Download Adult spinal cord

Learning Objectives
• Discuss the structure and functions of the spinal
cord.
• Describe the three meningeal layers that surround
the CNS.
• Describe the major components of a spinal nerve
and relate their distribution to their regions of
innervation.
• Discuss the significance of neuronal pools.
• Describe the steps in a neural reflex.
• Explain how reflexes interact to produce
complicated behaviors.
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Divisions of the Nervous System
• CNS
• Brain and spinal cord
• In the white matter, axons arranged in tracts
and columns
• PNS
• Remainder of nervous tissue
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Figure 13.1 An Introduction to the Anatomical
Organization of the Nervous System
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Figure 13.1
Adult spinal cord
• Localized enlargements provide innervation to
limbs
• 31 segments
• each segment has a pair of dorsal roots and a
pair of ventral roots
• Filum terminale- Fibrous extension of the spinal cord,
from the conus medullaris to the coccygeal ligament.
• Conus medullaris- Conical tip of the spinal cord that
given rise to the filum terminale.
• Spinal nerves extend off cord
• Spinal nerves are classified as mixed nerves (contain
both afferent (sensory) and efferent (motor) fibers).
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Figure 13.3 Gross Anatomy of the Adult Spinal
Cord
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Figure 13.3
Spinal meninges
• Provide physical stability and shock absorption
• Three layers
• Dura mater- Outermost component of the cranial and
spinal meninges.
• Arachnoid- Middle meninx that encloses cerebrospinal
fluid and protects the CNS.
• Pia mater- Tough, outer meningeal layer that
surrounds the CNS.
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Dura mater
• Covers spinal cord
• Tapers to coccygeal ligament
• Epidural space separates dura mater from walls
of vertebral canal
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Figure 13.4 The Spinal Cord and Spinal
Meninges
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Figure 13.4a
Figure 13.4 The Spinal Cord and Spinal
Meninges
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Figure 13.4b
Arachnoid
• Interior to dura mater are the subdural space, the
arachnoid and the subarachnoid space
• Subarachnoid space contains CSF
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Pia mater
• Meshwork of elastin and collagen fibers
• Innermost meningeal layer
• Denticulate ligaments extend from pia mater to
dura mater
• Denticulate ligaments- Supporting fibers that extend laterally from
the surface of the spinal cord , tying the pia matter to the dura matter
and providing lateral support for the spinal cord.
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Figure 13.6 The Cervical Spinal Cord
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Figure 13.6
Sectional anatomy of the spinal cord
• White matter- Regions in the CNS that are
dominated by myelinated axons.
• Gray matter- Areas in the CNS that are dominated
by neuron cell bodies, neuroglia and unmyelinated
axons.
• Projections of gray matter toward outer
surface of cord are called horns.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.7 The Sectional Organization of the
Spinal Cord
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Figure 13.7a
Figure 13.7 The Sectional Organization of the
Spinal Cord
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Figure 13.7b
Horns of spinal cord
• Posterior gray horn contains somatic and visceral
sensory nuclei
• Somatic Nervous System (SNS)- The efferent division of the nervous
system that innervates skeletal muscle.
• Visceral- Pertaining to viscera or their outer coverings.
• Viscera- Organs in the ventral body cavity.
• Anterior gray horns deal with somatic motor
control
• Lateral gray horns contain visceral motor
neurons
• Gray commissures contain axons that cross from
one side to the other
• Commissure- A crossing over from one side to another.
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White matter
• Divided into six columns (funiculi) containing
tracts
• Ascending tracts relay information from the
spinal cord to the brain
• Descending tracts carry information from the
brain to the spinal cord
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings