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Learn the intricate details of the central nervous system focusing on the spinal cord's structure, organization, and protective mechanisms. Explore how spinal nerves function and the significance of directional terms unique to the CNS.
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PART 1 The CentralNervous System
The Central Nervous System • Central nervous system • The brain and spinal cord • Directional terms unique to the CNS • Rostral – toward the nose • Caudal – toward the tail
The Spinal Cord • Functions of the spinal cord • Spinal nerves attach to it • Provides two-way conduction pathway • Major center for reflexes • Location of the spinal cord • Runs through the vertebral canal • Extends from the foramen magnum to the level of the vertebra L1 or L2
The Spinal Cord • Conus medullaris • The inferior end of the spinal cord • Filum terminale • Long filament of connective tissue • Attaches to the coccyx inferiorly • Cervical and lumbar enlargements • Where nerves for upper and lower limbs arise • Cauda equina • Collection of spinal nerve roots
The Spinal Cord Figure 13.2a
The Spinal Cord • Spinal cord segments • Indicate the region of the spinal cord from which spinal nerves emerge • Designated by the spinal nerve that issues from it • T1 is the region where the first thoracic nerve emerges
Spinal Cord Segments Figure 13.3
The Spinal Cord • Two deep grooves run the length of the cord • Posterior median sulcus • Anterior median fissure
White Matter of the Spinal Cord • White matter • Outer region of the spinal cord • Composed of myelinated and unmyelinated axons • Allow communication between spinal cord and brain • Fibers classified by type • Ascending fibers • Descending fibers • Commisural fibers
Gray Matter of the Spinal Cord and Spinal Roots • Shaped like the letter “H” • Gray commissure – contains the central canal • Dorsal horns • Consist of interneurons • Ventral and lateral horns • Contain cell bodies of motor neurons
Anatomy of the Spinal Cord Figure 13.4a
Anatomy of the Spinal Cord Figure 13.4b
Organization of the Gray Matter of the Spinal Cord • Gray matter • Divided according to somatic and visceral regions • SS – somatic sensory • VS – visceral sensory • VM – visceral motor • SM – somatic motor
Gray Matter of the Spinal Cord and Spinal Roots Figure 13.5
Protection of the Spinal Cord • Protected by vertebrae, meninges, and CSF • Meninges • Dura mater – a single layer surrounding spinal cord • Arachnoid mater – lies deep to the dura mater • Pia mater – innermost layer • Delicate layer of connective tissue • Extends to the coccyx • Denticulate ligaments – lateral extensions of pia mater
Cerebrospinal Fluid • Fills the hollow cavities of the brain and spinal cord • Provides a liquid cushion for the spinal cord and brain • Other functions • Nourishes brain and spinal cord • Removes wastes • Carries chemical signals between parts of the CNS
Diagram of Lumbar Puncture Figure 13.6