Thalamus and Hypothalamus

To MBBS 2nd year

03-03-2017

By Dr. Laxman Khanal

Assistant professor, department of anatomy

BPKIHS, Dharan

Introduction

• The diencephalon is the part of brain between the cerebrum and the brainstem. The cavity within it is termed third ventricle.

• Hypothalamic sulcus divides the diencephalon into pars dorsalis and pars ventralis.

• Pars dorsalis consists of thalamus, metathalamus and epithalamus.

• Pars ventralis consists of hypothalamus and subthalamus.

T3rd ventricle

Thalamus – 2 in number (right and left)Hypothalamus- single with right andleft half.

Epithalamus• Habenular nuclei• Pineal body

Interventricular foramen

Hypothalamic sulcusT

HT

Where does thalamus lie in horizontal section ?

Covered on its superior surfaceby a thin layer of white matter,called the stratum zonale.

• Covered on its lateral surface by anotherlayer, the external medullary lamina.

• Reticular nucleus lies outside of it.

The gray matter of the thalamus isdivided by a vertical sheet of whitematter, the internal medullary laminainto anterior, medial and lateral parts.

• Medial geniculate body• Lateral geniculate body• Subthalamus

Ventral part Dorsal part

• Dorsal tire nucleus• Ventral tire nucleus

• Anterior thalamus• Medial thalamus• Lateral thalamus

Intra-laminar nuclei

Q. What are the nuclei of thalamus ? Reticular nuclei Intralaminar nucleiNucleus of-1. Anterior thalamus2. Medial thalamus3. Lateral thalamus• Dorsal tire nuclei• Ventral tire nuclei

Anterior nucleus of thalamus• Adjust your mood with recent memory.• Have connection with limbic system• Component of Papez circuit

Cingulate gyrus

Mamillothalamic tract

Hippocampus

Prefrontal cortexConcerned with thought and behavior.

Dorsomedial nucleusAdjust behavior and physical andpsychological state according to your mood.

Intra-laminar nuclei

Trigeminal lemniscus

Spinothalamic pathway

Reticular formation

Intra-laminar nuclei act as a switch for Cerebral arousal by reticular formation.

Cauterization of these nucleihas been shown to relievesevere and intractable painassociated with terminalcancer.

LDLP

Pulvinar

1. Anterior thalamusAnterior nucleus of thalamus2. Medial thalamusDorsomedial nucleus3. Lateral thalamusA. Dorsal tire Lateral dorsal Lateral posterior PulvinarB. Ventral tire Ventral anterior Ventral lateral Ventral posterior VPM VPL

VP

VPL

VPM

Trigeminal lemniscusGustatory pathway

Long ascending tracts

Motor function

Thalamic syndrome

Thalamic pain

• Occurs as the patient is recovering from a thalamic infarct.

• The painful sensation may be aroused by light touch or by cold.

• May fail to respond to powerful analgesic drugs.

• Excessive pain might be due to overreaction of thalamus.

Thalamic handWrist is pronated and flexed, MPjoints are flexed and IP joints areextended with very littlemovements.

Hypothalamus

• It forms the floor and lateral wall of anterior part of 3rd ventricle.

• It controls 3 system

1. Autonomic nervous system

2. Endocrine system

3. Limbic system (emotional brain)

• Basically it has major role in maintaining homeostasis.

• Tuber cinerium• Median eminence• Mammillary bodies

Medial zoneLateral zone

Lateral zone is mainly occupied by long lateral nucleus (Hunger center)

4 regions 1. Pre optic 2. Supra-optic3. Tuberal4. Mammillary

Ant-Post division1. Preoptic region2. Supraoptic region3. Tuberal region4. Mammillary region

Preoptic region1. Preoptic nucleusSupra-optic region1. Anterior nucleus2. Supra optic nucleus3. Suprachiasmatic nucleus4. Paraventricular nucleusTuberal region1. Dorsomedial nucleus2. Ventromedial nucleus3. Arcuate nucleusMammillary region1. Posterior nucleus2. Mammillary nucleus

Preoptic region1. Preoptic nucleus

GnRH

FSHLH

Supra-optic region1. Supra-chiasmatic nucleus2. Anterior nucleus3. Supra-optic nucleus4. Paraventricular nucleus

Functions 1. Circadian rhythm2. AC (cooling mechanism) 3. ADH & oxytocin hormone

HHT- hypothalamo-hypophyseal tract

Tuberal region1. Arcuate nucleus2. Ventromedial nucleus3. Dorsomedial nucleus

Functions 1. Releasing factors2. Satiety & reward center3. Savage behavior

Mammillary region1. Mammillary nucleus2. Posterior nucleus

Functions1.• Behavior• Part of papez circuit2. • Heating center• Sympathetic center

Afferent connection• Visual afferent• Corticohypothalmic• Fornix• Stria terminalis• Thalamohypothalamic

tract • Tegmental fibers

Efferent connection• Descending hypothalamic

tract• Mammillothalamic tract• Mammillotegmental tract• HHT

Conclusion

• Thalamus acts as relay and integrative station for all the sensory information except smell.

• Hypothalamus lies anterior to and inferior to the thalamus. It is center of integration of autonomic and endocrine function.

• Both thalamus and hypothalamus makes the boundaries of 3rd

ventricle.

• Both thalamus and hypothalamus also play a role in memory and emotion.

There are many nuclei and it is very hard to remember…

But not impossible !!!!!!!!!