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Thalamus and Limbic System

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Thalamus and Limbic System Thalamus and Limbic System Neuroanatomy block-Anatomy-Lecture 18 Editing file Objectives At the end of the lecture, students should be able to: ● Describe the anatomy and main functions of the thalamus. ● Name and identify different nuclei of the thalamus. ● Describe the main connections and functions of thalamic nuclei. ● Name and identify different parts of the limbic system. ● Describe main functions of the limbic system. ● Describe the effects of lesions of the limbic system. Color guide ● Only in boys slides in Green ● Only in girls slides in Purple ● important in Red ● Notes in Grey Thalamus ● It is the largest nuclear mass of the whole body. ● It is the largest part of the diencephalon. ● It is formed of two oval masses of grey matter. ● It is the gateway to the cortex. ● Together with the hypothalamus they form the lateral wall of the 3rd ventricle. ● It sends received information to the cerebral cortex from different brain regions. ● Axons from every sensory system (except olfaction) synapse in the thalamus as the last relay site ‘’Last Pit Stop’’ before the information reaches the cerebral cortex. ● Resemble a small hen. There are some thalamic nuclei that receive input from: 1 Cerebellar nuclei Basal ganglia 2 3 Limbic-related brain regions 3 Relations of the Thalamus It has 4 surfaces and 2 ends : Surfaces Lateral Medial Superior\Dorsal Inferior\ ventral Posterior limb of the The 3rd ventricle. Lateral ventricle Hypothalamus Anteriorly internal capsule. In some people the 2 thalami are and fornix. & Subthalamus posteriorly. connected to each other by interthalamic adhesion (connexus,) or Massa. intermedia, which crosses through the 3rd ventricle. Ends Anterior Posterior Forms a projection, called the anterior tubercle. Broad and forms a projection called the Pulvinar which It lies just behind the inter-ventricular foramen. lies above the superior colliculus and the lateral & medial Geniculate bodies. 4 Internal Structure of the Thalamus White matter: External medullary lamina: ● Covers the lateral surface. ● It consists of thalamocortical and corticothalamic fibers. Internal medullary lamina: ● Bundle of Y-shaped myelinated (afferent and efferent) fibers. ● It divides the thalamus into 3 nuclear groups: 1. Anterior 2. Medial 3. Lateral ● Each is subdivided into a number of named nuclei. Lateral Nuclear Group It is divided into Dorsal and Ventral tiers: Dorsal tier: Ventral tier: which contains; 1. Ventral Anterior (VA) 1. Lateral Dorsal (LD) 2. Ventral Lateral (VL) 2. Lateral Posterior (LP) 3. Ventral Intermediate (VI) 3. Pulvinar (PUL) 4. Ventral Posterior (VP) (PLVNT, PMVNT) 5. Medial & Lateral geniculate bodies or nuclei. 5 Projection of thalamic Nuclei Nuclear Group Afferent Efferent Cingulate Anterior Thalamic Nucleus Mamillary body gyrus(limbic system) Prefrontal/ Frontal Medial Nucleus Hypothalamus cortex Globus pallidus body and Ventral Anterior Nucleus Premotor cortex substantia nigra Primary motor Ventral Lateral Nucleus Dentate nucleus cortex Ventral posterior Lateral Nucleus Medial and spinal leminisci Sensory cortex Ventral Posterior Medial Nucleus Trigeminal leminiscus Sensory cortex Lateral Geniculate Nucleus Optic tract Visual cortex Medial Geniculate Nucleus Lateral Leminiscus Auditory cortex 6 Limbic system ● Limbic from ” Limbus” in Latin,means “border or edge”. It separates the medial surface of It consists of a number of cortical & subcortical the cerebral cortex from the Limbic system structures with looped connections that all project to diencephalon the hypothalamus (particularly mammillary bodies.) Functions of limbic system Emotions: emotional response,behaviour Visceral & Motor responses Motivation Memory 5 Olfaction & Mood (happy, cry, laugh, sad, afraid, 2 3 4 involved in(sex,pleasure,hunger) 1 aggression, depression) Structures of Limbic system 4 Septal area 1 Limbic cortex (Lobe) 2 Hippocampus 3 Amygdala ❖ These structures form connections between the limbic system and the hypothalamus, thalamus and cerebral cortex. ❖ The hippocampus is important in memory and learning, while the limbic system itself is important in the control of the emotional responses. ❖ Cortical structure : 1-Limbic lobe. 2-Hippocampal formation. 3-Septal areas. 4-Prefrontal area (Olfactory cortex). 