1. Introduction and Organization of the Nervous System.pdf

INTRODUCTION AND ORGANIZATION OF THE NERVOUS SYSTEM DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Objectives 03 Central and Peripheral Nervous System 04 Organization of the Nervous System 06 Divisions of th...

INTRODUCTION AND ORGANIZATION OF THE NERVOUS SYSTEM DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Objectives 03 Central and Peripheral Nervous System 04 Organization of the Nervous System 06 Divisions of the Central Nervous System 07 The Spinal Cord 08 The Brain 11 The Hindbrain 12 The Midbrain 15 The Forebrain 16 Major Division of the Peripheral Nervous System 20 Early Development of the Nervous System 25 02 OBJECTIVES Understand the basic organization of the main structures that form the nervous system Gain a 3D appreciation of the parts of the brain and their relative position to one another 03  CENTRAL AND PERIPHERAL NERVOUS SYSTEM The nervous system is divided into two main parts: 1. The central nervous system (CNS) = brain and spinal cord 2. The peripheral nervous system (PNS) = cranial and spinal nerves and their associated ganglia Brain and spinal cord: Protected by the skull and vertebral column Covered by a system of membranes, i.e. the meninges Suspended in cerebrospinal fluid (CSF) CNS is composed of neurons Structural and functional units Excitable cells All have the same basic organization consisting of an axon, cell body and dendrites Supported by neuroglia 04 Source: Canva  CENTRAL AND PERIPHERAL NERVOUS SYSTEM CNS internally organized into: White Gray matter = darker in colour and contain nerve cell bodies matter White matter = lighter in colour and contain nerve cell processes (i.e. predominantly axons) In PNS, cranial and spinal nerves conduct information to and from the CNS Gray matter Autonomic Nervous System Innervates the body's involuntary structures (i.e. heart, smooth muscle, and glands) Distributed throughout the CNS and PNS Divided into two parts: Sympathetic division Parasympathetic division Source: http://www.neuroanatomy.ca/coronals.html 05 ORGANIZATION Central Somatic Nervous System (CNS) Nervous System Conducts nerve impulses from CNS to muscles Brain and Spinal Cord Voluntary control Peripheral Autonomic Nervous System (PNS) Nervous System (ANS) Conducts nerve impulses from CNS to organs and Nerves connecting all parts of the body to the brain glands Sensory Division Motor Division Sympathetic Para- Conducts sensory information from Made up of motor fibres that Division sympathetic the sense organs to the CNS conduct nerve impulses from the Activates body during Division CNS to muscles and glands emergency situations "Fight or Flight" Controls non-emergency functions "Rest and Digest" 06 DIVISIONS Cerebral Cortex Forebrain = Cerebrum + Diencephalon Frontal Lobe Higher executive functions, including emotional Midbrain regulation, planning, reasoning and problem-solving. Voluntary movement Hindbrain = Medulla + Pons + Cerebellum (Primary motor cortex) CNS Parietal Lobe Integration of sensory information, including touch, temperature, pressure and pain. Brain Spinal cord (Primary sensory cortex) Temporal Lobe Processing sensory information important for hearing, language recognition and the formation of memories. (Primary auditory cortex) Brainstem Cerebellum Cerebrum Acts as a relay centre Coordination and Major processing centre of the brain. connecting the movement related to associated with reasoning, planning, Occipital Lobe cerebrum and motor skills, especially The major visual processing centre. parts of speech, movement, emotions, cerebellum to the involving the hands and (Primary visual cortex) and problem-solving. Controls spinal cord. It feet. It also helps maintain voluntary muscle movements. performs many posture, balance, and Limbic Lobe automatic functions equilibrium. Motivationally driven and emotional behaviours, such as breathing, memory, homeostatic responses, and sexual heart rate, body behaviour. temperature, wake and sleep cycles, Diencephalon Cerebral Hemispheres digestion, sneezing, Acts as a primary relay and Insular Lobe coughing, vomiting, processing centre for Sensory processing (interoception), motor control, and swallowing. sensory information and self-awareness, decision making, homeostasis, Midbrain autonomic control. Basal Ganglia