Nervous System F2024 Students.pdf

Introduction to Nervous System Ashwini Bhat Office- GC 40 C Wing [email protected] Office hours: Mon- Fri 10 am- 12 pm Learning objectives ANT.5: Understand the basic structural components of the nervous system. Given a clinical scenario, description or image, the student should be able t...

Introduction to Nervous System Ashwini Bhat Office- GC 40 C Wing [email protected] Office hours: Mon- Fri 10 am- 12 pm Learning objectives ANT.5: Understand the basic structural components of the nervous system. Given a clinical scenario, description or image, the student should be able to: ANT.5.1. Recognize the organization of the structures that form the nervous system. ANT.5.2. Distinguish the anatomical features of the central nervous system and peripheral nervous system. ANT.5.3. Recognize the formation of the spinal nerve from the ventral and dorsal roots. [email protected]  Textbook readings: 1. Vanderah T. W., and Gould, D. J. (2021). Nolte’s the Human Brain: An Introduction to Its Functional Anatomy. (8th ed.). Philadelphia, PA: Elsevier http://auamed.idm.oclc.org/login?url=https://www.clinicalkey.com/dura/bro wse/bookChapter/3-s2.0-C2018000609X Chapter 1: Introduction to nervous system – entire chapter. 2. Waxman, S. G. (2024). Clinical Neuroanatomy (30th ed.). New York: McGraw- Hill. http://auamed.idm.oclc.org/login?url=https://accessmedicine.mhmedical.com/bo ok.aspx?bookid=3408 Chapter 5: Spinal Cord Sections: Spinal roots and nerves [email protected]  ANT.5.1. Recognize the organization of the structures that form the nervous system.  Nervous system Anatomical subdivision: Central Nervous system (CNS): -brain and spinal cord Peripheral Nervous System(PNS): - Cranial and Spinal nerves - Autonomic nervous system (Sympathetic & Parasympathetic) Fight/Flight Rest/Digest  Autonomic nervous system: Sympathetic-prepares the body for action & stress Fight/Flight Parasympathetic- calms the body & helps to conserve energy Rest/Digest  Structural organization Two types of cells: Neurons/Nerve cells- excitable, functional unit of the nervous system Glial cells/Supporting cells- non-excitable, nonconducting cells  Structure of Neuron Consists of a cell body, processes (axons & dendrites) and synaptic junctions Cell body: contains the nucleus and the organelles that maintain the cell Processes: Dendrites: - short and numerous - bring impulses to the cell body Axon: - single long efferent process -Telodendria- branched ends of axons, often slightly enlarged to form synaptic bulbs  Myelin sheath : ▪ Whitish, fatty (protein-lipoid), segmented sheath around most long axons ▪ Protects the axon ▪ Increases the speed of nerve impulse transmission  Classification of neurons According to polarity: Pseudounipolar (Unipolar)-have one process, the axon that divides close to the cell body into two long axonal branches. Ex: Dorsal root ganglia Bipolar- have one axon and one dendrite. Ex: Retina of the eye Multipolar- have one axon and two or more dendrites. Ex: Motor neurons, interneurons  Sensory Neurons (Afferent Neurons): Classification of neurons convey impulses (sensory information) from peripheral receptors to the CNS. Motor Neurons (Efferent Neurons): convey impulses from the CNS or ganglia (collections of neurons outside the CNS) to target cells (muscles and glands) leading to motor responses. Interneurons (Association Neurons): convey impulses between sensory and motor neurons in the CNS, thus forming integrated networks between cells- account for more than 99% of all neurons in the body.  Non excitable cells Neuroglial cells Insulate and nourish the neurons. Provide structural and functional support to the axons. Neuroglial cells in CNS: Astrocytes Oligodendrocytes Ependymal cells Microglia Neuroglial cells in PNS: Schwan cells/Neurolemmocytes Satellite cells  ANT.5.2. Distinguish the anatomical features of the central nervous system and peripheral nervous system.  