7 Structures of Limbic system 1 Limbic cortex (Lobe) 2 Hippocampus ❖ involved in: Formation, Organization, and Storing of memories (FOS of memories) ● C-shaped ring of grey matter on the It is important in forming new memories and connecting emotions and senses, such as smell and sound, to memories. medial side of each cerebral hemisphere, surrounding the corpus ❖ It is a horseshoe paired structure, one in each cerebral hemisphere. It acts as a memory callosum indexer by sending memories to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them when necessary. ● It includes: ❖ Site: It is a scrolled(infolding) structure in the inferomedial part of the temporal lobe 1. Subcallosal area ❖ Function: 2. Cingulate gyrus ● Memory (file new memories as they occur). 3. Isthmus (behind splenium of ● The hippocampus & its connections are necessary for consolidation of new corpus callosum) short-term memories. 4. Parahippocampal gyrus ● its principal efferent pathway is called the FORNIX 5. Uncus. ❖ Fornix: It is C-shaped group of fibers connecting the hippocampus with mammillary body(and then to the anterior nuclei of thalamus) ➔ It consist of: 2 Fimbria 2 Crus 1 Body 2 Column ➔ The Fornix is an important component of PAPEZ CIRCUIT (based on connecting the hypothalamus with limbic lobe to control emotions ) (is a neural circuit for the control of emotional expression) 8 Structures of Limbic system 3 Amygdala 4 Septal nuclei ❖ Site: It almond shaped mass of nuclei that lies near the temporal pole (deep within the temporal lobes)close to the tail of the caudate nucleus. ❖ Site: Located anterior to the interventricular ❖ Function: It is involved in septum (septum pellucidum) and ❖ 1. FEAR anterior to hypothalamus. 2. Emotions ❖ 3. Anger, Aggression Function: It is the pleasure zone. 4. Release of Hormonal. ❖ Main connections: ❖ CONNECTIONS OF AMYGDALA 1. To Hypothalamus. ❖ Inputs: Association areas of visual, auditory & somatosensory cortices. 2. To Habenular nuclei (lies in epithalamus of ❖ Outputs: Hypothalamus & Autonomic nuclei in the brain stem. diencephalon) ❖ Lesion: ➢ Lack of emotional responses ➢ docility (reduced emotional expression). 9 Lesions associated with limbic lobe disorders Korsakoff’s psychosis Temporal lobe epilepsy Alzheimer’s disease Schizophrenia A chronic memory disorder caused the hippocampus is one of by severe deficiency of thiamine The hippocampus is a common focus the first brain areas to mental disorder with (vitamin B-1) & alcoholic site in epilepsy, and can be damaged show damage in abnormal behavior + through chronic seizures. intoxication. Alzheimer’s disease inappropriate actions Patient has anterograde and feelings It is sometimes damaged in diseases Inability to remember recent such as herpes encephalitis amnesia”= inability to gain events and long-term memory gaps and retain new memories. “Retrograde” = loss of retained old memories occurred before the injury & “anterograde amnesia”= inability to gain new memories. 10 Practice Q5: The efferent of the ventral anterior nucleus goes to? Q1: Which one of these is NOT cortical structure? A. Somatosensory area A. Septal areas B. Sensory cortex B. Limbic lobe. C.Premotor cortex C. Amygdala D. Auditory cortex D. Hippocampal formation Q6: Which of the following is a part of the dorsal tier of the lateral nuclear Q2: Which area is responsible for pleasure? group? A.Septal area A.Ventral intermediate B. Limbic cortex B.Ventral posterior C.Amygdala C.Lateral posterior D.Hippocampus D.Medial geniculate nuclei Q3: FORNIX connects? Q7: What is anterograde amnesia? A. Hippocampus with fimbria A.The inability to make new memories B. Mammillary body with fimbria B. The inability to retain old memories C. Mammillary body with cingulate gyrus C . The inability to retain new memories D. Hippocampus with mammillary D. A & C Q4: what is true about the amygdala? Q8 : Which one of these is not a function of the limbic system? A. Close to the tail of the caudate nucleus A. Memory B. Lies far away from the temporal pole B. Feeling C. Almond shaped mass C. Behavior D. A and c D. Pleasure Answers: Q1(C) Q2(A) Q3(D) Q4(D) Q5(C) Q6(C) Q7(D) Q8(B) 11 Members board Team leaders ● Abdulrahman Shadid ● Ateen Almutairi Girls team : Boys team: ● Ajeed Al Rashoud ● Mohammed Al-huqbani ● Taif Alotaibi ● Salman Alagla ● Noura Al Turki ● Ziyad Al-jofan ● Amirah Al-Zahrani ● Ali Aldawood ● Alhanouf Al-haluli ● Khalid Nagshabandi ● Sara Al-Abdulkarem ● Omar Alammari ● Renad Al Haqbani ● Sameh nuser ● Nouf Al Humaidhi ● Abdullah Basamh ● Jude Al Khalifah ● Alwaleed Alsaleh ● Nouf Al Hussaini ● Mohaned Makkawi ● Rahaf Al Shabri ● Abdullah Alghamdi ● Danah Al Halees ● Very secret lecture reviewer ● Rema Al Mutawa ● Amirah Al Dakhilallah ● Maha Al Nahdi Contact us: ● Razan Al zohaifi ● Ghalia Alnufaei Editing file most probably you don't need this .
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