Unformatted text preview: In summary:
1. Cell bodies of sensory cells lie in the dorsal root ganglia outside the spinal cord (but inside the spinal
2. Cell bodies of neurons that send messages to muscles (motoneurons) lie in the ventral horn.
3. Cell bodies of preganglionic1 autonomic efferents lie in lateral horn (not shown).
4.Spinal cord gray matter contains cell bodies of intemeurons. Intemeurons are small neurons with very
short axons and make connections locally. They are involved in information processing at the local
5.Spinal cord contains cell bodies of neurons that send axons out into the white matter. These axons
transmit information to the brain stem.
6.The 31 spinal nerves give rise to the peripheral nerves. These nerve bundles are composed of various
efferent (or motor) and sensory (afferents) nerves.
7.The size of each spinal segment, the size of its gray matter and the thickness of the segment vary from
segment to segment. Segments that send and receive information from the limbs are larger. The spinal cord is not just a relay station; it does a lot of complex processing of information. The
complete circuitry for locomotion and various reﬂexes lie in the spinal cord. An animal without the cortex
can walk, chew, lick and has all the reﬂexes. IDeﬁnition.‘ Ganglion is a collection of nerve cells Important Ascending and descending tracts means tracts which take information up to the brain, and down from
the brain, respectively. Ascending and Descending do not refer to any anatomical location - it refers
to just the functions of the tracts. A tract is named according to where it starts and where it ends. A tract is made up similar neurons.
Cell bodies (somata) of these neurons lie in one location, and their terminals synapse in another
location. For example: corticospinal tract (CST) means that the cell bodies of neurons comprising
CST lie in the cortex and their axons synapse in the spinal cord. Spinothalamic tract (ST hT) means
that the cell bodies of the neurons comprising ST hT lie in the spinal cord, and their axons synapse in
the thalamus. 0n the other hand dorsal roots refer to the axons entering the spinal cord from the dorsal side (back).
They happen to carry sensory information. Ventral roots are the axons that are located on the ventral side (front) of the spinal cord. They happen
to carry information from the spinal cord to the muscles. In this case, the function and location are
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- Fall '09