DIENCEPHALON: THALAMUS AND HYPOTHALAMUS
M. O. BUKHARI 1 DIENCEPHALON: General Introduction • Relay & integrative centers between the brainstem & cerebral cortex • Dorsal-posterior structures • Epithalamus • Anterior & posterior paraventricular nuclei • Habenular nuclei – integrate smell & emotions • Pineal gland – monitors diurnal / nocturnal rhythm • Habenular Commissure • Post. Commissure • Stria Medullaris Thalami • Thalamus(Dorsal thalamus) • Metathalamus • Medial geniculate body – auditory relay • Lateral geniculate body – visual relay Hypothalamic sulcus • Ventral-anterior structure • Sub-thalums (Ventral Thalamus) • Sub-thalamic Nucleus • Zona Inserta • Fields of Forel • Hypothalamus
M. O. BUKHARI 2 Introduction THE THALAMUS Location Function External features Size Interthalamic 3 cms length x 1.5 cms breadth adhesion Two ends Anterior end– Tubercle of Thalamus Posterior end– Pulvinar – Overhangs Med & Lat.Gen.Bodies, Sup.Colliculi & their brachia Surfaces Sup. Surface – Lat. Part forms central part of lat. Vent. Med. Part is covered by tela choroidea of 3rd vent. Inf. Surface - Ant. part fused with subthalamus - Post. part free – inf. part of Pulvinar Med. Surface – Greater part of Lat. wall of 3rd ventricle Lat. Surface - Med.boundary of Post. Limb of internal capsule
M. O. BUKHARI 3 Function of the Thalamus
• Sensory relay • ALL sensory information (except smell) • Motor integration • Input from cortex, cerebellum and basal ganglia • Arousal • Part of reticular activating system • Pain modulation • All nociceptive information • Memory & behavior • Lesions are disruptive
M. O. BUKHARI 4 SUBDIVISION OF THALAMUS
M. O. BUKHARI 5 SUBDIVISION OF THALAMUS: WHITE MATTER OF THE THALAMUS
Internal Medullary Stratum Zonale Lamina
External Medullary Lamina
M. O. BUKHARI 6 LATERAL MEDIAL Nuclei of Thalamus Stratum Zonale
Anterior Nucleus Medial Dorsal Lateral Dorsal (Large)
EXT.Med.Lam ILN
Ret.N CMN VPL MGB VPM PVN
Lateral Ventral Medial Ventral LGB (Small) LD, LP, Pulvinar – Dorsal Tier nuclei Hypothalamus VA, VL, VPL, VPM – Ventral Tier nuclei
M. O. BUKHARI 7 VPM Functional group nuclei
1. Specific 2. Non-specific 3. Reticular
1. Specific - Input from certain specific ascending tratcs Project specific cortical areas VPL Ventral tier, Med & Lat. Geniculate bodies
Ventral Posterior Nucleus:
Nucleus Afferent Efferent Relay station VPM Trigeminal lemniscus Post central gyrus Impulses from face & head (3,1 & 2) Taste buds Solitariothalamic tract VPL Medial lemniscus Post central gyrus Exteroception (Pain,Tocuh (3,1 & 2) & Temp) Proprioception Spinal lemniscus from whole body except face & head M. O. BUKHARI 8 Functional group nuclei
Nucleus Afferent Efferent Relay station Ventral Globus pallidus Premotor cortex Striatal impulses anterior (subthalamic fasciculus) area 6 & 8 Ventral Cerebellum Motor & premotor Cerebellar impulses lateral (dentato-rubro-thalamic areas fibres) Area 4 & 6 (Dentato-thalamic fibres) MGB Auditory fibres from Primary auditory Auditory impulses Inferior Colliculus area 41 & 42 LGB Optic tract Primary visual Visual impulses cortex area 17 M. O. BUKHARI 9 Functional group nuclei 2. Non - Specific group Do not receive afferents from ascending Tracts, but have abundant connections with other diencephalic nuclei. Project to cortical association areas in frontal & parietal lobes.
