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Thalamus .ppt
The thalamus is located in the center of the cerebral hemispheres. It receives sensory input from various areas and projects to different cortical regions. The thalamus and cortex work as a single functional unit, with the thalamus integrating inputs and the cortex performing higher-level processing. Anatomically, the thalamus is divided into anterior, lateral, and medial groups of nuclei. The lateral group contains sensory relay nuclei that project to sensory cortices. Association nuclei in the medial and dorsal groups integrate sensory and limbic inputs and project to association cortices. Nonspecific nuclei in the intralaminar and midline regions are involved in arousal, emotions, and alertness. Damage to the
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Thalamus .ppt
- 1. Thalamus Dr. Pandian M. AssistantProfessor Dept. of Physiology ZMCH, Dahod.
- 2. Diancephalon – interbrain -Thalamus - Medial & lat geniculate bodies - Pineal body – melatonin secretion - Hypothalamus - Subthalamus
- 3. Introducton:- o Placed inthe centre of cerebral hemisphere o Neurons project to various areas of cortex o Input from sensory system, motor structures ARAS and cortex THALAMUS & CORTEX WORK AS SINGLE UNIT THALAMUS (integration of Inputs)
- 4. THALAMUS Intermediate mass Third ventricle Anterior • Partof diecephalon • Clusters of nuclei • Medially lines 3rd ventricle •Laterally lines Internal capsule Ext. medullary lamina
- 5. • Internal medullarylamina – -- Y-shaped band of fibers -- Intermingled with nuclei • 3 major areas – »Anterior »Lateral »Medial Divisions of Thalamus Internal medullary lamina
- 6. Anatomical Subdivisions ofThalamus Ant. N. Lat.gr. Med. Gr. Ventral gr. Dorsal gr. Ventroanterior Ventrolat. Ventroposterior LGB MGB Dorsolat. Posterolat. Pulvinar Dorsomedial Centromedial Midline intralaminar
- 7. I. Lateral group A.Ventral nuclei Ventroanterior ( BG) Ventrolateral (cerebellum& BG) Ventro posterior VPL VPM Med. & Lat. Geniculate bodies (Control vol. movements) (vol. movements) (Main sensory relay) (Auditory and visual relay) Ventral nuclei Dorsal nuclei
- 8. Nucleus Input outputFunction VA BG, prefrontal Pre motor cortex Vol. Movements VL Cerebellum, GPi, area 4,6 Motor cortex Primary, PMA Vol. Movements VPL & VPM Somatosensory pathway Sensory cortex (1,3 &2) Specific Sensory relay LGB Visual input Primary visual cortex Visual relay MGB Auditory input Primary aud. area Auditory relay
- 9. B. Dorsal GroupDorsolateral (LD) (Speech) Posterolateral (LP) (control of motor functions) Pulvinar (integration of sensations)
- 10. II. Dorsal Group NucleusInput Output Function Pulvinar (large in man) LGN, MGN., sup.colliculi Asso. & visual Cortex PTO Cortex Visual attention Dorsolateralis (LD) Uncertain Cingulate gyrus Speech formation Posterolateralis (LP) Visual, association areas, pulvinar, VPL PTO Cortex Motor function
- 11. II. MEDIAL GROUPDorsomedial (emotional feeling with sensations, personality, procedural memory) Intralaminar N. (alerting effect) Midline N. (visceral sensation) Centromedian N.
- 12. II. MEDIAL GROUP •A) Intralaminar nuclei • Input from ARAS, BG, • output to Prefrontal cortex • Integration of somatic sensation, and alerting effect • B) Midline Nuclei • Input from sensory pathways, reticular formation And from locus ceruleus (noradrenergic) and raphe nuclei (serotonergic) • output to hypothalamus, and Neocortex • Integration of visceral sensation, arousal
- 13. C) Dorsomedial Nuclei •Input from amygdala, hypothalamus • Project to frontal association area • Emotional feeling with sensation & personality, procedural memory D) Centromedial Nucleus - ??
- 14. III. ANTERIOR GROUP •Anterior Nuclei (Attention Memory and Emotions) Input from Mammillothalamic Tract Project to cingulate gyrus – part of Papez circuit
- 15. Functional groups ofthalamic nuclei I. – Sensory relay nuclei II. - Association nuclei III. – Nonspecific nuclei IV. – Motor nuclei Specific nuclei Nonspecific nuclei
- 16. I. Sensory nuclei– Ventrobasal complex (VP), LGB, MGB Input – ML, STT, Corticothalamic Projection – Somatosensory Cx II. Association nuclei – • Pulvinar, DL, PL, DM • Input - Sensory Cx, Asso. Cx, Limbic system • Projection – Asso. Cx, Limbic system
- 17. III. Nonspecific nuclei– (emotions, arousal) • Midline, Intralaminar • Input – STT, RF, corticothalamic • Projection – Diffusely to Cx, limbic system IV. Motor nuclei - VA, VL Input - GP, Prefrontal Cx., dentatothalamic ( cerebellum) Projection – premotor Cx, P.moror Cx.
- 18. THALAMOCORTICAL UNIT /SYSTEM Thalamus plays imp. role in all major divisions of nervous system viz. sensory, motor & motivational. All nuclear groups have to & fro connections with cerebral Cx. Thus thalamus and Cx function as one unit. Probably thalamus prepares a crude blue print of final product achieved by the Cx.
- 19. FUNCTIONS OF THALAMUS 1.Sensory relay station and modulating centre 2. Maintenance of conscious alert state 3. Subcortical perception of pain,temp.,crude touch 4. Control of muscular movements 5. Visual attention and visually guided movements –(pulvinar) 6. Integrating centre for sleep 7. Recent memory and emotions 8. Concerned with speech 9. Synchronization of EEG
- 20. THALAMIC SYNDROME –(of Dejerine – Roussy) • Blockage of Thalamogeniculate artery- branch of post. Cerebral artery • Damage to VP & posterolateral nucleus of dorsal group • Symptoms on opposite side & accompanied by emotional disturbance. • Involvement of sensory, motor and emotional functions
- 21. Sensory effects –on opposite side temporory loss of discrimination, localization stereognosis permanent loss of kinesthetic sensations results in ataxia After few weeks over reaction to painful stimuli – thalamic pain Thalamic phantom limbs –Alien hand syndrome Pt. finds difficulty in locating his own hand when the eyes are closed. He catches in air to locate them or illusion that limb is lost..
- 22. • Motor effects– »Due to involvement of dentato-thalamico- cortical fibers »Muscle weakness, »Intention tremors »Thalamic hand »Choreoathetosis- involvement of fibers from globus pallidus • Emotional effects – intense emotions - pleasant or unpleasant
- 23. Thalamic hand – flexionand pronation at wrist, flexion at MP joint, hyperextension at IP joint. During recovery, spontaneous excruciating pain on opposite side of body due to dominance of pain fibers ending on medial nuclei.
- 24. References • Text bookof Medical Physiology 14th edition Guyton & Hall • Ganong's Review of Medical Physiology, 26 edition. • Human Physiology – Vander • Text book of Medical Physiology – Indukurana • Principles of Anatomy and Physiology – Totora • Hutchinson Clinical Methods • Net source for pictures
- 25. THANK YOU .. .