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Parts of the brain Sanjaya Adikari Department of Anatomy
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Spinal cord Foramen magnum Central Nervous System (CNS)
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Skull Vertebral column
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Meninges Dura mater Arachnoid mater Pia mater
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Dura mater Arachnoid mater Pia mater Ependymal cell layer Ventricle
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1 34 5 6 = forebrain 1 5 4 3 6 2 2 + = midbrain = hindbrain Main divisions of the brain
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1 6 Diencephalon 2 + Cerebellum 43 5 = brainstem midbrain pons medulla Cerebrum
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Cerebral hemispheres –Left & right cerebral hemispheres Diencephalon –Consists of thalamus, hypothalamus etc. Cerebrum is the largest part of the brain. It is situated in the anterior and middle cranial fossae and the whole concavity of the vault of the skull Has two parts;
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Diencephalon thalamus hypothalamus Spinal cord Mid-sagittal section of brain
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Diencephalon thalamus hypothalamus Spinal cord
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Cerebral hemispheres Largest part of the brain Separated by a deep mid-sagittal fisure called longitudinal cerebral fissure The fissure contains the falx cerebri and anterior cerebral arteries Tentorium cerebelli separates cerebral hemispheres from the cerebellum
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Falx cerebri Tentorium cerebelli Dura mater Anterior cerebral arteries Corpus callosum
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Sulci and Gyri To increase the surface area of the brain the cerebral hemispheres are thrown into folds - gyri The gyri are separated from each other by fissures - sulci Hemispheres are divided into lobes (named according to the cranial bones under which they lie) by main sulci –Central –Parieto-occipital –Lateral
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Frontal Lobe Parietal Lobe Occipital Lobe Temporal Lobe Central sulcus Parieto- occipital sulcus Lateral sulcus
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Cranial Fossae
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Main gyri Precentral gyrus Postcentral gyrus Superior/middle/inferior frontal gyri Superior/middle/inferior temporal gyri Cingulate gyrus Parahippocampal gyrus
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Superior, middle, inferior frontal gyri Superior, middle, inferior temporal gyri Precentral gyrusPostcentral gyrus
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Cingulate gyrus Parahippocampal gyrus
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Functional areas of the brain
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Homunculus
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Homework Draw a labelled line diagram to illustrate a mid- sagittal section of the brain including the brain stem. Draw a labelled line diagram to illustrate a horizontal section of the cerebrum through the head of the caudate nucleus. Study the above diagrams before you come for the next lecture on parts of the brain
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Lecture II
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Gray matter and white matter Gray matter White matter Gray matter consists of nerve cells White matter consists of nerve fibres
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Gray matter of the cerebral cortex Five types of cells are organized into six cortical layers
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Molecular layer External granular layer External pyramidal layer Internal granular layer Ganglionic layer (Internal pyramidal layer) Multiform layer
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White matter Composed of myelinated nerve fibres Supported by neuroglia Classified into three groups according to their connections –Commissural fibers –Association fibers –Projection fibers
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Commissural fibers Connects corresponding regions of the two hemispheres Corpus callosum, fornix, anterior and posterior commissures Corpus callosum, the largest commissure of the brain, is divided into rostrum, genu, body and the splenium
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Corpus callosum Genu Rostrum Splenium Body
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Association fibers Connects various cortical regions within the same hemispheres Divided into short and long groups Short association fibers lie immediately beneath the cortex and connect adjacent gyri Long association fibers are arranged into named bundles - fasciculi
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Projection fibers Afferent and efferent nerve fibers passing to and from the brain stem to the cerebral cortex Internal capsule, corona radiata, optic radiation
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Internal capsule Corona radiata Optic radiation Cerebral peduncle Optic tract Pyramidal tract Internal capsule and corona radiata
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Cerebral peduncle Internal capsule Putamen Amygdala
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Basal ganglia Basal ganglia are collection of masses of gray matter within the white matter of cerebral hemispheres Gray matter of cerebral cortex White matter of cerebrum Basal ganglia
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Basal ganglia…..cont. Corpus striatum –Divided into two by internal capsule of white matter Caudate nucleus Lentiform nucleus (putamen & globus pallidus) Amygdaloid Claustrum
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Basal ganglia…..cont.