emotions, conscious desires. Pons Thalamus Primarily responsible for motor control, as well as other roles Medulla Hypothalamus such as motor learning, Subthalamus executive functions, emotional Epithalamus behaviours, and play an Hippocampus and Amygdala important role in reward and reinforcement, addictive behaviours and habit formation Caudate Nucleus Putamen Globus Pallidus 07  THE SPINAL CORD Situated within the vertebral canal Surrounded by 3 meninges 1. Dura mater 2. Arachnoid mater 3. Pia mater Further protection provided by CSF located within the subarachnoid space Roughly cylindrical Begins superiorly at the foramen magnum, where it is continuous with the medulla oblongata Terminates inferiorly in the lumbar region Pia mater Tapers off into the conus medullaris Filum terminale descends from the apex to Source: Canva Arachnoid mater attach to the back of the coccyx Dura mater 08  Rootlets Posterior root Anterior root THE SPINAL CORD Spinal nerve 31 pairs of spinal nerves attached by anterior (motor) roots and posterior (sensory) roots DRG Each root is attached to the cord by series of rootlets, which extend the whole length of the corresponding segment of the cord Each posterior root possess a posterior (dorsal) root ganglion (DRG) Cells of DRG give rise to peripheral and central nerve fibres (i.e. axons) Ganglion = collection of nerve cell bodies located outside the CNS Source: Canva 09  Posterior horn THE SPINAL CORD Central canal Gray commissure PWC Structure Inner core of gray matter surrounded by white matter Gray matter = H-shaped in cross-section White Gray Anterior and posterior gray columns (horns) matter matter LWC Gray commissure connects the horns Small central canal located within the gray commissure White matter is divided into: AWC Anterior white column (AWC) Lateral white column (LWC) Posterior white column (PWC) Source: Canva Anterior horn 10 THE BRAIN Located in the cranial cavity Continuous with spinal cord through the foramen magnum Surrounded by meninges: Dura mater (outermost layer) Arachnoid mater (middle layer) Pia mater (innermost layer) Cranial and spinal meninges are continuous with one Forebrain another Divided into three major divisions: 1. Hindbrain Midbrain 2. Midbrain 3. Forebrain The brainstem is a collective term for the: Hindbrain Medulla oblongata Pons Midbrain 11 Source: https://pathshalanepal.com/question/give-the-functions-of-different-parts-of-the-brain/  THE HINDBRAIN Medulla oblangata Conical in shape Midbrain Connects the pons superiorly to the spinal cord inferiorly Contain collections of neurons = nuclei Serve as a conduit for ascending and descending nerve fibres Pons Pons Located on the anterior surface of the cerebellum, inferior to the midbrain and superior to the medulla oblongata Contain a large number of transverse fibres connecting Medulla the two cerebral hemispheres Contain: Many nuclei Ascending and descending nerve fibres Source: https://sites.uclouvain.be/braininteratlas/enl 12  THE HINDBRAIN Cerebellum Lies in the posterior cranial fossa Located posterior to the pons and medulla oblongata Two laterally placed hemispheres connected by vermis Connected to: Midbrain via superior cerebellar peduncles Medulla oblongata via inferior cerebellar peduncles Peduncles = large bundles of nerve fibres Surface layer = cortex Gray matter Highly folded (folia) Folia separated by closely set transverse fissures White matter located deep to gray matter Contain masses of gray matter (nuclei) Largest of the nuclei = the dentate nucleus 13 Source: https://sites.uclouvain.be/braininteratlas/enl  THE HINDBRAIN 4th Ventricle CSF filled cavity Surrounded by the medulla oblongata, pons and cerebellum Connected superiorly to the 3rd ventricle via the cerebral aqueduct Continuous inferiorly with the central canal of the spinal cord Communicates with the subarachnoid space via three openings located in the inferior part of the roof 1x Median aperture (foramen of Magendie) 2x Lateral apertures (foramen of Luscha) Source: https://sites.uclouvain.be/braininteratlas/enl 14 Diencephalon CA Midbrain THE MIDBRAIN Cerebellum Narrow part of brain Connects the forebrain to the hindbrain Pons 4V Cerebral aqueduct (CA) Narrow cavity Connects the 3rd and 4th ventricles Contain many nuclei Ascending and descending nerve fibres Medulla Source: