Neuroscience 1 - Introduction to the Nervous System PDF

1A NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM DR. A. VIADO M.D....

1A NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM DR. A. VIADO M.D. A. DIVISIONS OF THE NERVOUS SYSTEM OUTLINE I. INTRODUCTION – Nervous System A. Divisions of the Nervous System 1. Central Nervous System 2. Peripheral Nervous System 3. Autonomic Nervous System B. Order of Neuron II. MAJOR DIVISIONS OF THE CENTRAL NERVOUS SYSTEM A. The Brain 1. Brain Development 2. Anatomical Classification 3. Cerebral Hemispheres 4. Gray/White Matter Interface 5. Cerebral Cortex 6. Functional Areas of the Cerebral Cortex 6.1. Sensory Areas 6.2. Motor Areas 6.3. Association Areas 7. Language B. Spinal Cord Main subdivisions: 1.Central Nervous System I. THE NERVOUS SYSTEM -Brain *NB: Brain and Spinal Cord are untransplantable -Spinal cord Amygdala: center of emotions -Protected by the scalp (brain), spine (spinal cord) 2. Peripheral Nervous System -Everything outside the brain and spinal cord.  composed basically of specialized cells, whose function is -Meaning starting the peripheral nerve down the muscles to receive sensory stimuli and to transmit them to effector they innervate organs, whether muscular or glandular -Cranial nerves- innervation of the head- 12  functional unit: Neurons -Spinal nerves- 31 pairs  Neurons: capable of receiving, conducting, and -Basically exposed transmitting impulses to each other as well as to muscle 3. Autonomic Nervous System cells and cells of glands  Subdivided into: Central Nervous System(CNS) 1. CENTRAL NERVOUS SYSTEM Peripheral Nervous System (PNS)  Comprised of the brain and spinal cord suspended in  Sensory input(afferent)-impulse sent toward the brain cerebrospinal fluid (CSF) *monitoring stimuli through receptors  Where correlation and integration of nervous information  Integration- processing of info done between sensory and occur motor stages  Meninges-system of membranes covering the brain and  Motor output(efferent)-impulse sent away from the brain spinal cord *response to stimuli 2. PERIPHERAL NERVOUS SYSTEM  Cranial and spinal nerves  Emanates from and physical extension of the CNS  conduct information to and from the central nervous system 3. AUTONOMIC NERVOUS SYSTEM  innervation of involuntary structures (i.e. heart, smooth muscle, and glands within the body)  distributed throughout the CNS and PNS  Divided into: Sympathetic Nervous System Parasympathetic Nervous System  Sympathetic: fight-or-flight response  Parasympathetic: rest-or-digest Trans 2 | Allida, Andam, Andoy, Brul 1 of 6 NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM  *Enteric Nervous System- involved in regulating the  Further subdivides, each with fluid filled region: ventricle, process of digestion aqueduct or canal B. ORDER OF NEURON ST  1 Order Neuron- Upper Motor Neuron  Brain  Spinal Cord nd  2 Order Neuron- Lower Motor Neuron  Cranial Nerves (12 pairs)  Spinal Nerves (31 pairs) II. MAJOR DIVISIONS OF THE CENTRAL NERVOUS SYSTEM 2. ANATOMICAL CLASSIFICATION A. THE BRAIN  Cerebral hemispheres  composed of an inner core of white matter which is  Diencephalon surrounded by an outer covering of grey matter  Thalamus  subdivided into three major divisions:  Epithalamus  Hindbrain- medulla oblongata, pons, cerebellum  Hypothalamus  Midbrain  Brain Stem  Forebrain- diencephalon, cerebrum  Midbrain  Midbrain- collective term for the medulla  Pons oblongata, pons, and midbrain  Medulla  Cerebellum 1. BRAIN DEVELOPMENT  Spinal Cord st  21 day of development – neural tube is formed Interface in CNS  Neural tube – initially composed of a single layer of -Outer cortex columnar cells, known as neuroepithelial cells 6 layers- cerebral cortex  Proliferation of these cells results in a thickened tubular 4mm layer structure - cephalic region begins to form three -Inner cortex enlargements: the prosencephalon (forebrain), Diencephalon and basal ganglia mesencephalon (midbrain), and rhombencephalon *Dendrites and nerve cell body reside in the cortex (hindbrain) -White matter- composed mainly of fiber tracts or axons  Rostral part of the neural tube – develop into the brain  Rest of neural tube – spinal cord S1T1 2 of 6 NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM  Surface Anatomy  Gyrus- elevated ridges, located at the brain’s entire surface  Sulcus- shallow groove  Fissure- deeper grooves 3. CEREBRAL HEMISPHERES  Central Sulcus( of Rolando)- divides frontal and parieltal lobes  Longitudinal fissure- divides the brain into left and right hemispheres  Lobes- named under bones of the same name *Insula- buried deep in lateral sulcus  Occipital lobe (back of brain)- visual perception  Parietal lobe (top of brain)- sensation  Frontal lobe (front of brain)- thinking/cognition/movement  Temporal lobe (side of brain)- memory, language, emotion  Lateral sulcus- separates temporal lobe from parietal lobe  Parieto-occipital sulcus – divides occipital and parietal lobes but cannot be seen from outside S1T1 3 of 6 NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM 5. CEREBRAL CORTEX  Executive functioning  2-4 nm thick  Transverse cerebral fissure – separates cerebral  No fiber tracts (no axons) hemispheres from cerebellum  Brodmann areas – 52 structurally different areas with assigned numbers  Gray