Parts of the brain Sanjaya Adikari Department of Anatomy Nervous sytem CNS PNS Central Nervous System (CNS) Spinal cord Foramen magnum Skull Vertebral column Meninges Dura mater Arachnoid mater Pia mater Dura mater Arachnoid mater Ventricle Pia mater Ependymal cell.
Download ReportTranscript Parts of the brain Sanjaya Adikari Department of Anatomy Nervous sytem CNS PNS Central Nervous System (CNS) Spinal cord Foramen magnum Skull Vertebral column Meninges Dura mater Arachnoid mater Pia mater Dura mater Arachnoid mater Ventricle Pia mater Ependymal cell.
Parts of the brain Sanjaya Adikari Department of Anatomy Nervous sytem CNS PNS Central Nervous System (CNS) Spinal cord Foramen magnum Skull Vertebral column Meninges Dura mater Arachnoid mater Pia mater Dura mater Arachnoid mater Ventricle Pia mater Ependymal cell layer Main divisions of the brain 1 1 2 3 4 = forebrain + 2 6 5 = midbrain 3 4 6 5 = hindbrain 1 + 2 Cerebrum Diencephalon midbrain 3 pons 4 medulla = brainstem 5 6 Cerebellum Cerebrum 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; • Cerebral hemispheres – Left & right cerebral hemispheres • Diencephalon – Consists of thalamus, hypothalamus etc. Mid-sagittal section of brain Diencephalon thalamus hypothalamus Spinal cord Diencephalon thalamus hypothalamus Spinal cord 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 Falx cerebri Anterior cerebral arteries Dura mater Tentorium cerebelli Corpus callosum 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 Central sulcus Frontal Lobe Parietal Lobe Parietooccipital sulcus Lateral sulcus Temporal Lobe Occipital Lobe Cranial Fossae Main gyri • Precentral gyrus • Postcentral gyrus • Superior/middle/inferior frontal gyri • Superior/middle/inferior temporal gyri • Cingulate gyrus • Parahippocampal gyrus Precentral gyrus Postcentral gyrus Superior, middle, inferior frontal gyri Superior, middle, inferior temporal gyri Cingulate gyrus Parahippocampal gyrus Functional areas of the brain Homunculus Homework • Draw a labelled line diagram to illustrate a midsagittal 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 Lecture II Gray matter and white matter Gray matter White matter • Gray matter consists of nerve cells • White matter consists of nerve fibres Gray matter of the cerebral cortex • Five types of cells are organized into six cortical layers Molecular layer External granular layer External pyramidal layer Internal granular layer Ganglionic layer (Internal pyramidal layer) Multiform layer White matter • Composed of myelinated nerve fibres • Supported by neuroglia • Classified into three groups according to their connections – Commissural fibers – Association fibers – Projection fibers 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 Corpus callosum Body Genu Splenium Rostrum 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 Projection fibers • Afferent and efferent nerve fibers passing to and from the brain stem to the cerebral cortex • Internal capsule, corona radiata, optic radiation Internal capsule and corona radiata Corona radiata Internal capsule Optic radiation Optic tract Cerebral peduncle Pyramidal tract Internal capsule Putamen Cerebral peduncle Amygdala Basal ganglia • Basal ganglia are collection of masses of gray matter within the white matter of cerebral hemispheres Gray matter of cerebral cortex Basal ganglia White matter of cerebrum Basal ganglia…..cont. • Corpus striatum – Divided into two by internal capsule of white matter • Caudate nucleus • Lentiform nucleus (putamen & globus pallidus) • Amygdaloid • Claustrum Basal ganglia…..cont. Thalamus Anterior horn of lateral ventricle Head of caudate nucleus Lentiform nucleus (putamen) Internal capsule Claustrum Lentiform nucleus (globus pallidus) Tail of caudate nucleus External capsule Fiber tracts in the internal capsule Frontopontine Corticobulbar Corticospinal Thalamocortical Parieto/temporo/occipito pontine Visual & auditory Basal ganglia…..cont. • Some definitions include the following also under basal ganglia – Subthalamic nucleus – Substantia nigra Midbrain Diencephalon • Consists of the following – Thalamus – Subthalamus – Hypothalamus – Epithalamus • Habenular nucleus • Pineal gland Corpus callosum Fornix Thalamus Mamillary body Thalamus Epithalamus Subthalamus Hypothalamus Fornix Roof of 3rd ventricle Interthalamic connection Lentiform nucleus Thalamus Internal capsule Hypothalamus Optic chiasma Pituitary Mammillary body 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 Thalamic nuclei 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 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 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 Lecture III Development of the central nervous system Sanjaya Adikari Department of Anatomy Neural tube & cavity Development of brain 1 Prosencephalon (forebrain) 1a 1b 2 Mesencephalon (midbrain) 2 3 Rhombencephalon (hindbrain) 3a 3b 1a 1b Telencephalon Cerebral hemispheres Diencephalon Thalamus, hypothalamus