Biology 211 Anatomy & Physiology I

1. Biology 211Anatomy & Physiology I The Spinal Cord

2. Human Central Nervous System Starts as a groove which becomes a hollow tube in the embryo; Remains hollow & fluid-filled throughout life; These fluid-filled spaces form the ventricles of the brain and the central canal of the spinal cord. Cranial end of this hollow tube enlarges & folds to form brain and its various parts Caudal end of this hollow tube does not enlarge or fold; Develops into spinal cord

3. Central Nervous System Brain Spinal cord Nerves which carry information into and out of the brain and spinal cord = Peripheral Nervous System =

5. Spinal cord surrounded by 3 layers of connective tissue: Pia Mater Arachnoid Mater Dura Mater

6. Subarachnoid Space Subdural Space Epidural Space (Vertebrae) Pia Mater Arachnoid Mater Dura Mater

7. The spinal cord is protected in three ways: 1) Vertebrae (bone) 2) Meninges Pia Mater Arachnoid Mater Dura Mater 3) Floats in cerebrospinal fluid in subarachnoid space

8. Cerebrospinal fluid produced within ventricles by choroid plexus. Exits from fourth ventricle through three openings (apertures or foramina) into the subarachnoid space. Median Aperture Two Lateral Apertures Surrounds brain & spinal cord. Reabsorbed into blood through arachnoid villi on surface of brain

9. Posterior Median Sulcus Central Canal Anterior Median Fissure

10. Recall: In brain and spinal cord Gray Matter: Nervous tissue of the CNS consisting of neuron cell bodies, their supporting glia, and unmyelinated axons & dendrites. White Matter: Nervous tissue of the CNS consisting of myelinated axons & dendrites and their supporting glia White Matter Gray Matter

11. Gray Matter of Spinal Cord Dorsal (Posterior) Horn: Cell bodies of neurons which receive afferent information from spinal nerves and send it toward the brain Lateral Horn: Cell bodies of neurons which receive efferent information from the brain and send it to smooth myocytes, cardiac myocytes, and glands (autonomic motor innervation) Ventral (Anterior) Horn: Cell bodies of neurons which receive efferent information from the brain and send it to skeletal myocytes (somatic motor innervation)

12. White Matter of Spinal Cord Myelinated axons carrying information between brain and gray matter of spinal cord (both directions). Dorsal (Posterior) Column: Lateral Column: Ventral (Anterior) Column: Within each column, axons with same functions organized into bundles called tracts

13. That white matter is formed by the axons of both motor neurons and sensory neurons which are grouped into “tracts”

15. Tracts of the spinal cord are described in your text. You should be able to describe, in moderate detail, at least one ascending tract and one descending tract: Where it begins Where it ends If it deccusates Where it is located in the spinal cord What type of information it carries What would happen if it were damaged

16. Spinal cord gives rise to spinal nerves. A pair of spinal nerves (one on each side) exits between each pair of vertebrae from the atlas (cervical 1) to the first vertebra of the coccyx

17. Each nerve connects with spinal cord through two roots: Dorsal (posterior) root Carries afferent information into dorsal horn of gray matter Ventral (anterior) root Carries efferent information away from ventral horn of gray matter

18. Spinal nerves are named according to which vertebrae they pass between: 8 cervical nerves 12 thoracic nerves 5 lumbar nerves 5 sacral nerves 1 coccygeal nerve Levels of the spinal cord are named according to which spinal nerve carries information in/out of it.

19. Spinal nerves are named according to which vertebrae they pass between: 8 cervical nerves 12 thoracic nerves 5 lumbar nerves 5 sacral nerves 1 coccygial nerve Levels of the spinal cord named according to which spinal nerve carries information in/out of it. Thus: Spinal cord level "cervical 5" is defined as the region where spinal nerve "cervical 5" connects

20. Months before you were born, your spinal cord reached all the way through your sacrum, but as you continued to develop it grew less quickly than the vertebrae which surround it. At birth, your conus medullaris was at lumbar vertebrae 3 or 4. It now lies between lumbar vertebrae 1 and 2. That means that dorsal Roots and ventral roots of the spinal nerves must extend inferiorly to reach the proper intervertebral foramina, forming the cauda equina which is in the subarachnoid space.

21. Next: Let's follow the spinal nerves distally as they form the peripheral nervous system.