Nucleus Afferent Efferent Relay station Anterior Mamillothalmic tract Cingulate gyrus Attention & Recent nucleus (Mamillary body) memory Medial Other thalamic nuclei & Prefrontal area Mood & Emotional dorsal Hypothalamus balance Lateral Ventral tier of thalamic Precuneus & Integrate sensory dorsal nuclei Cingulate gyrus information Lateral Ventral tier of thalamic Superior parietal Integrate sensory posterior nuclei lobule information Pulvinar Ventral tier of thalamic Association areas Correlates visual & nuclei in parietal, occipital auditory information with & temporal lobes other sensations M. O. BUKHARI 10 Functional group nuclei 3. Reticular nuclei Reticular nucleus, Intralaminar nuclei & Median nuclei (Paraventricular nucleus)
Connected with Reticular formation
Nucleus Afferent Efferent Relay station Reticular Brain stem reticular Whole of cerebral Forms part of reticular formation cortex activating system (RAS) Intralami Brain stem reticular Other thalamic Involved in awareness of nar & formation nuclei & Corpus painful stimuli at thalamic Centro striatum level median M. O. BUKHARI 11 Thalamus: BLOOD SUPPLY
M. O. BUKHARI 12 CONNECTONS OF THE THALAMUS
Main connections of the thalamus. AfferentM. O. BUKHARI fibers are shown on the left, and efferent13 fibers are shown on the right The thalamus is an Prefrontal cortex important relay station Cingulate gyrus Somesthetic sensory area for two sensory-motor (3, 1, 2) axonal loops involving Caudate N. the cerebellum and Hypothalamic Nuclei the basal nuclei: Parietal cortex
The cerebellar- MB Anygdaloid body rubro-thalamic- Inferior parietal lobule
cortical-ponto- Spinal lemniscus Sup. Cereb. Peduncle VPL (Spinothalamic tract) cerebellar loop. RN VPM Trigeminal lemniscus Dentate Nucleus VPL The corticalstriatal- Medial pallidal-thalamic- lemniscus Sup. Sens. N. of Trigeminal NG & NC cortical loop. N. of spinal tract of Trig. nerve
Main Dorsal nerve root
connectionsM. O. BUKHARI 14 of Thalamus Input to the Thalamus
M. O. BUKHARI 15 Input to the Thalamus
Metathalamus Vision and Hearing M. O. BUKHARI 16 Input to the Thalamus
Sensory relay - Ventral posterior group all sensation from body and head, including pain M. O. BUKHARI 17 Input to the Thalamus
Motor control and integration M. O. BUKHARI 18 Input to the Thalamus
Behavior and emotion connection with hypothalamus M. O. BUKHARI 19 Projections from the Thalamus
Metathalamus Vision and Hearing
M. O. BUKHARI 20 Projections from the Thalamus
Sensory relay Ventral posterior group
all sensation from body and head, including pain M. O. BUKHARI 21 Projections from the Thalamus
Motor control and integration
M. O. BUKHARI 22 Projections from the Thalamus
Behavior and emotion connection with hypothalamus
M. O. BUKHARI 23 A Summary of Various Thalamic Nuclei, Their Nervous Connections, and Their Functions Thalamic Nucleus Afferent Neuronal Loop Efferent Neuronal Loop Function Anterior Mammillothalamic tract, Cingulate gyrus, hypothalamus Emotional tone, mechanisms cingulate gyrus, of recent memory hypothalamus Dorsomedial Prefrontal cortex, Prefrontal cortex, Integration of somatic, hypothalamus, other hypothalamus, other thalamic visceral, and olfactory thalamic nuclei nuclei information and relation to emotional feelings and subjective states Lateral dorsal, lateral Cerebral cortex, other Cerebral cortex, other thalamic Unknown posterior, pulvinar thalamic nuclei nuclei
