in this lecture we're going to talk about the spinal nerves so this a functional unit of the
spinal cord is a spinal segment and a spinal segment is that piece of the spinal cord to
and from which all of the rootlets of one single spinal nerve are attached so if you draw a line
here it's all of these so it's this here's the spinal nerve now here's labeled here obviously
in the spinal nerve you have a dorsal root and a ventral root and it's all of that real estate
within the spinal cord that is contributing motor fibers and receiving sensory fibers okay so that
is one spinal unit or one spinal segment which is the functional unit of the spinal cord and
of course the modalities are important so when we think of a spinal segment we think of one
spinal nerve and then of course all of its dorsal and ventral rootlets roots and then
the spinal nerve so you know that the dorsal part of the spinal of the spinal cord gray is
sensory and that the ventral is motor and so it goes without saying then or maybe with that
the dorsal rootlets and root are sensory the ventral rootlets and root are motor but they
come together here at the spinal nerve so the spinal nerve is mixed okay so sensory motor and
then mixed one more thing about the spinal nerves they split almost immediately after
becoming nerves so they extend just a little bit and then we have what is called a dorsal
primary ramus and it's dorsal because it's going towards your back and ramus means arm
so this is the part of the nerve that goes around and innervates your back so that you
can move your back muscles and so that you can feel the sun shining on it in the summertime
the ventral primary ramus is going to curve around the front and innervate your sides and
the anterior or ventral part of your body okay these are mixed right because they are branches
of that mixed spinal nerve so sensory motor mixed mixed and mixed the different components of the
spinal nerve reflect the different components of the spinal cord gray matter so remember that
somatic is voluntary visceral is autonomic so we have two zones in our dorsal horn we
have our somatic and our visceral and we have two components in our ventral horn somatic and
visceral so all four groups of these neurons are going to have are going to be represented in any
given spinal nerve so two motor components to sensory components come together for
four different modalities with in every spinal nerve okay so just to review somatic a ferrant
visceral a ferret visceral efferent and somatic efferent these neurons projecting out and the
neurons from the periphery projecting in representing the a ferret and in the next
segment we'll talk more about the nerves and how they distribute throughout the rest of the body