matter – neuron cell bpdies (neurons and neuroglial cells), dendrites, capillaries 6. FUNCTIONAL AREAS OF CEREBRAL CORTEX  Sensory areas: perception  Motor areas: movement  Association areas: integrate diverse information between sensory and motor areas – enable purposeful action  Homunculus – “little man” 4. GRAY/WHITE MATTER INTERFACE  Gray matter - contains neuronal cell bodies, dendrites, glial cells  Six layers composed of neurons  Neurons (pyramidal):  Afferent (sensory)  Efferent (motor) Outer gray- cerebral cortex 6.1 Sensory Areas Inner gray- diencephalon and basal ganglia  Posterior to central sulcus Inner gray and cortex- made up of nerve cell bodies,  Primary somatosensory cortex: postcentral gyrus of dendrites parietal lobe  Allows conscious awareness of sensation  White Matter – contains myelinated axons and myelin-  Ability to localize the sensation producing oligodendrocytes (extend until the peripheral  Somatosensory association area: behind the primary nerves) somatosensory area  Understanding of what is being felt  Special sensory areas  Primary visual cortex (17)  handles information from contralateral retina  if damaged: functionally blind due to lack of conscious awareness of sight  map of visual space  Visual association area (18 and 19) S1T1 4 of 6 NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM  Face recognition usually on the right Motor speech area side  Broca’s Area (44) –specialized motor speech area  Hearing: temporal lobe  Base of precentral gyrus just above lateral sulcus  Primary auditory area(41) in only one hemisphere, usually left  Auditory association area  Word articulation: movement necessary for  Smell( olfactory sense) – located deep in speech temporal lobe along medial surface  If damaged: expressive aphasia – can understand but can’t speak 6.3 Association Areas  Higher-order processing areas  Tie together different kinds of sensory input  Associate new input with memories  Pre-frontal cortex- executive functioning/cognition 6.2 Motor Areas  Anterior to central sulcus  Primary motor area  Precentral gyrus of frontal lobe (4)  Conscious or voluntary movement of  Wernicke’s area- recognizing and understanding spoken skeletal muscles words  Contain large neurons called pyramidal  Junction of parietal and temporal lobes cells (Betz cells)  One hemisphere, usually left  Axons: form massive pyramidal or  Language reception corticospinal tracrs  Fluent aphasia: words are understandable but  These tracts descend through brain stem don’t make sense and spinal cord  Cross to contralateral side in the medulla  Right side of the brain control left side of the body, left side of the brain control right side of the body  Pyramidal System  Tracts of the motor cortex that reach their targets travelling to the spinal cord thru the pyramids of the medulla  Corticospinal tract (Spinal cord- spinal nerves) – movement of muscles below the head with control opposite side of the brain  Corticobulbar tract( Brainstem-nerves) –movement of muscles, control ipsilateral sides of the brain Motor areas  Premotor cortex (6)- complex movements associated with highly processed sensory information 7. LANGUAGE  Frontal eye fields (8)- voluntary movement of the eyes  Motor area: Broca’s area S1T1 5 of 6 NEUROANATOMY INTRODUCTION TO THE NERVOUS SYSTEM  Association area: Wernicke’s area Cervical enlargement  Modification of language and speech - corresponds to cervical plexus which serves motor and  Frontal lobe sensory to upper extremities  Basal ganglia Lumbar enlargement  Cerebellum -Corresponds to lumbar plexus which serves the lower  Pons extremities -end- called conus medullaris  Foramen magnum to lumbar level L1/L2 B. THE SPINAL CORD  Runs through the vertebral canal of the vertebral column Functions:  cylindrical aggregate of nervous tissue 1. Sensory and motor innervation of entire body inferior to the head  white matter surrounds a central cylinder of gray matter through the spinal nerve  ventral horn- region in the spinal cord where neurons 2.Two-way conduction (Motor and Sensory) pathway between the concerned with somatic motor function are located body and the brain (ascending and descending)  lateral horn- axons of the preganglionic sympathetic 3. Major center for reflexes neurons -Fetal 3rd month: ends at coccyx  dorsal horn- location where central processes of unipolar -Birth: ends at L3 neurons of dorsal root ganglia enter the spinal cord via -Adult position at approximately L1- L2 during childhood dorsal rootlets bringing sensory information to the CNS -End: conus medullaris  31 pairs of spinal nerves - leave the spinal cord and pass This tapers into filum terminale of connective tissue, tethered to through intervertebral foramina in the vertebral column coccyx  spinal nerves - named according to the regions of the -Denticulate ligaments: lateral shelves of pia mater anchoring SC to vertebral column with which they are associated dura  8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 -Has also 3 coverings/ potential spaces: dura mater, arachnoid coccygeal mater, pia mater Foramen magnum to lumbar level L1/L2 Spinal cord REFERENCES -begins the spinal cord and ends at the level of L1-L2 1. Snell R.S Clinical Neuroanatomy, 7th Edition 2010. -with 2 enlargements: 2. Dr Allan Viado’s lecture, 2018 S1T1 6 of 6