CNS organized into Gray matter and White matter Gray matter : areas consisting of cell bodies and dendrites of neurons. White matter: areas consisting of axons of neurons. White matter Gray matter Specific areas of gray matter are often called Nuclei GANGLIA: Clusters of nerve cell bodies in the PNS. NUCLEUS: Clusters of nerve cell bodies in the CNS. Terms associated with White matter Tract-bundle of nerve fibers (axons) that are organized and travel together within the CNS. Ex: ascending & descending tracts Fasciculus mean “bundle” Ex: fasciculus gracilis, fasciculus cuneatus (present in medulla) Lemniscus means “ribbon” Ex: medial & lateral lemniscus Peduncle means “little foot” and is used for a site where axons funnel down into a compact bundle. Ex: middle cerebellar peduncle  Peripheral nerves Nerves arising from brain and the spinal cord Spinal nerves: -31 pairs Cranial nerves: -12 pairs SPINAL NERVES: 31 pairs Cervical – 8 Thoracic -12 Lumbar – 5 Sacral – 5 Coccygeal - 1  Cranial nerves I. Olfactory II. Optic III. Oculomotor IV. Trochlear V. Trigeminal VI. Abducent VII. Facial VIII. Vestibulocochlear IX. Glossopharyngeal X. Vagus XI. Spinal accessary XII. Hypoglossal Autonomic Nervous System Controls the involuntary activities of the body –viscera, smooth muscle, cardiac muscle and glands. Subdivisions: Sympathetic NS: arises from T1 – L2 segments “Thoracolumbar outflow” Parasympathetic NS: from- 3,7, 9, 10th cranial nerves & 2, 3, 4th sacral segments “Cranio-sacral outflow”  Comparison of Somatic NS and Autonomic NS Somatic System : Innervates-Skeletal muscle, tendons, joints Controls voluntary movements involves a single neuron (monosynaptic pathway) that extends from the spinal cord to the skeletal muscle. Autonomic System: Innervates-smooth muscles, cardiac muscles, glands, blood vessels, mucus membranes of internal organs Controls :Heart rate, Respiration, Perspiration, Digestion etc Deals with changes in internal environment (Involuntary) Involves a two-neuron chain (disynaptic pathway) with a pre-ganglionic neuron and a post-ganglionic neuron. The pre-ganglionic neuron extends from the spinal cord to an autonomic ganglion. the post-ganglionic neuron extends from the ganglion to the target organ.  ANT.5.3. Recognize the formation of the spinal nerve from the ventral and dorsal roots.  Spinal nerve: Formation & Branches Arises from spinal cord as a rootlets Dorsal (posterior) root : consisting of sensory fibers (afferent) from cell bodies in posterior root ganglion that extend to the posterior horn of spinal cord Dorsal root (Spinal) ganglion contains cell bodies of sensory neurons. Ventral (Anterior) root contains motor fibers, and it is responsible for carrying efferent (motor) signals from the spinal cord to the muscles. Anterior and posterior roots unite to form Spinal nerve  Emerges through the inter vertebral foramen Divides into dorsal and ventral rami Dorsal ramus- supplies skin and muscles of the back Ventral ramus- supplies skin and muscles of limbs and skin and muscles of antero-lateral body wall, extremities.  Ventral rami form the cervical, brachial, and lumbosacral plexuses. In the thoracic region they remain segmental, as intercostal nerves.  White ramus communicans: part of the sympathetic nervous system, serving as a pathway for preganglionic sympathetic fibers. Myelinated fibers Gray ramus communicans: The gray ramus is part of the sympathetic nervous system and is involved in carrying postganglionic sympathetic fibers. Unmyelinated fibers Dermatome Area of the skin supplied by a segment of spinal cord  [email protected] Ashwini Bhat Office- GC 40 C Wing Office hours: Mon- Fri 10 am- 12 pm