Transcript SC&SN-07
• Quiz #3 available today at 3pm until Monday at 11pm Use the diagram to label: 1. Sensory (afferent) neuron 2. Motor (efferent) neuron 3. CNS 4. PNS 5. Interneuron Spinal cord and spinal nerves • spinal cord anatomy • spinal meninges • where to put that needle • spinal cord terminology • spinal nerves • ascending and descending tracts • where do spinal nerves go? • dermatomes • nerves plexuses • cervical plexus • brachial plexus • simple reflexes • anatomy of spinal cord injuries 31 PAIR of spinal nerves • 8 cervical • 12 thoracic • 5 lumbar • 5 sacral • 1 coccygeal Medullary cone Cauda equina infant adult Meninges of the spinal cord Dura mater (pink) Pia mater Subarachnoid space Arachnoid mater (blue) Dura mater is continuous with epineurium of nerve fibers Denticulate ligament Coccygeal ligament 1. From which space is a spinal tap taken from? 2. Into which space is spinal anesthetic injected? 3. Into which space is an epidural anesthetic injected? Dura mater and arachnoid Pia mater Subarachnoid space Spinal tap or spinal anesthesia Epidural anesthesia Anatomy of the spinal cord Posterior (dorsal) sulcus Posterior (dorsal) horn Central canal (CSF) Spinal nerve Anterior (ventral) horn Anterior (ventral) fissure Fissure >> sulcus Nerve roots Gray and White Matter • White matter = myelinated nerve fibers • Gray matter = nerve cell bodies, dendrites, neuroglia & unmyelinated axons Nerve Fiber = nerve process (axon or dendrite) Nerve = bundle of nerve fibers in PNS (mixed) Tract = bundle of nerve fibers in the CNS (mixed) Ganglion = cluster of neuronal cell bodies in PNS Nucleus = cluster of neuronal cell bodies in the CNS 1. Label anterior and posterior. 2. Label a nerve root and a spinal nerve. 3. What is in the central canal? 4. Label the posterior (dorsal) horn. 5. What is it composed of? Sensory or ascending tracts Motor or descending tracts The spinal cord is very organized – anatomically & functionally brain midbrain medulla • Ipsilateral • Contralateral • Decussation spinal cord Ascending tract (Sensory info) 3rd order neuron Thalamus Midbrain 2nd order neuron Medulla 1st order neuron Decussation in medulla Somatosensory cortex Fig. 14.4(TE Art) Thalamus Midbrain Midbrain Gracile fasciculus Below T6 (legs) Medulla Cuneate fasciculus Above T6 (arms) Fine touch, proprioception, pressure Spinothalamic tract pain, heat, and cold Ascending tract summary Descending tracts Motor info Corticospinal tract Motor cortex Upper motor neurons Midbrain Medulla Lateral corticospinal tract Ventral corticospinal tract Lower motor neurons To skeletal muscles Damage to motor neurons….. Paralysis • loss of muscle function • causes? • para, quad, hemi - plegia Upper motor neurons Spastic paralysis Amyotrophic Lateral Sclerosis • degeneration of upper and lower motor neurons • paralysis of voluntary muscles • Lou Gehrig 1903-1941 & Stephen Hawking 1942- Poliomyelitis • degeneration of lower motor neurons • occurs in ventral horn • caused by polio virus Lower motor neurons Flaccid paralysis Spinal nerves 31 PAIR of spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Vertebral level vs spinal level Spinal nerve anatomy Dorsal root ganglion Dorsal ramus Ventral ramus Thoracic cavity Intercostal nerve Spinal Nerves 1. dermatomes 2. plexuses 3. reflexes Each spinal nerve innervates 1 somite Somite = skin, muscles, bones Dermatome – area of skin supplied by the sensory nerve fibers of one spinal nerve – Characteristic pattern – No dermatome for C1 (motor only) – Use dermatomes to access spinal nerve damage Cervical plexus (C1 –C5) Nerve Plexuses: Ventral rami traveling together Brachial plexus (C5–T1) Thoracic nerves (12 pairs) No plexus in thoracic region Lumbar plexus (L1–L4) Sacral plexus (L4 –S4) Sciatic nerve sciatica Fig. 14.13(TE Art) C1 C2 C3 C4 C5 Cervical plexus • C1-C5 • ventral rami • neck & shoulder • phrenic nerve Phrenic nerve C3-C5 Phrenic nerve • C3-5 • motor to diaphragm • skeletal muscles Brachial plexus • C5-T1 • ventral rami • arm & shoulder • Brachial plexus passes deep to the clavicle • Damage to brachial plexus Brachial plexus damage Lower motor neuron lesion = flaccid paralysis A simple reflex arc Information relayed to brain - slower Sensory neuron Info processing in CNS Motor neuron ** Don’t need the brain to have a reflex ** The Stretch Reflex Too much stretch, too fast Contract muscles to protect them You are an EMT - Frank dove into shallow end - you evaluate him and find: - his neck hurts - he can breath well on his own - he can’t feel or move his legs - he can’t feel his pinky - he can feel his thumb Where is his injury?? Spinal cord injuries (SCI) • SCI’s are damage to the spinal cord (vs vertebral column) • damage occurs from severing, stretching or compression • result in loss of motor & sensory function below injury site • can be complete or incomplete • flaccid paralysis immediately after injury (due to spinal shock) • spastic paralysis after spinal shock subsides Back to Frank….. 1. Can he breath on his own? 2. Will he be able to move/feel his legs? His arms? 3. Upper or lower motor neuron lesion? 4. What kind of paralysis will Frank have? - during spinal shock = flaccid paralysis, no reflexes - after spinal shock = spastic paralysis, uncontrolled reflexes