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Jennifer LaVail, Ph.D.
(http://anatomy.ucsf.edu/Pages/
lavaillab/index.html)
Comparative Anatomy Terminology
Terms used for brain and
entire body are consistent in
rat.
However, the human brain
has a flexure, so above
midbrain the terms change.
The horizontal plane of the cerebral cortex is a longituinal plane in the spinal cord.
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BIG PICTURE
The Spinal Cord is composed of repeating segments.
8
12
5
5
Plan of the Spinal Cord
Each segment has the same elements.
Somatosensory afferents (fibers that come into the CNS)
Motoneuron axons or efferents (fibers that exit the CNS).
Interneurons (cells whose axons do not leave the CNS.
Repeating Plan of the Spinal Cord
Somatosensory afferents have their cell bodies in the dorsal
root ganglion outside of the CNS.
The afferents enter the spinal cord and synapse on the
same side of the cord.
The motor neurons that innervate muscles (smooth or
striated) are located on the same side of the cord as are
the muscles.
The interneurons have axons that synapse with other
interneurons or with motor neuron cells.
Functional Segment
Protective Layers for Spinal Cord
Vertebra
Segmental Arrangement of the Spinal Column
Segmental Organization of the Spinal Cord
Segmental Differences in Internal Structures
ARM
LEGS
Segmental Differences
B CNS
develops from a tube
Origins of Brain Divisions
Brain stem
Ventral brain
The Brainstem