1. Thalamus
Prof. K. Sivapalan

2. Superior and Medial Relations
Large gray matter on either side of the third ventricle
The superior surface forms the floor of the central part of the lateral ventricle.
The medial surface forms the greater part of the wall of the third ventricle
Inter thalamic adhesion [connexus] connect the two thalami
Inferiorly, hypothalamus and behind it ventral thalamus are related to thalamus
4/17/2019
Thalamus & hypothalamus

3. Thalamus & hypothalamus
Other Relations
Hypothalamic sulcus , running from the inter ventricular foramen to the aqueduct, seperates the hypothalamus.
Anterior end lies just behind the inter ventricular foramen
Posterior end [called pulvinar] lies just above and lateral to the superior colliculus of the midbrain.
Two nuclei, medial and lateral geniculate bodies lie at the posterior end.
The lateral surface is related to internal capsule
4/17/2019
Thalamus & hypothalamus

4. Thalamus & hypothalamus
Internal Structure
Thalamus is made up of several nuclei.
Y shaped sheet of white matter placed vertically divides it into three major portions: anterior, medial and lateral.
Each part contains several distinct nuclei
4/17/2019
Thalamus & hypothalamus

5. Thalamus & hypothalamus
Connections
Fibers from most parts of the brain converge in thalamus
Exteroceptive and proprioceptive impulses in spinothalamic tract and medial leminiscus relay before being projected to sensory cortex
Visual impulses go to lateral geniculate body and auditory impulses to medial geniculate body and to respective cortices
Taste sensation is conveyed to thalamus through solitariothalamic fibers
Olfactory impulses reach thalamus probably through amygdaloid complex
Visceral information comes from the hypothalamus
All parts of the cerebral cortex, cerebellum and corpus striatum project to thalamus.
4/17/2019
Thalamus & hypothalamus

6. Thalamus & hypothalamus
Connections Ctd.
The thalamus projects to all parts of the cerebral cortex through thalamocortical projections
Efferent projections from thalamus go to corpus striatum, hypothalamus, and the reticular formation.
Function:
The thalamus is regarded as a great integrating centre.
Integration of all impulses.
Some degree of perception exteroceptive sensations- specially pain.
4/17/2019
Thalamus & hypothalamus

7. Thalamus & hypothalamus
Is the ventral portion of the anterior end of diencdephalon.
It lies below the hypothalamic sulcus on both sides of the third ventricle.
It contains many nuclei.
4/17/2019
Thalamus & hypothalamus

8. Thalamus & hypothalamus
Relations
Medially it forms the wall of the third ventricle
Laterally it is in contact with internal capsule and posteriorly with the ventral thalamus.
Anteriorly extends up to the lamina terminalis and merges with the olfactury structures.
Inferiorly, tuber cinereum, infundibulum and mamillary bodies which are considered as parts of hypothalamus.
4/17/2019
Thalamus & hypothalamus

9. Connections of the Hypothalamus.
4/17/2019
Thalamus & hypothalamus

10. Functions of theHypothalamus.
Temperature regulation- anterior hypothalamus responds to heat, posterior hypothalamus responds to cold.
Catecholamine secretion- through limbic function- dorsal and posterior hypothalamus.
ADH, Oxitocin- supraoptic and paraventricular nuclei.
Other pituitary hormones- paraventricular, preoptic, periventricular, and arcuate nuclei.
Thirst- lateral superior hypothalamus.
Hunger- venteromedial, arcuate, paraventricular and lateral nuclei.
Sexual behavior- [anterior ventral hypothalamus and piriform cortex] and reproduction – GRH, ? puberty
Defensive reactions- fear, rage- diffuse.
Endocrine and activity rhythms- suprachiasmatic nucleus.
4/17/2019
Thalamus & hypothalamus

11. Autonomic Nervous System.
Visceral function is regulated by autonomic reflexes and endocrines.
Many reflexes are coordinated at spinal level- bladder, rectum, and sexual reflexes- input from higher centers also.
Blood pressure, respiration, swallowing, coughing, sneezing, gagging and vomiting are coordinated in brain stem- medulla oblongata.
Light reflex is coordinated in midbrain.
Temperature regulation and many complex mechanisms are coordinated in hypothalamus.
4/17/2019
Thalamus & hypothalamus

12. Thalamus & hypothalamus
4/17/2019
Thalamus & hypothalamus

13. Thalamus & hypothalamus
4/17/2019
Thalamus & hypothalamus