Thalamus PDF

DIENCEPHALON 01.Thalamus (Dorsal thalamus) Pars Dorsalis 02.Metathalamus – Med Gen. Body - Lat. Gen. Body 03.Epithalamus - Pineal body...

DIENCEPHALON 01.Thalamus (Dorsal thalamus) Pars Dorsalis 02.Metathalamus – Med Gen. Body - Lat. Gen. Body 03.Epithalamus - Pineal body - Habenular Nuclei - Habenular Commissure Hypothalamic sulcus - Post. Commissure - Stria Medullaris Thalami Pars Ventralis 01.Subthalums (Ventral Thalamus) – Sub-thalamic Nucleus - Zona Inserta 02.Hypothalamus -  Diencephalon  Paired structure  Located between the brain stem and the cerebral hemisphere  Continuous with the mb rostral part of the p midbrain C mo  Forms the lateral wall of the 3rd ventricle  Thalamus Diencephalon Thalamus Hypthalamus Subthalamus Epithalamus Metathalamus (lateral & medial geniculate bodies)  Thalamus  Large mass of grey matter, in shape and size, resembles an egg  Forms the lateral wall of the 3rd ventricle  Separated from hypothalamus by hypothalamic sulcus  Connected to opposite thalamus by interthalamic adhesion (massa intermedia) thalamus Interthalamic adhesion Hypothalamic sulcus Thalamus: In horizontal sections of brain Lower Higher level level  Thalamus Anterior pole Posterior pole (pulvinar) Medial border Lateral border Inferior border Superior border  Thalamus Relations Anterior pole → head of caudate nucleus, columns of fornix Posterior pole → superior colliculus Lateral → body of caudate nucleus Medial → 3rd ventricle Thalamus has a narrow anterior end called tubercle of thalamus, that lies in the posterior boundary of the interventricular foramen The expanded posterior end, called pulvinar, lies above the superior colliculi Relations Dorsal: lateral ventricle Anterior: interventricular foramen Lateral: Medial: 3rd Internal ventricle capsule Ventral: Subthalamus & Hypothalamus Caudal: midbrain  Surfaces 4 Surfaces: Superior Inferior Medial S Lateral L M l  Superior Surface  Bounded laterally caudate nucleus by caudate stria terminalis nucleus, thalamostriate vein and a nerve fiber bundle called stria terminalis LV  Lateral part lies in the floor of the lateral ventricle & is covered by thalamo- ependyma striate vein  Medial part is related to the choroid plexus of the 3rd ventricle choroid plexus ependyma Between the caudate nucleus & thalamus is the terminal sulcus. In the sulcus runs the thalamostiate vein & stria terminalis Lateral Surface  Related to the internal capsule Inferior Surface  Rests on the subthalamus & hypothalamus  Thalamus Lateral →internal capsule  Medial Surface Stria medullaris thalami  Stria medullaris thalami (a fascicle of nerve fibers) courses along its dorsomedial margin  Below is limited by hypothalamic sulcus  Forms the upper part of the lateral wall of the 3rd ventricle  Covered by ependyma Hypothalamic sulcus Thalamus  Internal Organization Thamalocorfical and  Thalamus is composed of cortico thalamic fibers grey matter, interrupted by are seen with in a white two vertical sheaths of white matter strurure named external medullary matter called medullary lamina. True laminae.  External medullary lamina: ▪ Located laterally, separates reticular nucleus from the rest of the thalamic mass ▪ Contains thalamocortical & corticothalamic fibers  Internal medullary lamina ▪ Y- shaped band, divides thalamus into Anterior, Medial & Lateral nuclear groups ▪ Contains: ▪ Fibers connecting thalamic nuclei with one another ▪ Neuronal collections called intralaminar nuclei Thalamus  Thalamic Nuclei Anterior Part  Ant. thalamic nuclei Medial Part  Dorsomedial nucleus Lateral Part  Dorsal tier  Lateral dorsal nucleus  Lateral posterior nucleus  Pulvinar  Ventral tier  Ventral anterior nucleus  Ventral lateral nucleus  Ventral posterior ( VPL& VPM) Intralaminar Nuclei Midline Nuclei Reticular nucleus Medial Geniculate Body Lateral Geniculate Body Functional classification of thalamic nuclei Specific nuclei  Sensory relay (S-S, visual, auditory)  Motor relay (cerebellum, basal ganglia)  Limbic  Association Non-specific nuclei Thalamus  Lateral Nuclear Group Ventral