https://sites.uclouvain.be/braininteratlas/enl 15 THE FOREBRAIN Diencephalon Consist of: Dorsal thalamus Ventral thalamus Dorsal thalamus 3V Large egg-shape mass of grey matter on either side of the third ventricle Thalamus The anterior end of the thalamus forms the Hypo- posterior boundary of the interventricular thalamus foramen Hypothalamus form the lower part of the lateral wall of the 3rd ventricle Source: https://sites.uclouvain.be/braininteratlas/enl 16 THE FOREBRAIN Cerebrum The largest part of the brain Two hemispheres connected by the corpus callosum (white matter) Extends from frontal to occipital bones of the skull, superior to the anterior and middle Cerebral cranial fossae hemisphere Located above the tentorium cerebelli posteriorly The hemispheres are separated by a deep cleft, longitudinal fissure Falx cerebri projects into the longitudinal fissure Longitudinal fissure Source: https://sites.uclouvain.be/braininteratlas/enl 17 THE FOREBRAIN Parietal lobe Cerebrum The surface layer of each hemisphere = cortex Frontal Composed of gray matter lobe Highly folded Occipital Increases the surface area of the cortex lobe Gyri (singular: gyrus) = folds Temporal Sulci (singular: sulcus) = grooves located between lobe the gyri Fissures = deep sulci Large sulci (fissures) subdivide the surface of each hemisphere into lobes Lobes of the brain are names according to bones of the cranium under which they lie Fissure Gyrus Sulcus Source: https://sites.uclouvain.be/braininteratlas/enl 18 THE FOREBRAIN Caudate n. Lentiform n. Cerebrum Each hemisphere contain, below the cortex, a central core of white matter White Gray matter Several large masses of gray matter are located within the white matter matter = basal nuclei (ganglia) Corona radiata Fan-shaped collection of nerve fibres Runs in the white matter to and from the cortex to the brainstem Converges on the basal nuclei and pass between them as the internal capsule Caudate nucleus = medial to internal capsule Lentiform nucleus (globus pallidus + putamen) = lateral to internal capsule 3rd ventricle Lateral ventricle Lateral ventricle = CSF filled cavity located within each hemisphere Communicates with the 3rd ventricle via the interventricular Internal capsule foramina Source: http://www.neuroanatomy.ca/coronals.html 19  MAJOR DIVISIONS OF THE PERIPHERAL NERVOUS SYSTEM Cranial and Spinal Nerves Consist of bundles of nerve fibres supported by connective tissue 12 pairs of cranial nerves leave the brain and pass through foramina in the skull 31 pairs of spinal nerves leave the spinal cord and pass through the intervertebral foramina in the vertebral column Spinal nerves are associated with regions of the spinal cord: 8 cervical (but only 7 cervical vertebrae) 12 thoracic 5 lumbar 5 sacral 1 coccygeal (but 4 coccygeal vertebrae) Source: https://teachmeanatomy.info/head/cranial-nerves/summary/l 20 Spinal nerve MAJOR DIVISIONS OF THE DRG PERIPHERAL NERVOUS SYSTEM Spinal Nerves Connected to spinal cord by two roots: Anterior (ventral) root Consist of bundle of nerve fibres that carry nerve impulses away from the CNS Efferent fibres Fibres going to skeletal muscle and cause contraction = motor fibres Neuron cell bodies of these fibres are located in the anterior gray horn of the spinal cord Posterior (dorsal) root Consists of bundles of nerve fibres that carry nerve impulses to the CNS Afferent fibres Fibres carry information about sensations of touch, pain temperature, and vibration = sensory fibres Neuron cell bodies of these fibres are located in a swelling on the posterior root = posterior (dorsal) root ganglia (DRG) Spinal nerve roots pass from the spinal cord to the level of their respective intervertebral foramina, where they unite to form a spinal nerve Anterior root Spinal nerve contains a mix of both motor and sensory fibres Posterior root 21 Source: Canva  MAJOR DIVISIONS OF THE Cervical PERIPHERAL NERVOUS SYSTEM Spinal Nerves Disproportionate growth in length of the vertebral column compared to that of the spinal cord during development Thoracic Conus medularis Lenght of the spinal roots increases progressively from superior to inferior: In the upper cervical region = roots are short and run almost horizontally L1 In the lumbar and sacral regions below the level of termination of the spinal cord (i.e. lower border of L1 in adult) = roots form