1. CNS – The Spinal Cord, Spinal Nerves & Spinal Reflexes

2. Spinal Cord & Spinal Nerves
Truly the pathway between body and mind
Conducts impulses to and from the brain
Carries out spinal reflexes
Spinal nerves
31 pairs
All are mixed nerves

3. Mixed Nerves? Dorsal roots Ventral roots
Ganglion containing axons of sensory neurons (afferent)
Ventral roots
All motor fibers (axons) leave the cord by the ventral roots (efferent)

4. General Organization
Highly organized, very efficient

5. Spinal Reflexes
Rapid, automatic nerve responses triggered by specific stimuli
Controlled by spinal cord alone; not the brain

6. Gross Anatomy of the Spinal Cord

7. The Adult Spinal Cord About 18 inches (45 cm) long
1/2 inch (14 mm) wide
Ends between vertebrae L1 and L2

8. Bilateral Symmetry Grooves divide the spinal cord into left and right
Posterior median sulcus:
Shallow
Anterior median fissure:
deeper groove on anterior side

9. Enlargements of the Spinal Cord
Caused by:
amount of gray matter in segment
involvement with sensory and motor nerves of limbs
Cervical enlargement:
nerves of shoulders and upper limbs
Lumbar enlargement:
nerves of pelvis and lower limbs

10. The Distal End Conus medullaris: Filum terminale:
thin, conical spinal cord below lumbar enlargement
Filum terminale:
thin thread of fibrous tissue at end of conus medullaris
attaches to coccygeal ligament

12. Meninges of the Spinal Cord

13. The Meninges
Specialized membranes isolate spinal cord from surroundings
Spinal meninges:
protect spinal cord
carry blood supply
continuous with cranial meninges
Meningitis:
viral or bacterial infection of meninges

14. The 3 Meningeal Layers Dura mater: Arachnoid mater: Pia mater:
outer layer of spinal cord
Arachnoid mater:
middle meningeal layer
Pia mater:
inner meningeal layer

15. Spinal Dura Mater Are tough and fibrous Cranially: Caudally:
fuses with periosteum of occipital bone
is continuous with cranial dura mater
Caudally:
tapers to dense cord of collagen fibers
joins filum terminale in coccygeal ligament

16. The Epidural Space
Between spinal dura mater and walls of vertebral canal
Contains loose connective and adipose tissue
Anesthetic injection site

17. Arachnoid Mater Middle meningeal layer Arachnoid membrane:
simple squamous epithelia
covers arachnoid mater

18. Inter-Layer Spaces
filled with cerebrospinal fluid (CSF)

19. Cerebrospinal Fluid (CSF)
Is found in subarachnoid space
Carries dissolved gases, nutrients, and wastes
Spinal tap:
withdraws CSF

20. Pia Mater Is the innermost meningeal layer
Is a mesh of collagen and elastic fibers
Is bound to underlying neural tissue

22. Spinal Cord Meninges

23. Sectional Anatomy of the Spinal Cord

24. Consists of…. White matter Gray matter Gray horns Posterior gray horns
contain somatic and visceral sensory nuclei
Anterior gray horns
contain somatic motor nuclei
Lateral gray horns
are in thoracic and lumbar segments
contain visceral motor nuclei

25. Spinal cord is so highly organized:
it is possible to predict results of injuries to specific areas

26. Spinal Nerves The roots unite into the spinal nerve
Spinal nerves exit through intervertebral foramen
Split into branches, or rami.

27. Dermatomes
Specific bilateral region of the skin surface monitored by a single pair of spinal nerves

28. Nerve Plexuses Plexus = “braid”
Nerves supplying the limbs form plexuses when they leave the spinal cord
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus