SPINAL CORD ANATOMY PHYSIOLOGY HONORS ANATOMY PHYSIOLOGY Spinal

SPINAL CORD ANATOMY & PHYSIOLOGY HONORS ANATOMY & PHYSIOLOGY

Spinal Cord w/spinal nerves contain neural circuits that mediate some of your most rapid reactions to environmental changes

Protective Structures 2 types of CT coverings surround & protect delicate nervous tissue 1. bony vertebrae 2. tough CT meninges, w/cushion of CSF

Meninges 3 CT coverings that encircle spinal cord & brain: Spinal meninges covers spinal cord Cranial meninges covers brain

Meninges Layers: Dura Mater “tough mother” most superficial layer made of dense, irregular CT continuous with cranial meninges forms sac from foramen magnum S 2 layer of adipose tissue between dura mater & wall of vertebral cavity (epidural space)

Middle Meninges: Arachnoid Mater “spider-like” deep to dura mater, superficial to pia mater contiguous with cranial arachnoid between dura & arachnoid = subdural space

Innermost Meninges: Pia mater “delicate” thin, transparent CT adheres to spinal cord & brain between arachnoid & pia = subarachnoid space

Spinal Tap aka lumbar puncture long needle inserted into subarachnoid space adults: between L 3 –L 4 or L 4 – L 5 (inferior to lowest portion of spinal cord) purpose: withdraw CSF for � diagnostic purposes � insert antibiotics/contrast media for myelography/ anesthetics/ chemotherapy

Spinal Cord cylindrical with flattening of its AP diameter adults: extends from medulla oblongata L 2 vertebra newborns: extends to L 3 or L 4 elongation of spinal cord stops ~age 3 -4 but growth of vertebral column continues

Spinal Cord: External View 2 obvious enlargements noted: � cervical enlargement � lumbar enlargement C 4 – T 1 serve upper limbs T 9 - T 12 serve lower limbs

Spinal Cord: External View conus medullaris: tapered conical structure of spinal cord below lumbar enlargement ending @ L 1 – L 2 filum terminale: extension of pia mater extends inferiorly & anchors cord to coccyx cauda equinae: “horse tail” nerves that arise from lumbar, sacral, & coccygeal portions of spine

Conus Medullaris

Filum Terminale

Cauda Equina

Spinal Nerves 31 pairs spinal nerves emerge thru intervertebral foramen 8 pair cervical nerves: C 1 – C 8 12 pair thoracic nerves: T 1 - T 12 5 pair lumbar nerves: L 1 – L 5 5 pair sacral nerves: S 1 – S 5 1 pair coccygeal nerves: Co 1

Spinal Nerves 2 bundles of axons, called roots, connect each spinal nerve to segment of spinal cord

Spinal Cord Roots 1. posterior (dorsal) root � � 2. only sensory axons each has dorsal root ganglion containing cell bodies of sensory neurons anterior (ventral) root � only motor axons

Internal Anatomy of Spinal Cord 2 grooves penetrate white matter & divide it in right & left sides: 1. anterior median fissure 2. 1. deeper, wider of the 2 1. shallower, narrow furrow posterior median sulcus

Internal Anatomy of Spinal Cord gray matter shaped like “H” or a butterfly & is surrounded by white matter gray commissure forms the “H” crossbar � central canal small hole in its center extends entire length of spinal cord filled with CSF @ superior end is contiguous with 4 th ventricle of brain

Spinal Nerves & the nerves that branch off them are part of PNS emerge from vertebral column thru intervertebral foramina

Spinal Nerves typically has 2 connections to spinal cord 1. 2. dorsal root (sensory) ventral root (motor) classified as “mixed”

Distribution of Spinal Nerves

Spinal Nerve Plexuses a network of nerves (or veins, or lymphatic vessels)

Cervical Plexus supplies skin & muscles of the head, neck, & superior portion of shoulders, chest, & diaphragm C 1 – C 5

Brachial Plexus supplies the shoulders & upper limbs

Lumbar Plexus supplies anterolateral abd wall, external genitals, part of lower limb

Sacral Plexus supplies buttocks, perineum, & lower limbs

Dermatomes cutaneous area developed from one embryonic spinal cord segment & receiving most of its sensory innervation from one spinal nerve knowing which spinal cord segments supply each dermatome makes it possible to locate damaged regions of the spinal cord

Reflexes & Reflex Arches reflex: a fast, automatic, unplanned sequence of actions that occurs in response to a particular stimulus can be: 1. inborn � 2. pulling hand away from hot stove learned or acquired � foot on brake when see dog run in front of car

5 Parts of a Reflex Arc

Stretch Reflex

Pupillary Light Reflex pupils of both eyes decrease in diameter when either eye is exposed to light absence of a normal pupillary light refex indicates possibility of brain damage or injury

Spinal Cord Injuries most due to trauma � cervical, lower thoracic, upper lumbar most common regions involved paralysis � depends on location, extent of damage � monoplegia: 1 limb � paraplegia: both lower limbs � hemiplegia: upper limb, trunk, lower limb on 1 side of body � quadriplegia: all 4 limbs & trunk

Extent Muscle Paralysis C 1 – C 3: no function neck down, requires ventilator to breathe C 4 – C 5: diaphragm, allows breathing C 6 – C 7: some arm, chest, allows breathing, moving wheelchair T 1 – T 3: intact arm function T 4 – T 9: control of trunk above umbilicus T 10 – L 1: most thigh muscles, walk w/long leg braces L 1 – L 2: most leg muscles, walk w/short leg braces

Shingles acute infection of PNS caused by herpes zoster (chicken pox) virus stays in posterior root ganglion � becomes reactivated normally immune system will prevent it from spreading � reactivated virus can overcome weakened immune system leaves ganglion travels down sensory neurons supplying skin

Medical Terminology meningitis: inflammation of meminges due to infection, bacterial (worse) or viral, vaccine protests against some bacterial causes: headache, N/V, fever, stiff neck neuralgia: pain along a sensory nerve, trigeminal neuralgia neuritis: inflammation of 1 or several nerves paresthesis: abnormal sensation