THALAMUS AND HYPOTHALAMUS

THALAMUS AND HYPOTHALAMUS

Prof.Sangeeta Singhal

Department of Physiology JNMC ALIGARH

INTRODUCTION:-

 The term thalamus derives from a Greek word that means “ inner chamber” or meeting place.

Paired ,oval ,nuclear mass of 30×20×20 mm

The largest component 80% of the diencephalon

The term diencephalon includes the following structures:-

 Epithalamus

 Thalamus

 Hypothalamus and

 Subthalamus

Thalamus is most important sensory relay station .

Ascending fibers synapse in thalamus and are then projected to the cortical sensory areas.

It also receives impulses from the ascending Reticular formation which it relays to cerebral cortex.

The two thalami form the floor and lateral walls of the third ventricle of brain.

Separated from hypothalamus by hypothalamic sulcus.

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1-NEUROANATOMIC CLASSIFICATION:-

 Divided by internal medullary lamina into three nuclear groups:-

Lateral group of nuclei

Medial group of nuclei

Anterior group of nuclei



Lateral group of nuclei



2 types :- dorsal and ventral group of nuclei



Ventral group:- 1-Ventral anterior nucleus 2-Ventral posterior nucleus

3-Ventral lateral nucleus Dorsal group:- 1-Lateral dorsal nucleus

2-Lateral posterior nucleus

3-Pulvinar nuclei

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:-

1- DORSOMEDIAL NUCLEUS



Anterior group of nuclei:-



Anterior thalamic nuclei

• OTHER NUCLEI:- 1-

2-Intralaminar nuclei

3-Reticular nucleus

4-Medial and lateral geniculate bodies

PHYSIOLOGICAL CLASSIFICATION:-

On the basis of functions nuclei are classified into:-

1-Specific sensory relay nuclei

2-Specific motor nuclei

3-Association nuclei

4-Limbic system nuclei

CONNECTIONS OF T^HALAMUS

NEUROTRANSMITTERS AND NEUROPEPTIDES IN

T^HALAMUS:-

GABA is the inhibitory NT in local circuit neurons ,reticular nucleus and lateral geniculate nucleus

Glutamate and Aspartate are the excitatory NT in corticothalamic and thalamocortical projection neurons

Many neuropeptides, like substance P, Somatostatin and Enkephalin

FUNCTIONS OF THALAMUS:-

1-RELAY CENTER:- impulses of almost all the sensations reach the thalamic nuclei, after being

processed in the thalamus the impulses are carried to cerebral cortex

2-CENTER FOR PROCESSING OF SENSORY INFORMATION

3- Role IN AROUSAL and ALERTNESS REACTIONS

4-CENTER FOR REFLEX ACTIVITY

5-CENTER FOR INTIGRATION OF MOTOR ACTIVITY:- through the connections with

cerebellum and basal ganglia.

APPLIED PHYSIOLOGY

THALAMIC SYNDROME :- also known as

“Dejerine-Roussy disease”.

Caused due to infarct in geniculothalamic artery , a branch of posterior cerebral artery.

The clinical hallmark is a pan sensory loss contralateral to the lesion, paraesthesia, and thalamic pain.

Transient hemiparesis, homonymous hemianopia, hemi ataxia, tremor and spatial neglect, all

contralateral to the lesion in the thalamus.



Thalamic hand:-

and pronated at the wrist and metacarpo-phalangeal joints and extended at inter phalangeal joints. (due to involvement of posterolateral nucleus)



Thalamic phantom limb:-

he catches it in the air as if it is lost.(due to involvement of posteroventral nucleus)

HYPOTHALAMUS

Hypothalamus is described as “The Head ganglion of the autonomic nervous system” by Sherrington.

It is a small bilateral structure extends from the region of optic chiasma to the caudal border of the

mammillary bodies.

It is below the Thalamus ,very small in size (wt 4 gm only )

PARTS OF THE HYPOTHALAMUS

The hypothalamus is subdivided into optic, tuberal and mammillary parts . The nuclei present in each part are as follows:

OPTIC PART:- 1- Preoptic and supraoptic nuclei 2-Paraventricular nucleus

3-Suprachiasmatic nucleus

Tuberal part:- 1-Ventromedial nucleus 2-Dorsomedial nucleus 3-Tuberal nucleus

4-Arcuate nucleus Mammillary part:- 1-Posterior nucleus

2-Lateral nucleus 3-Mammillary body

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 1-Endocrine control

2-General autonomic effect

3-Temperature regulation

4-Food intake

5-Thirst –fluid regulation

6-Sleep and wakefulness

7-Circadian rhythm

8-Sexual behaviour and reproduction

9-Emotion, fear, rage, aversion , pleasure and reward