University of Northern Philippines Spinal Nerves PDF

UNIVERSITY OF NORTHERN PHILIPPINES NEUROSCIENCE 1A LC16 Spinal Nerves COLLEGE OF MEDICINE,...

UNIVERSITY OF NORTHERN PHILIPPINES NEUROSCIENCE 1A LC16 Spinal Nerves COLLEGE OF MEDICINE, BATCH 2026 Transcribers and Editors: Dr. Allan Viado | Dec. 2022 Samillano, Sanga, Santos, Segovia, Servito, Somera SPINAL NERVES I. INTRODUCTION A. Ganglia B. Nerves C. Neuroregeneration D. Gross Anatomy of Spinal Nerves i. Spinal Nerve Segments and Herniations II. RAMIS AND CERVIAL PLEXUS III. BRACHIAL PLEXUS AND ITS TERMINAL BRANCHES IV. LUMBAR PLEXUS V. SACRAL PLEXUS VI. DERMATOMES VS. MYOTOMES Figure 2. Schematic representation of dorsal root ganglia. I. INTRODUCTION Figure 3. The Trigeminal Ganglia of Figure 4. Spinal Ganglion Stained With the CN V. H&E. 2. Autonomic ganglia (cell bodies of postganglionicautonomic nerves) - Multipolar neurons enveloped by satellite cells (Capsular Cells) - Some are Intramural (within certain organs) - Sympathetic/parasympathetic ganglia - Example: Paravertebral ganglion Part of sympathetic tract, found on the thoracic and upper lumbar segments of the spinal cord The spinal nerve will have a Rami Communicantes (communicating fibers that runs through autonomic ganglia Figure 1. Overview of the CNS and PNS. PERIPHERAL NERVOUS SYSTEM - Part of the Nervous system that consists of nerves (Cranial andSpinal) and their ganglia outside of the Brain and Spinal Cord - Main components: Ganglia Nerves (Cranial/Spinal/Peripheral) Nerve endings A. GANGLIA - Ovoid structure containing neuronal cell bodies (with theirdendrites), glial cells, supported by connective tissues. - Relay stations to transmit impulses (sensory andautonomic) - GANGLIA vs NUCLEI Ganglia – nerve cell bodies in the PNS, supported byconnective tissues Nuclei – nerve cell bodies in the CNS, NOT supportedby connective tissues Figure 5. The Paravertebral Ganglion (Autonomic Ganglion). ▪ Types of Ganglia 1. Sensory Ganglia (cell bodies of sensory neurons) - Unipolar/pseudounipolar cell bodies enveloped bycuboidal cells - Examples: Spinal Ganglia: Dorsal Root Ganglia is made up of pseudounipolar sensory neurons Cranial Nerve Sensory Ganglia - e.g., Trigeminal ganglia/Semilunar Ganglion: supports the 3 divisions of Trigeminal nerve Figure 6. Cells of autonomic (sympathetic) ganglion. [NEUROSCIENCE1A]-01.16-Spinal Nerves– Dr. Allan Viado B. NERVES MYELINATED NEURONS UNMYELINATED NEURONS Myelinated neurons fibers contain the Unmyelinated neurons fibers do not ▪ CRANIAL NERVES myelin sheath. have the myelin sheath. - 12 pairs The Schwann cells wrap tightly around The Schwann cells are not wrap tightly - purely sensory the nerve axon and form the myelin around the nerve axon and simply form - purely motor sheath. a groove. - Mixed motor and sensory (Sensorimotor) The axis cylinder of the myelinated The axis cylinder of the myelinated nerve fibers has two sheats. nerve fibers has one sheats. ▪ SPINAL/ PERIPHERAL NERVES The speed of transfer of nerve The speed of transfer of nerve impulses - Bundles of nerve fibers (axons) outside the CNS (once the axonsemerge impulses through myelinated nerve through unmyelinated nerve fibers is outside the CNS, they bundle to form nerves) fibers is much faster when compared much slower. - Surrounded by connective tissue (as compared to the axons of the to unmyelinated. CNS, the tracts, which are not surrounded by connective tissue) Myelinated nerve fibers appear as Unmyelinated nerve fibers appear as - Carries both sensory and motor fibers (Sensorimotor) white in the fresh state. grey in the fresh state. Myelinated fibers show nodes and Unmyelinated fibers do not show nodes internodes. and internodes. Myelinated fibers possess nodes of Unmyelinated fibers do not possess Ranvier. nodes of Ranvier Myelinated nerve fibers occur in the Unmyelinated nerve fibers occur in the white matter of the brain, spinal cord autonomic nervous system. and in the central and cranial nervous system. Myelinated nerve fibers may give off Collateral nerve fibers are not produced collateral nerve fibers. in unmyelinated nerves. Figure 7. Scanning electron micrograph of a cross- section of a peripheral nerve Figure 10. Differences between Myelinated and UnmyelinatedNeurons. showing individual axons surrounded by myelin sheaths. Sensitivity Diameter Mystification Conduction Fiber Type Function to nerve ▪ NERVE FIBERS (microns) (Myelination) velocity block - Axons enveloped by sheaths of connective tissue Type A - Grouped together constitute the nerve Proprioception, Alpha(α) 12-20 heavy 70-120 + - Types: (1) Myelinated and (2) Unmyelinated motor Touch, Beta(β) 5-12 Heavy 30-70 ++ pressure MYELINATED FIBERS UNMYELINATED FIBERS Muscle A single Schwann cell wrap A single Schwann cellenvelopes Gamma(γ) 3-6 Heavy 15-30 ++ spindles around a single axon (in the several axons Pain, Delta(δ) 2-5 Heavy 12-30 +++ PNS) (Oligodendrocytes, Several Fibers are enveloped temperature Analogue of Schwann cells inCNS within singleclefts of Schwann Preganglionic Type B