After completing this unit, you should be able to: Describe the embryonic development of the spinal cord; describe the gross and microscopic structure of the spinal cord; list the major spinal cord tracts, and classify each as a motor or sensory tract; distinguish between flaccid and spastic paralysis, and between paralysis and paresthesia;...
Trang 1PowerPoint ® Lecture Slides
prepared by Janice Meeking, Mount Royal College
C H A P T E R
Copyright © 2010 Pearson Education, Inc.
12
The Central Nervous
System:
Part D
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The Spinal Cord: Embryonic Development
neuroblasts
form white matter of cord
axons will grow to effectors
sensory neurons; axons grow into the dorsal aspect of the cord
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White
matter
Neural tube cells
Central cavity
Alar plate:
interneurons
Dorsal root ganglion: sensory
neurons from neural crest
Basal plate:
motor neurons
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Spinal Cord
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Spinal Cord: Protection
epidural space between the vertebrae and spinal dura mater
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Spinal Cord: Protection
that secure cord to dura mater
medullaris; anchors the spinal cord to the
coccyx
Trang 7Copyright © 2010 Pearson Education, Inc. Figure 12.30
Ligamentum flavum
spinous ligament
Supra-Lumbar puncture needle entering subarachnoid space
Filum terminale
vertebral disc
Inter-T 12
L 5
Cauda equina
in subarachnoid space
Dura mater
L 5
L 4
S 1
Arachnoid matter
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Cervical enlargement
Dura and arachnoid mater
Lumbar enlargement Conus
medullaris Cauda equina Filum terminale
Cervical spinal nerves
Lumbar spinal nerves
Sacral spinal nerves
Thoracic spinal nerves
(a) The spinal cord and its nerve roots, with the bony vertebral arches removed The dura mater and arachnoid mater are cut open and reflected laterally.
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Spinal Cord
emerge here
of the vertebral canal
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Cross-Sectional Anatomy
and left halves
matter; encloses central canal
Trang 11Copyright © 2010 Pearson Education, Inc. Figure 12.31a
(a) Cross section of spinal cord and vertebra
Epidural space
Spinal meninges
Arachnoid mater
Dura mater
Bone of vertebra
of vertebra
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(b) The spinal cord and its meningeal coverings
Dorsal funiculus
Dorsal median sulcus
Central canal
Ventral median fissure
Pia mater Arachnoid mater Spinal dura mater
Gray commissure Dorsal horn Gray
matter Lateral horn
Ventral horn
Ventral funiculus Lateral funiculus
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Gray Matter
somatic and visceral sensory input
axons exit the cord via ventral roots
regions) –sympathetic neurons
bodies of sensory neurons
Trang 14Copyright © 2010 Pearson Education, Inc. Figure 12.32
Somatic
sensory
neuron
Dorsal root (sensory)
Dorsal root ganglion
Ventral horn (motor neurons)
Dorsal horn (interneurons)
Somatic motor neurons
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White Matter
descending (motor) tracts
from one side to the other
(funiculi on each side—dorsal (posterior),
lateral, and ventral (anterior)
similar functions
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Pathway Generalizations
relationships)
each side of the spinal cord or brain)
Trang 17Copyright © 2010 Pearson Education, Inc. Figure 12.33
Fasciculus gracilis Dorsal
Lateral corticospinal tract
Lateral reticulospinal tract
Ventral corticospinal tract
Medial reticulospinal tract
Rubrospinal tract
Vestibulospinal tract Tectospinal tract
Ventral
spinocerebellar
tract
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Ascending Pathways
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Ascending Pathways
information to the sensory cortex via the thalamus
cerebellum
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Dorsal Column-Medial Lemniscal Pathways
for discriminative touch and vibrations
and fasciculus gracilis in the spinal cord and the medial lemniscus in the brain (medulla to thalamus)
Trang 23Copyright © 2010 Pearson Education, Inc. Figure 12.34a (2 of 2)
Joint stretch receptor (proprioceptor)
Cervical spinal cord
Touch receptor
Medial lemniscus (tract)
(axons of second-order neurons)
Dorsal spinocerebellar
tract (axons of
second-order neurons)
Nucleus gracilis Nucleus cuneatus
Lumbar spinal cord
(a) Spinocerebellar
pathway Dorsal column–mediallemniscal pathway