Ventral anterior Reticular formation, Reticular formation, substantia Influences activity of motor substantia nigra, corpus nigra, corpus striatum, cortex striatum, premotor premotor cortex, other cortex, other thalamic thalamic nuclei nuclei Ventral lateral As in ventral anterior nucleus but also major input from Influences motor activity of cerebellum and minor input from red nucleus motor cortex Ventral Trigeminal lemniscus, Primary somatic sensory (areas Relays common sensations to posteromedial gustatory fibers 3, 1, and 2) cortex consciousness (VPM)
Ventral Medial and spinal lemnisci PrimaryM. O. BUKHARI somatic sensory (areas Relays common sensations24 to posterolateral (VPL) 3, 1, and 2) cortex consciousness Thalamic Nucleus Afferent Neuronal Loop Efferent Neuronal Loop Function Intralaminar Reticular formation, To cerebral cortex via Influences levels of spinothalamic and other thalamic nuclei, consciousness and trigeminothalamic tracts corpus striatum alertness Midline Reticular formation Unknown Unknown
Reticular Cerebral cortex, reticular Other thalamic nuclei Known to concerned formation mechanism by which Cerebral cortex regulates thalamus
Medial Inferior colliculus, lateral Auditory radiation to Hearing geniculate lemniscus from both ears superior temporal gyrus body but predominantly the contralateral ear
Lateral Optic tract Optic radiation to visual Visual information geniculate cortex of occipital lobe from opposite field of body vision
M. O. BUKHARI 25 Functions of Thalamus
Sensory integration relay station for all sensory pathways(Except olfaction)
Capable of recognition of pain, thermal & tactile sensations
Influences voluntary movements through basal ganglia & cerebellum – cerebral cortex – cortico-nuclear / cortico-spinal pathways
Through ascending activating system – maintains state of wakefulness and alertness
Impulses received from hypothalamus projected to prefrontal & cingulate gyrus – Determination of mood
Recent memory and emotions
Influences electrical activity of cerebral cortex (EEG)
M. O. BUKHARI 26 LESIONS OF THE THALAMUS
Sensory Loss These lesions usually result from thrombosis or hemorrhage of one of the arteries supplying the thalamus. Damage to the VPM nucleus and the VPL nucleus will result in the loss of all forms of sensation, including light touch, tactile localization and discrimination, and muscle joint sense from the opposite side of the body. Surgical Relief of Pain by Thalamic Cauterization Thalamic Pain Abnormal Involuntary Movements Choreoathetosis with ataxia may follow vascular lesions of the thalamus. It is not certain whether these signs in all cases are due to the loss of function of the thalamus or to involvement of the neighboring caudate and lentiform nuclei. Thalamic Hand
M. O. BUKHARI 27 Fatal familial insomnia a hereditary prion disease in which degeneration of the thalamus occurs, causing the patient to gradually lose his ability to sleep and progressing to a state of total insomnia, which invariably leads to death.
Dejerine–Roussy syndrome or thalamic pain syndrome is a condition developed after a thalamic stroke, a stroke causing damage to the thalamus. The lesions, usually present in one hemisphere of the brain and can lead to dysaesthesia or allodynia
Korsakoff's syndrome is a manifestation of Wernicke's encephalopathy, also called Wernicke's disease. This neurological disorder is caused by a lack of thiamine
(vitamin B1) in the brain, and is also often exacerbated by the neurotoxic effects of alcohol. M. O. BUKHARI 28 Hypothalamus
Located ventral-anterior to thalamus. (Subthalamus, located ventral to thalamus) Form a vital part of the CNS
M. O. BUKHARI 29 Hypothalamus Small (0.3% of the brain) lies in the centre of the limbic system Site of numerous converging & diverging neuronal pathways Controls the ANS & the endocrine system Makes appropriate controlling responses following the integration of its neurons & chemical Coronal view inputs