a vertical leash of nerves around the filum terminale Lower nerve roots collectively referred to as the cauda equina Filum terminale S1 Cauda equina 22 Source: https://sites.uclouvain.be/braininteratlas/enl  MAJOR DIVISIONS OF THE PERIPHERAL NERVOUS SYSTEM Spinal Nerves Each spinal nerve divides into large anterior and smaller posterior ramus after emerging from the intervertebral foramen Each ramus contain both motor and sensory fibres Posterior ramus Pass posteriorly around the vertebral column Supply muscle of the skin and back Anterior ramus Pass anteriorly Supply the muscles and skin over the anterolateral body wall and all muscles and skin of the limbs Anterior rami join one another at the root of the limbs to form complicated nerve plexuses Cervical and brachial plexuses are located at the root of the upper limbs Source: https://slideplayer.com/slide/771641/ Lumbar and sacral plexuses are located at the root of the lower limbs 23  MAJOR DIVISIONS OF THE PERIPHERAL NERVOUS SYSTEM Sensory ganglia Fusiform swellings on the posterior root of each spinal nerve, proximal to the root's junction with a corresponding anterior root Referred to as posterior (dorsal) root ganglia Similar ganglia found along the course of cranial nerves (CNs) V, VII, VII, IX, and X Constitute the sensory ganglia of these CNs Autonomic ganglia Source: Canva Irregular in shape Located along the course of efferent nerve fibres of the ANS Paravertebral sympathetic chains around the roots of the great visceral arteries in the abdomen Close to, or embedded within the walls of various viscera 24  EARLY DEVELOPMENT OF THE NERVOUS SYSTEM Before the formation of the nervous system in the embryo 3 main cell layers differentiate Endoderm Innermost cell layer Gives ride to the GIT, lungs and liver Mesoderm Middle cell layer Gives rise to muscle, connective tissue and vascular system Ectoderm Outermost layer Composed of columnar epithelium Gives rise to the entire nervous system Source: https://clinicalgate.com/development-of-the-brain/ 25  EARLY DEVELOPMENT OF THE NERVOUS SYSTEM 3rd week of development 1. Ectoderm on the dorsal surface of the embryo between the primitive knot and buccopharyngeal membrane thickens and give rise to the neural plate 2. The neural plate develops a longitudinal groove = neural groove 3. Groove deepens and bounded on either side by the neural folds 4. With further development the neural folds fuse = neural tube 5. Fusion starts at the midpoint along the neural groove and extends cranially and caudally Cavity of the neural tube remains in communication with the amniotic cavity during early development via the anterior and posterior neuropores 6. Anterior neuropore closes first and two days later the posterior neuropore closes Neural tube closure is usually complete within 28 days Source: https://clinicalgate.com/development-of-the-brain/ 26  EARLY DEVELOPMENT OF THE NERVOUS SYSTEM Neural crest cells A strip of ectodermal cells that bud off from the lateral margins of the neural plate during the formation of the neural tube Located between the neural tube and surface ectoderm Eventually migrate ventrolaterally on each side of the neural tube Will differentiate into cells of: Posterior root ganglia Sensory ganglia of the cranial nerves Autonomic ganglia Cells of the suprarenal medulla Melanocytes Potentially also give rise to mesenchymal cells in the head and neck Source: https://clinicalgate.com/neural-crest// 27 EARLY DEVELOPMENT OF THE NERVOUS SYSTEM Brain vesicles Proliferation of cells at the cephalic end of neural tube cause it to dilate and form three primary brain vesicles: Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain) The rest of the neural tube elongates and remain smaller in diameter and will give rise to the spinal cord Source: https://www.drawittoknowit.com/course/embryology/glossary/developmental-process/brain-vesicles Primary vesicle Secondary vesicle Adult derivate Telencephalon Cerebral hemispheres, basal ganglia, hippocampus Prosencephalon Diencephalon Thalamus, hypothalamus, pineal body, infindibulum Mesencephalon Mesencephalon Midbrain (tectum, tegmentum, crus cerebri) Metencephalon Pons, cerebellum Rhombencephalon Myelencephalon Medulla oblongata 28  THANK YOU FOR YOUR ATTENTION Content for this lecture: Chapter 1 | Snell's Clinical Neuroanatomy, 8th Edition