Trang 24Copyright © 2010 Pearson Education, Inc. Figure 12.34a (1 of 2)
Primary somatosensory cortex
Axons of third-order neurons
Thalamus
Cerebrum Midbrain
Cerebellum Pons
(a) Spinocerebellar
pathway Dorsal column–mediallemniscal pathway
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Anterolateral Pathways
impulses within the lateral spinothalamic tract
Trang 26Copyright © 2010 Pearson Education, Inc. Figure 12.34b (2 of 2)
Axons of first-order neurons
Temperature receptors
Lateral spinothalamic
tract (axons of
second-order neurons)
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Primary somatosensory cortex
Axons of third-order neurons
Thalamus
Cerebrum Midbrain
Cerebellum Pons
(b) Spinothalamic pathway
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Spinocerebellar Tracts
stretch to the cerebellum
Trang 29Copyright © 2010 Pearson Education, Inc. Figure 12.34a (2 of 2)
Joint stretch receptor (proprioceptor)
Cervical spinal cord
Touch receptor
Medial lemniscus (tract)
(axons of second-order neurons)
Dorsal spinocerebellar
tract (axons of
second-order neurons)
Nucleus gracilis Nucleus cuneatus
Lumbar spinal cord
(a) Spinocerebellar
pathway Dorsal column–mediallemniscal pathway
Trang 30Copyright © 2010 Pearson Education, Inc. Figure 12.34a (1 of 2)
Primary somatosensory cortex
Axons of third-order neurons
Thalamus
Cerebrum Midbrain
Cerebellum Pons
(a) Spinocerebellar
pathway Dorsal column–mediallemniscal pathway
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Descending Pathways and Tracts
spinal cord
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Descending Pathways and Tracts
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The Direct (Pyramidal) System
precentral gyri pass through the pyramidal (corticospinal)l tracts
horn motor neurons
(skilled) movements
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Primary motor cortex Internal capsule
Cerebral peduncle
Midbrain Cerebellum Cerebrum
Pons
(a)
Pyramidal cells (upper motor neurons)
Pyramidal (lateral and ventral corticospinal) pathways
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Medulla oblongata
Cervical spinal cord
Skeletal muscle
Pyramids Decussation
of pyramid
Lateral corticospinal tract
Ventral corticospinal tract
Lumbar spinal cord
Somatic motor neurons (lower motor neurons)
(a) Pyramidal (lateral and ventral corticospinal) pathways
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Indirect (Extrapyramidal) System
motor pathways except pyramidal pathways
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Indirect (Extrapyramidal) System
multisynaptic, and regulate:
posture
objects
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Indirect (Extrapyramidal) System
maintain balance
mediate head movements in response to visual stimuli
Trang 39Copyright © 2010 Pearson Education, Inc. Figure 12.35b (1 of 2)
Midbrain Cerebellum
Trang 40Copyright © 2010 Pearson Education, Inc. Figure 12.35b (2 of 2)
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Spinal Cord Trauma
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Spinal Cord Trauma
ventral root or ventral horn cells
voluntary or involuntary control of muscles
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Spinal Cord Trauma
neurons of the primary motor cortex
stimulated by reflex activity
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Spinal Cord Trauma
regions inferior to the cut
region
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Poliomyelitis
by the poliovirus
respiratory muscles or cardiac arrest
many years later, as neurons are lost
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Amyotrophic Lateral Sclerosis (ALS)
horn motor neurons and fibers of the
pyramidal tract
swallow, and breathe
the immune system, or both
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Developmental Aspects of the CNS
• CNS is established during the first month of
development
• Gender-specific areas appear in both brain and
spinal cord, depending on presence or absence of fetal testosterone
• Maternal exposure to radiation, drugs (e.g., alcohol and opiates), or infection can harm the developing CNS
• Smoking decreases oxygen in the blood, which can lead to neuron death and fetal brain damage
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Developmental Aspects of the CNS
the CNS to develop
weeks
superior-to-inferior and proximal-to-distal
directions along with myelination
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Developmental Aspects of the CNS
are not significant in healthy individuals until they reach their 80s
senility unrelated to the aging process