M. O. BUKHARI 30 STRUCTURAL DESCRIPTION
Extends from the region of optic chiasma to the caudal border of the mammillary bodies Lies below the thalamus Form the floor & the inferior parts of the lateral wall of the 3rd vent. Anterior to the hypothalamus is preoptic area It merges caudally into the tegmentum of the midbrain Its lateral boundary is formed by internal capsule
M. O. BUKHARI 31 Relation
Thalamus M. O. BUKHARI 32 Relation
Optic chiasm M. O. BUKHARI 33 Relation
Pituitary Gland M. O. BUKHARI 34 Relation
Mammillary body: termination of fornix M. O. BUKHARI 35 Relation
Fornix: part of the limbic system M. O. BUKHARI 36 Coronal view
Lateral view
Fornix to mammillary bodies
M. O. BUKHARI 37 Hypothalamic Nuclei Composed of small nerve cells that are arranged in groups or nuclei. Are not clearly segregated from one another The preoptic area is included as part of the hypothalamus The nuclei are divided by an imaginary parasagittal plane into medial and lateral zones M. O. BUKHARI 38 Medial Zone Nuclei Part of the Preoptic Nucleus The Anterior Nucleus, which merges with the Preoptic Nucleus Part of the Suprachiasmatic Nucleus; The Paraventricular Nucleus; The Dorsomedial Nucleus; The Ventromedial Nucleus; The Infundibular (Arcuate) Nucleus; The Posterior Nucleus. M. O. BUKHARI 39 Lateral Zone Nuclei
Part of the preoptic nucleus Part of the suprachiasmatic nucleus The supraoptic nucleus The lateral nucleus The tuberomammillary nucleus The lateral tuberal nuclei.
M. O. BUKHARI 40 CORONAL SECTION OF THE CEREBRAL HEMISPHERES SHOWING THE POSITION OF THE HYPOTHALAMIC NUCLEI.
M. O. BUKHARI 41 REGIONAL LOCATION/CLASSIFICATION OF THE HYPOTHALAMIC NUCLEI (Rostral to caudal) MAMMILLARY
TUBERAL
SUPRACHIASMATIC
PRE-OPTIC
M. O. BUKHARI 42 Pre-Optic Region
Gonadotropic releasing hormone Sexual arousal, appetite, M. O. BUKHARI 43 reproduction Suprachiasmic Region
Secrete ADH, oxytocin Transported via axons to posterior pituitary (hypophysis)
M. O. BUKHARI 44 Regulates thirst
M. O. BUKHARI 45 Body temperature Circadian rhythms
M. O. BUKHARI 46 Tuberal Region
Satiety
M. O. BUKHARI 47 Regulates prolactin and growth hormone β endorphin for pain
M. O. BUKHARI 48 Mammillary region
Limbic system
M. O. BUKHARI 49 Hypocretin (orexin) Lack of orexin= Narcolepsy.
M. O. BUKHARI 50 HYPOTHALAMIC LINES OF COMMUNICATION
Has afferent and efferent connections with the rest of the body via :
a)Nervous connections
b)The bloodstream
c)Cerebrospinal fluid.
M. O. BUKHARI 51 SAGITTAL SECTION OF THE BRAIN SHOWING THE MAIN AFFERENT PATHWAYS ENTERING THE HYPOTHALAMUS.
M. O. BUKHARI 52 The Main Afferent Nervous Connections of the Hypothalamus Pathway Origin Destination Medial and spinal Viscera and somatic structures Hypothalamic nuclei lemnisci, tractus solitarius, reticular formation Visual fibers Retina Suprachiasmatic nucleus Medial forebrain bundle Olfactory mucous membrane Hypothalamic nuclei Auditory fibers Inner ear Hypothalamic nuclei Corticohypothalamic Frontal lobe of cerebral cortex Hypothalamic nuclei fibers Hippocampohypothalami Hippocampus Nuclei of mammillary c fibers; possibly main body output pathway of limbic system Amygdalohypothalamic Amygdaloid complex Hypothalamic nuclei fibers Thalamohypothalamic Dorsomedial and midline nuclei Hypothalamic nuclei fibers of thalamus M. O. BUKHARI 53 Tegmental fibers Tegmentum of midbrain Hypothalamic nuclei SAGITTAL SECTION OF THE BRAIN SHOWING THE MAIN EFFERENT PATHWAYS LEAVING THE HYPOTHALAMUS.
