Spinal Cord Notes

ANATOMY OF SPINAL CORD Extends from medulla oblongata Ends at second lumbar (L2) vertebra in adults 31 pairs of spinal nerves Conus medularis – end of cord

Two enlargements: Cervical enlargement - C4 – T1 – nerves to & from upper limbs Lumbar enlargement – T9-T12 – nerves to & from lower limbs

Cauda equina = “horse’s tail” After conus medullaris, spinal cord divides into nerves that leave at lower levels

CROSS SECTION ANATOMY Two grooves divide spinal cord: Anterior median fissure (deeper) Posterior median sulcus Gray matter (unmyelinated) forms an “H” in center Gray commissure where fibers cross from side to side

Central canal – center of gray commisure; continuous with fourth ventricle Gray matter is divided into horns: Anterior (ventral) gray horns - cell bodies of motor neurons to skeletal muscle

Posterior ( dorsal ) gray horns Lateral gray horns – cell bodies of motor neurons to cardiac, and smooth muscle & glands Part of autonomic nervous system

White matter (myelinated nerve fibers) is divided into columns Anterior (ventral), posterior (dorsal), lateral white columns

Each column is divided into nerve tracts Each tract carries one type of information (sensory or motor) Ascending (sensory) tracts - impulses toward brain Descending (motor) tracts – impulses from brain

Spinal cord has two functions: White matter tracts serve as information highways to and from brain Gray matter receives and integrates information, especially for spinal reflexes

Name of tract indicate position in cord, where it begins and ends, and direction of impulses

DEVELOPMENT OF NS Begins in third week of development Ectoderm forms a neural tube Neural tube defect due to low levels of a folic acid Spina bifida – failure of laminae of spine to unite, caused by low levels of folic acid

Portions of neural tube form fluid-filled vesicles Hypothalamus is one of last areas of brain to develop No new neurons form after birth, only grow and maturation Brain reaches maximum weight as a young adult