Tier Ventral anterior Ventral lateral Ventral posterior: (VPL) (VPM) Lateral geniculate Medial geniculate Ventral Anterior Nucleus Influences motor activity Ipsilateral globus pallidus & substantia nigra Motor cortex Premotor & supplementary motor cortex  Ventral Lateral Nucleus Influences motor activity Ipsilateral globus pallidus & substantia nigra Contralateral dentate nucleus Primary motor cortex Primary motor cortex Ventral Posterior Nucleus Chief sensory relay station General sensory afferents from the contralateral half of the Head & neck (VPM) and Body (VPL) Primary somatosensory cortex Lateral Geniculate Body Part of the Visual Pathway Ipsilateral temporal hemiretina Contralateral nasal hemiretina Optic radiation to the primary visual cortex Medial Geniculate Body Part of the Auditory Pathway Inferior colliculus Auditory radiation to the primary auditory cortex  Lateral Nuclear Group Dorsal Tier Lateral Dorsal Lateral Posterior Pulvinar Lateral dorsal nucleus ▪ Part of Limbic System Which part of thalamus is a part of limbic system ? Hippocamus Cingulate gyrus Lateral posterior Pulvinar: Sensory nucleus association cortices of parietal, temporal & sensory association cortex occipital lobes of parietal lobe Medial Nuclear Group Integrates emotion, thought, and judgement Mediodorsal nucleus Hypothalamus, amygdala, other thalamic nuclei, prefrontal cortex Prefrontal cortex & limbic structures  Anterior Nuclear Groups Functionally part of the limbic system. Involved in control of instinctive drives, emotional aspect of behaviour and in memory  3 parts: ▪ Anteroventral ▪ Anteromedial ▪ Anterodorsal Mammillary body of hypothalamus via mammillothalamic tract cingulate gyrus  Midline Nuclei  Located between Brainstem Cingulate medial reticular gyrus and nuclear formation hypothalamus group and the ependyma of 3rd ventricle  Important in visceral functions  Intralaminar Nuclei  Located within the internal medullary lamina  Main nuclei: Centromedian & Parafascicular  Function as activator of the cerebral cortical mantle  Lesions reduce the perception of pain and level of conciousness Reticular formation, spinothalamic & trigeminothalamic systems Widespread regions of cerebral cortex, caudate & putamen of the basal ganglia  Reticular Nucleus Regulates the activity of thalamus  Located between the external medullary lamina & the internal capsule Collaterals of both Thalamocortical & Corticothalamic fibers Other thalamic nuclei  Functions of the thalamus 1. Sensory integration relay station for all sensory pathways (Except olfaction) 2. Capable of recognition of pain, thermal & tactile sensations 3. Influences voluntary movements through basal ganglia & cerebellum – cerebral cortex – cortico-nuclear / cortico-spinal pathways 4. Through ascending activating system – maintains state of wakefulness and alertness 5. Impulses received from hypothalamus projected to prefrontal & cingulate gyrus – Determination of mood 6. Recent memory and emotions 7. Influences electrical activity of cerebral cortex (EEG)  Afferents & Efferents First Order thalamic nucleus High Order thalamic nucleus Subcortical Cortex ↓ ↓ Thalamus Thalamus ↓ ↓ Cortex Cortex Corticothalamocortical Thalamocortical  Nuclei of thalamus First Order thalamic nuclei (FO) Lateral geniculate (LGN) – retina vMedial geniculate (MGN) – inner ear Ventral posterolateral (VPL)- ascending pathways (from the body) Ventral posteromedial (VPM) - ascending pathways (from head & neck) Ventral lateral (VL) –cerebellum Anterior ventral (AV)- mamillothalamic pathways Anterior medial (AM) - mamillothalamic pathways High Order thalamic nuclei (HO) Posterior thalamic (Po) Lateral posterior (LP) Pulvinar (Pu) dMedial geniculate (dMGN) mediodorsal (MD) Parafascicular (Pf) Centrolateral (CL) Centromedial (CM) Intralaminar (IL) Example for first-order Medial lemnicus Retina ↓ ↓ VPL (FO) LGN (FO) ↓ ↓ 321 Cortex 17 Cortex Example for higher-order Sensory cortex (layer V) Prefrontal cortex (V) ↓ ↓ Po (HO) MD (HO) ↓ ↓ Sensory cortex (III, IV) Prefrontal cortex (III, IV)