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Anterior horn of lateral ventricle Head of caudate nucleus Tail of caudate nucleus Thalamus Lentiform nucleus (putamen) Internal capsule Claustrum External capsule Lentiform nucleus (globus pallidus)
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Frontopontine Corticobulbar Corticospinal Thalamocortical Parieto/temporo/occipito pontine Visual & auditory Fiber tracts in the internal capsule
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Basal ganglia…..cont. Some definitions include the following also under basal ganglia –Subthalamic nucleus –Substantia nigra Midbrain
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Diencephalon Consists of the following –Thalamus –Subthalamus –Hypothalamus –Epithalamus Habenular nucleus Pineal gland
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Corpus callosum Fornix Thalamus Mamillary body
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Thalamus Hypothalamus Epithalamus Subthalamus
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Fornix Roof of 3 rd ventricle Interthalamic connection Lentiform nucleus Internal capsule Optic chiasma Pituitary Thalamus Hypothalamus Mammillary body
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Thalamus Large ovoid mass of gray matter Forms large part of diencephalon Very important cell station Receives main sensory tracts (except olfactory pathway) Integrates information it receives and relays to the cerebral cortex and subcortical regions Integrates visceral and somatic functions
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Thalamic nuclei
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Hypothalamus Part of the diencephalon that extends from the optic chiasma to the posterior border of the mammillary bodies Almost all physiological activities of the body are influenced by hypothalamus –Integration of autonomic functions –Regulation of endocrine functions –Maintaining body homiostasis –Regulation of body temperature and body fluids –Sexual behaviour, emosions, drive to eat and drink
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Hypothalamus…. Contains some important cell groups –Supraoptic nucleus –Paraventricular nucleus These have axons running down into the posterior lobe of the pituitary gland Other cell groups deliver their neurosecretions into the hypothalamo-hypophyseal poryal system leading to the anterior lobe of the pituitary gland
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Pineal gland (Pineal body) Projects backwards from the diencephalon to lie posterior to the midbrain Progressive calcification with age becoming visible in x-ray Produces metatonin hormone in a circadian rhythm influenced by light Indirectly controls the function of other endocrine organs, including the pituitary
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Lecture III
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Development of the central nervous system Sanjaya Adikari Department of Anatomy
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Neural tube & cavity
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1 2 3 Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain) 1a 2 3a 1b 3b Development of brain
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1a 2 3a 1b 3b Telencephalon Cerebral hemispheres Diencephalon Midbrain tectum, tegmentum and cerebral pedunculi Metencephalon pons, upper medulla and cerebellum Myelencephalon lower medulla Thalamus, hypothalamus subthalamus, epithalamus
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Lateral ventricle Foramen of Monro Aqueduct 4 th ventricle Central canal of SC 3 rd ventricle
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Development of spinal cord and brain stem Mantle layer Marginal layer Neuroepithelial layer
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Neuroepithelial cells Gliablast cells Neuroblast cells Neurons Glial cells 1 2 OligodendrogliaAstroglia MicrogliaEpendymal cells
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Alar plate (sensory) Basal plate (motor) Sulcus limitans Mantle layer Marginal layer Neuroepithelial layer
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Posterior horn Lateral horn Anterior horn Motor Sensory Motor Sensory
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BE BA SE VE VA GSA
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Brainstem Consists of midbrain, pons and medulla oblongata Broad functions –Conduit for ascending and descending tracts –Contains reflex control centers of respiratory and cardiovascular systems –Associated with control of consciousness –Contains nuclei of cranial nerves III to XII
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Midbrain About 2 cm in length Connects the pons and cerebellum to forebrain by passing through the opening of tentorium cerebelli On the posterior surface are superior and inferior colliculi –SC: centers for visual reflexes. Connected to lateral geniculate body –IC:lower auditory centers. Connected to medial geniculate body On the anterior surface are crus cerebri. Contains cerebral aqueduct Contains cranial nerve nuclei III and IV
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Transverse section of midbrain Tectum Tegmentum Crus cerebri or cerebral peduncles
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Transverse sections of midbrain Cerebral peduncle Cerebral aqueduct Superior colliculus Red nuclues Substantia nigra
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Pons Anterior to the cerebellum Bridges the two hemispheres of the cerebellum On the anterior surface many transverse fibers that go into the middle cerebellar peduncle Basilar groove in the midline anteriorly Motor and sensory roots of trigeminal nerve emerge from anterior surface Posterior surface contains the upper part of the floor of the 4 th ventricle above
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Medulla oblongata Connects to the spinal cord at the level of the foramen magnum, where the first cervical spinal nerve roots start Anterior surface contains the pyramids and the olives Posterior surface contains cuneate and gracile tubercles below and the lower part of the floor of the 4 th ventricle above Laterally are the inferior cerebellar peduncles
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Motor and sensory decussations of medulla sensorymotor Posterior surface Anterior surface
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Arrangement of cranial nerve nuclei in the flow of the 4 th ventricle Extensive lateral spread of 4 th ventricle during embryonic development has caused the alar plates to lie lateral to the basal plates Somatic motor (efferent) nuclei lie closer to the midline and somatic sensory (afferent) nuclei lie away from the midline Visceral nuclei lie in between, with visceral motor more closer and visceral sensory more distant from the midline