M. O. BUKHARI 54 The Main Efferent Nervous Connections of the Hypothalamus
Pathway Origin Destination Descending fibers in Preoptic, anterior, posterior, and Craniosacral reticular formation to lateral nuclei of hypothalamus parasympathetic and brainstem and spinal thoracolumbar cord sympathetic outflows
Mammillothalamic Nuclei of mammillary body Anterior nucleus of tract thalamus; relayed to cingulate gyrus
Mammillotegmental Nuclei of mammillary body Reticular formation in tract tegmentum of midbrain
Multiple pathways Hypothalamic nuclei Limbic system
M. O. BUKHARI 55 CONNECTIONS OF THE HYPOTHALAMUS WITH THE HYPOPHYSIS CEREBRI Relationship to Pituitary Gland
M. O. BUKHARI 56 Anterior pituitary • Hypophyseal Portal System- Long and short portal blood vessels that connect sinusoids in the median eminence and infundibulum with capillary plexuses in the anterior lobe of the hypophysis • From Pre-optic nucleus • Tubero-infundibular tract to Median eminence, then via Portal veins
M.• O. BUKHARIGonadotropic releasing hormone57 Posterior pituitary • Hypothalamohypophyseal Tract- Nerve fibers that travel from the supraoptic and paraventricular nuclei to the posterior lobe of the hypophysis • Supraoptic-hypophyseal tract • ADH / Vasopressin (supraoptic nuclei) • Oxytocin (paraventricular nuclei)
M. O. BUKHARI 58 Function of the Pituitary
M. O. BUKHARI 59 THE PRESUMED NUCLEAR ORIGIN OF THE HYPOPHYSIS (PITUITARY) RELEASING AND INHIBITORY HORMONES IN THE HYPOTHALAMUS Hypothalamic Regulatory Hormone Presumed Nuclear Origin Growth hormone–releasing Infundibular or arcuate nucleus hormone (GHRH) Growth hormone–inhibiting Suprachiasmatic nucleus hormone (GHIH) or somatostatin Prolactin-releasing hormone ? (PRH) Prolactin-inhibiting hormone ? (PIH) Corticotropin-releasing hormone Paraventricular nuclei (CRH) Thyrotropin-releasing hormone Paraventricular and dorsomedial (TRH) nuclei and adjacent areas Luteinizing hormone–releasing Preoptic and anterior nuclei
hormone (LHRH) M. O. BUKHARI 60 FUNCTIONS OF THE HYPOTHALAMUS Functions of the Main Hypothalamic Nuclei Hypothalamic Nucleus Presumed Function Autonomic Control Supraoptic nucleus Synthesizes vasopressin Endocrine Control (antidiuretic hormone) Neurosecretion Paraventricular nucleus Synthesizes oxytocin Temperature Preoptic and anterior Control parasympathetic nuclei system Regulation Posterior and lateral Control sympathetic system Regulation of Food nuclei and Water Intake Anterior hypothalamic Regulate temperature Emotion and nuclei (response to heat) Behavior Posterior hypothalamic Regulate temperature nuclei (response to cold) Control of Circadian Lateral hypothalamic Initiate eating and increase Rhythms nuclei food intake (hunger center) Medial hypothalamic Inhibit eating and reduce nuclei food intake (satiety center) Lateral hypothalamic Increase water intake (thirst nuclei center) SuprachiasmaticM. O. BUKHARI nucleus Controls circadian rhythms61 CLINICAL CONSIDERATIONS . The hypothalamus should not be interpreted as a structure of little importance. . The connections of the hypothalamus are extremely complicated, and only the major pathways should be committed to memory for use in clinical work. . It is important to remember that an acute lesion is more likely to produce signs and symptoms than is a slowly growing tumor. Obesity and Wasting to the posterior lobe of the Sexual Disorders hypophysis. Hyperthermia and Disturbances of Sleep Hypothermia Emotional Disorders Diabetes Insipidus- lesion of the supraoptic nucleus or from the interruption of the nervous pathway
M. O. BUKHARI 62 END
M. O. BUKHARI 63