which arises from outside the brain.

Paraventricular nuclei:

Paraventricular nuclei

Habenular Nucleus:

Habenular Nucleus Position : Habenular trigone

Connections of the habenular nuclei.:

Connections of the habenular nuclei. Habenulopineal Tract

Habenular Commissure :

Habenular Commissure Connects the habenular nuclei of the two sides and crosses the midline by passing through the superior lamina of the stalk of pineal gland

Posterior Commissure:

Posterior Commissure Composite bundle of fibres which connect the medial longitudinal fasciculi , interstitial nuclei, superior colliculi , pretectal nuclei and posterior thalamic nuclei of the two sides. It crosses the midline by passing through the inferior lamina of the stalk of the pineal gland

Hypothalamus :

Hypothalamus

PowerPoint Presentation:

A part of diencephalon which lies below the thalamus. Small in size weighing only 4 g and forming only 0.3% of the total brain mass The hypothalamus controls three systems: (a) autonomicnervous system, (b) endocrine system, and (c) limbic system. The hypothalamus helps to maintain the homeostasis

Boundaries of the hypothalamus:

Boundaries of the hypothalamus Anteriorly: Lamina terminalis Posteriorly: Subthalamus . Inferiorly: Structures in the floor of third ventricle. Superiorly: Thalamus. Laterally: Internal capsule. Medially: Cavity of third ventricle.

Subdivisions of the hypothalamus:

Subdivisions of the hypothalamus

Hypothalamic nuclei:

Hypothalamic nuclei Hypothalamic regions and nuclei in them. Medial zone ( Periventricu lar and intermediate) Lateral zone Preoptic region Preoptic nucleus Supraoptic region Paraventricular nu . Periventricular cell groups Suprachiasmatic nu. Intermediate cell groups (= anterior nucleus ?) Supraoptic nucleus Tuberal region Dorsimedial nucleus Ventrimedial nucleus Arcuate ( infundibular ) nucleus Premamillary nucleus Lateral tuberal nucleus Mamillary or posterior region Posterior nucleus (lies partly in tuberal region) Tuberomamillary nucleus Mamillary body Mamillary nuclei

Connections:

Connections

Connections: Afferent :

Connections: Afferent Visceral afferents (including those of taste) through the spinal cord and brainstem Afferents from the nucleus of the solitary tract Somatic afferents reach the hypothalamus through collaterals of major ascending tracts.

Connections: Afferent :

Connections: Afferent Afferents from olfactory pathways, and to the limbic system. Medial forebrain bundle Olfactory impulses

Connections: Afferent :

Connections: Afferent Afferents from olfactory pathways, and to the limbic system. Medial forebrain bundle Olfactory impulses Visceral impulses Locus coeruleus

Connections: Efferent:

Connections: Efferent Mammillothalamic tract Mammillotegmental tract Descending fibres to the brainstem and spinal cord

Connections: Afferent :

Connections: Afferent Fornix connects the hippocampus to the mammillary bodies. Stria terminalis connects the amygdaloid body to the preoptic and anterior hypothalamic nuclei. Mammillary peduncle conveys sensory impulses from the spinal cord and the brainstem to the lateral hypothalamic nucleus. Medial forebrain bundle connects the autonomic and limbic structures of the forebrain to the hypothalamus. Thalamohypothalamic , pallidohypothalamic and subthalamohypothalamic pathways connect the thalamus, corpus striatum and subthalamus to the hypothalamus respectively. Direct physical and chemical receptors. The circulating blood is constantly monitored by the hypothalamic cells, which function as thermo receptors, osmoreceptors or chemoreceptors .

Connections of the hypothalamus with hypophysis cerebri (pituitary gland):

Connections of the hypothalamus with hypophysis cerebri (pituitary gland)

Connections: Afferent :

Connections: Afferent Medial forebrain bundle Mamillary peduncle

Connections: Afferent :

Connections: Afferent Medial forebrain bundle Mamillary peduncle Dorsal longitudinal fasciculus

Thank you…:

Thank you…

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