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Cerebellum Lies posterior to the 4 th ventricle, pons and medulla Two cerebellar hemispheres joined by a narrow median vermis Connected to brain stem by superior, middle and inferior cerebellar peduncles
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Cerebellum….. Has 3 lobes – anterior, middle and flocculonodular Primary fissure lies between anterior and middle lobes Uvulonodular fissure lies between middle and flocculonodular lobes Horizontal fissure lies within the middle lobe separating superior and inferior surfaces
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Cerebellum…cont. Has an outer cortex of cells. It has 3 layers – granular, purkinje and molecular layers Four intracerebellar nuclei – dentate, emboliform, globose and fastigial Afferent fibers enter through middle and inferior cerebellar peduncles Efferent fibers (axons of purkinje cells) synapse with cerebellar nuclei. Efferents from the nuclei leave through the superior cerebellar peduncle
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Molecular cell layer Purkinje cell layer Granular cell layer
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Dentate nucleus Middle cerebellar peduncle Emboliform nucleus
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Function of the cerebellum
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Cerebellar ataxia Diseases of the lateral cerebellar lobes –Limb ataxia –Gait broad-based and veered towards the side of the lesion Diseases of the cerebellar vermis –Truncal ataxia –Tendency to fall backwards/sideways –No limb ataxia
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Limbic system Functionally important but not well defined anatomically Surrounds the corpus callosum and the diencephalon Deals with behaviour, imotion and memory
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Components of the limbic system Cingulate gyrus Subcallosal gyrus Septal area and olfactory bulb Hippocampal formation –Hippocampal gyrus –Dentate gyrus –Parahippocampal gyrus Amygdaloid body and mammillary body Anterior nucleus of thalamus Hypothalamus
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Parts and connecting pathways
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Ventricular system of the brain
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Formation of CSF 1.Formed mainly in choroid plexus of the ventricles 2.Some is formed from the ependymal cells lining the ventricles and at perivascular spaces Blood-CSF barrier
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Choroid plexus of lateral ventricle
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Circulation of CSF Arachnoid granulations Foramina of Luschka & Magendie
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Functions of CSF 1.Functions as a cushion 2.Serves as a reservoir and regulates the contents of the cranial cavity 3.Nourishment of CNS 4.Way of removal of CNS metabolites 5.Serves as a pathway for pineal secretions to reach the pituitary gland
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Lecture IV
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How to draw different sections of the brain stem
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Anterior surface Posterior surface
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Main nerve tracts in the spinal cord A B G C D E F
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A.Posterior white columns B.Lateral corticospinal tract C.Anterior & posterior spinocerebellar tracts D.Anterior & posterior spinothalamic tracts E.Olivospinal, vestibulospinal, tectospinal tracts F.Anterior corticospinal tract G.Rubrospinal tract
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Closed medulla at the level of decussation of pyramids Fasciculus gracilis Fasciculus cuneatus Nucleus gracilis Nucleus cuneatus Spinal tract of trigeminal nerve Spinal nucleus of trigeminal nerve Decussation of pyramids Pyramid Posterior spinocerebellar tract Anterior spinocerebellar tract Spinothalamic tract Spinal root of the accessory nerve Central canal Medial longitudinal fasciculus
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Closed medulla at the level of decussation of medial lemnisci Fasciculus gracilis Fasciculus cuneatus Nucleus gracilis Nucleus cuneatus Spinal tract of trigeminal nerve Spinal nucleus of trigeminal nerve Decussation of medial lemnisci Pyramid Posterior spinocerebellar tract Anterior spinocerebellar tract Spinothalamic tract Hypoglossal nerve Spinal root of the accessory nerve Central canal Medial longitudinal fasciculus
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Medulla Oblongata at the level of middle of the olivary nuclei Inferior medullary velum Cavity of 4 th ventricle Inferior cerebellar peduncle Vestibular & cochlear nuclei Olivary nucleus Olive Pyramid Anterior spinocerebellar tract Spinothalamic tract Spinal tract & nucleus of trigeminal nerve Vagus nerve Hypoglossal nerve Reticular formation Medial longitudinal fasciculus Tectospinal tract Medial lemniscus
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Pons at the level of facial colliculus Superior medullary velum Cavity of 4 th ventricle Inferior cerebellar peduncle Spinal lemniscus Reticular formation Medial lemniscus Superior cerebellar peduncle Spinal tract & nucleus of trigeminal nerve Medial longitudinal fasciculus Facial colliculus Abducent nerve Facial nerve Pontine nuclei Transverse pontine fibres Corticospinal & corticonuclear fibres Vestibular nuclei
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Midbrain at the level of inferior colliculus Trochlear nerve Inferior colliculus Cerebral aqueduct Medial longitudinal fasciculus Mesencephalic nucleus of trigeminal nerve Trigeminal lemniscus Spinal lemniscus Medial lemniscus Substantia nigra Cerebral peduncle Decussation of superior cerebellar peduncles Interpeduncular fossa Reticular formation Periaqueductal Gray Matter
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Midbrain at the level of superior colliculus Oculomotor nerve Superior colliculus Cerebral aqueduct Medial longitudinal fasciculus Mesencephalic nucleus of trigeminal nerve Trigeminal lemniscus Spinal lemniscus Medial lemniscus Substantia nigra Cerebral peduncle Red nucleus Reticular formation Periaqueductal Gray Matter
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PPRF = Paramedian pontine reticular formation Medial longitudinal fasciculus
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