subthalamus, epithalamus 2 3a 3b Midbrain Metencephalon Myelencephalon tectum, tegmentum and cerebral pedunculi pons, upper medulla and cerebellum lower medulla Lateral ventricle Foramen of Monro 3rd ventricle Aqueduct 4th ventricle Central canal of SC Development of spinal cord and brain stem Mantle layer Marginal layer Neuroepithelial layer 1 Neuroblast cells Neurons Neuroepithelial cells 2 Gliablast cells Glial cells Ependymal cells Oligodendroglia Astroglia Microglia Mantle layer Alar plate (sensory) Marginal layer Sulcus limitans Neuroepithelial layer Basal plate (motor) Sensory Motor Posterior horn Lateral horn Sensory Motor Anterior horn SE BE VE VA BA GSA 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 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 Transverse section of midbrain Tectum Tegmentum Crus cerebri or cerebral peduncles Transverse sections of midbrain Superior colliculus Cerebral aqueduct Red nuclues Substantia nigra Cerebral peduncle 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 4th ventricle above 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 4th ventricle above • Laterally are the inferior cerebellar peduncles Motor and sensory decussations of medulla sensory Posterior surface motor Anterior surface Arrangement of cranial nerve nuclei in the flow of the 4th ventricle • Extensive lateral spread of 4th 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 Cerebellum • Lies posterior to the 4th ventricle, pons and medulla • Two cerebellar hemispheres joined by a narrow median vermis • Connected to brain stem by superior, middle and inferior cerebellar peduncles 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 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 Granular cell layer Purkinje cell layer Molecular cell layer Emboliform nucleus Dentate nucleus Middle cerebellar peduncle Function of the cerebellum 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 Limbic system • Functionally important but not well defined anatomically • Surrounds the corpus callosum and the diencephalon • Deals with behaviour, imotion and memory 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 Parts and connecting pathways Ventricular system of the brain 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 Choroid plexus of lateral ventricle Circulation of CSF Arachnoid granulations Foramina of Luschka & Magendie Lecture IV How to draw different sections of the brain stem Posterior surface Anterior surface Main nerve tracts in the spinal cord B A C D G F E 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 Closed medulla at the level of decussation of pyramids Fasciculus gracilis Spinal tract of trigeminal nerve Nucleus gracilis Fasciculus cuneatus Nucleus cuneatus Spinal nucleus of trigeminal nerve Spinal root of the accessory nerve Posterior spinocerebellar tract Central canal Spinothalamic tract Medial longitudinal fasciculus Anterior spinocerebellar tract Decussation of pyramids Pyramid Closed medulla at the level of decussation of medial lemnisci Fasciculus gracilis Spinal tract of trigeminal nerve Nucleus gracilis Fasciculus cuneatus Nucleus cuneatus Spinal nucleus of trigeminal nerve Central canal Medial longitudinal fasciculus Posterior spinocerebellar tract Spinal root of the accessory nerve Spinothalamic tract Decussation of medial lemnisci Anterior spinocerebellar tract Hypoglossal nerve Pyramid Medulla Oblongata at the level of middle of the olivary nuclei Inferior medullary velum Cavity of 4th ventricle Medial longitudinal fasciculus Spinal tract & nucleus of trigeminal nerve Vestibular & cochlear nuclei Inferior cerebellar peduncle Vagus nerve Anterior spinocerebellar tract Reticular formation Spinothalamic tract Olivary nucleus Tectospinal tract Olive Medial lemniscus Pyramid Hypoglossal nerve Pons at the level of facial colliculus Cavity of 4th ventricle Superior medullary velum Medial longitudinal fasciculus Superior cerebellar peduncle Facial colliculus Reticular formation Vestibular nuclei Inferior cerebellar peduncle Spinal lemniscus Spinal tract & nucleus of trigeminal nerve Medial lemniscus Transverse pontine fibres Facial nerve Abducent nerve Corticospinal & corticonuclear fibres Pontine nuclei Midbrain at the level of inferior colliculus Periaqueductal Gray Matter Cerebral aqueduct Trochlear nerve Inferior colliculus Trigeminal lemniscus Mesencephalic nucleus of trigeminal nerve Spinal lemniscus Medial longitudinal fasciculus Medial lemniscus Substantia nigra Reticular formation Cerebral peduncle Interpeduncular fossa Decussation of superior cerebellar peduncles Midbrain at the level of superior colliculus Periaqueductal Gray Matter Cerebral aqueduct Superior colliculus Mesencephalic nucleus of trigeminal nerve Trigeminal lemniscus Spinal lemniscus Medial longitudinal fasciculus Medial lemniscus Substantia nigra Reticular formation Cerebral peduncle Red nucleus Oculomotor nerve Medial longitudinal fasciculus PPRF = Paramedian pontine reticular formation