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Thalamus physiology
- 2. THALAMUS Thalamus is a ovoid mass of grey matter Thalamus present bilaterally slightly separated by third ventricle Thalamic nuclei: thalamus divided into 5 nuclear by intermedullary septum 1.Midline nuclei 2.Intralaminar nuclei 3.Medial mass of nuclei 4.lateral mass of nuclei 5.Posteriour group of nuclei
- 3. Mid line nuclei: ◦ These are the nuclei situated on medial side of thalamus ◦ Present near to midline ◦ Connections of midline nuclei: Afferent fibers from 1.Globas pallidus 2.Hypothalamus 3.Midbrain nuclei 4.Reticular formation Efferent fibers to Different areas of cerebral cortex
- 4. Intralaminar nucleil ◦ These are the nuclei present at medullary septum of thalamus ◦ Connections of Intralaminar nuclei: Afferent fibers from 1.Trigeminal lemniscus 2.Lateral lemniscus 3.Reticular formation Efferent fibers to 1.cerbrl cortex 2.Globaspallidus 3.other thalamic nuclei
- 5. Medial mass of nuclei: ◦ Situated medial to septum ◦ Has 2 nuclei Anterior nucleus Dorsomedial nucleus ◦ Connections of midline nuclei: Afferent fibers from 1.Mamillary body 2.Hypothalamus Efferent fibers to 1.Limbic cortex 2.Putamen and caudate nucleus 3.Hypothalamus 4.Prefrontal cortex
- 6. Lateral mass of nuclei: ◦ Situated lateral to septum ◦ It has divided into 2 groups Dorsal group Ventral group ◦ Dorsal group: Dorsal group of lateral mass with 2 nuclei 1.dorsolateral nucleus 2.posterolateral nucleus Ventral group of lateral mass with 3 nuclei 1.Anterior ventral nucleus 2.lateral ventral nucleus 3.Posteroventral nucleus
- 7. ◦ Connections of lateral mass nuclei: Afferent fibers from 1.Cortex 2.Parietal lobe 3.Globus pallidus 4.Dentate nucleus 5.Red nucleus 6.Trigeminal leminscus 7.Medial leminscus 8.Spinal leminscus Efferent fibers to 1.Cortex 2.Parietal lobe 3.Putamen and caudate nucleus 4.Premotor cortex 5.Precentral cortex 6.Hypothalamus 7.Cerebral cortex
- 8. Posterior group of nuclei ◦ Continuation of lateral mass of nuclei ◦ Having 2 groups Pulvinar Metathalamus 1.Medial geniculate body 2.Lateral geniculate body ◦ Connections of Posteior group of nuclei: Afferent fibers from 1.Inferior parietal lobe 2.Occipitl lobe 3.Auditory cortex 4.Optic tract Efferent fibers to 1.Inferior parietal lobe 2.Occipital lobe 3.Auditory cortex 4.Visual cortex
- 9. 1.Midline nuclei 2.Intralaminar nuclei 3.Medial mass of nuclei i.Anterior nuclei ii.Dorsomedial nuclei 4.lateral mass of nuclei i.Dorsal group >dorsolateral nucleus >posterolateral nucleus ii.Ventral group >Anterior ventral nucleus >lateral ventral nucleus >Posteroventral nucleus 5.Posteriour group of nuclei i.Pulvinar ii.Metathalamus >Medial geniculate body >Lateral geniculate body
- 10. Thalamic radiation: ◦ Thalamo cortical and cortico tahalamic fibers together form as a Thalamic radiation ◦ This tahalamic radiation pass through the internal capsule ◦ Divided into 4 groups called as thalamic peduncle or thalamic stalks 1.Anterior peduncle 2.Superior peduncle 3.Posterior peduncle 4.Inferior peduncle
- 11. ◦ Anterior peduncle: Connect the frontal lobe of cortex with medial and lateral thalamic nuclei Contain mostly motor nerve fibers ◦ Superior peduncle: Connect the post central gyrus of parietal lobe,adjacent area in frontal cortex with lateral mass of thalamic nuclei Contain mostly sensory nerve fibers ◦ Posterior peduncle: Connect the occipital lobe of cortex with pulvinar and lateral geniculate body Fibers concern with vision ◦ Inferior peduncle: Connect the temporal lobe of cortex With pulvinar and medial geniculate body Fibers concern with hearing
- 12. Functions of thalamus Relay center Almost all impulses sensations reach thalamic nuclei-->and b processed in thalamus --> impulses carried to cerebral cortex by thalamocortical fibers That’s why thalamus is relay center for sensations like pain touch etc Center of reflex activity Center for integration of motor functions Center for integration of sensory functions Center for sexual sensations Role in alertness reactions
- 13. Applied Physiology ◦ Lesion of thalamus leads to Thalamic syndrome ◦ It has features of Loss of sensations Astereognosis Unable to recognise the object by touch wit closed eyes Ataxia Incoordination of voluntary movements Thalamic phantom limb Unable to locate the position of limb Astereognosis Spontaneous pain Involuntary movements Athetosis:slow writing and twisting movements Chorea:quick jerky involuntary movements Intention tremors:involuntary movements of flexion and extension rhythemically at joints of fingers wrist and elbow
- 14. THANK YOU…!