gray matter
nerve cell bodies lie within this
looks like an H
CELLULAR
divided into horns
white matter
interconnecting fiber tract systems
FIBER nature
funculi
anterior (ascending/descending motor tracks, pain and temperature tracks that ascend)
lateral (same as anterior)
posterior (sensory info from all areas of the body below the head taken up to areas of the brain)
afferent
sensory
toward CNS
efferent
motor
from the CNS
how many pairs of spinal nerves
31
how many thoracic nerves
12
how many cervical pairs
8
how many lumbar nerves
5
how many sacral
5
how many coccygeal nerves
1
NOTE: a ganglion exists on the dorsal root, which contains what?
the cells bodies of all the afferent sensory fibers, except for vagal afferents, below the level of the head
where does the first spinal nerve exit?
between the skull and CV1
how are spinal nerves numbered and where do they exit?
exit intervertebral foramina EXCEPT for in the cervical region
mixed nerve
motor and sensory formed at the junction of a dorsal and ventral root
dorsal root ganglion
is a nodule on a dorsal root of the spine that contains cell bodies of nerve cells (neurons) that carry signals from sensory organs toward the appropriate integration center.
nucleus-group of cell bodies found within the central nervous system
ganglion- nerve cell bodies located outside the CNS
dermatone
the unilateral area of skin innervated by the sensory fibers of a single spinal nerve
central nervous system
brain and spinal cord
PNS
12 cranial nerves and 31 pairs of spinal nerves
lateral horn
“column”
discontinuous
found from C8 to L2 and picks up again at L2-3,4
gives rise to autonomic (parasympathetic and sympathetic) nerve fibers (not under our control)
anterior horn
ventral
filled with cells that are motor cells that go to all muscles of your body
selectively stimulate one of these, a muscle would twitch
posterior horn
cell bodies that give rise to fibers that communicate with other areas
rootlets
coalesce to form root
which eventually form a single spinal nerve
spinal nerve
where dorsal and ventral roots come together ***
short entity (1 cm in length)
bifurcates and forms dorsal ramus and ventral ramus (larger)
are spinal cord segments and spinal column segments different? Do they correspond?
yes
and
no b.c the spinal cord does not span the entire length of the spinal column ***
spinal column segments–> vertebra
so if a T12 vertebra was crushed it would be effecting the lumbar spinal cord segments
spinal cord segment gives rise to …
rootlets –> roots–> spinal nerve–> bifurcate and form dorsal and ventral ramus
which will coalesce to form single spinal nerve
pseudounipolar sensory neuron
has both peripheral process (conducting impulses from the receptor organ) toward the cell body
and a central process (continues from the cell body into the CNS)
these are part of the PNS
brings in sensation information
their cell body sits in the dorsal root ganglion
central fibers come in a synapse will cell in the posterior horn
is there any part of your body that will not feel sensation ?
NO
nerves that go to all parts of your body have both sensory and motor components (mixed nerves)
so dorsal and ventral ramus are also mixed nerves!***
3 things that dorsal rami innervate
skin of the back
deep back muscles
zygopathoseal facet joints of back (joints of the spine)
ventral primary ramus
forms all the somatic nerve plexuses of the body
innervate ventral torso
somatic plexus
cervical
brachial
lumbosacral
fibers within spinal nerves
General somatic afferent
General visceral afferent
General somatic efferent
general visceral efferent
peripheral visceral structures?
you have visceral structures all over (so even a sweat gland is visceral structure out in the periphery, so not just in the gut)
errector pili organ
vessel
sweat gland
exteroreceptor
bringing things in to the CNS
interoreceptors
proprioceptive -understand and feel limbs in a certain position without looking at it
all of the visceral afferents or somatic afferents all have their cell bodies where? GSA’s and GVA’s
in the dorsal root ganglion
so if asked where you find cell bodies that are responsible for innervating the cutaneous areas of the skin, they are found in the dorsal root ganglion
the only spinal nerve that has reduced or absent dorsal root ganglion is…
spinal nerve C1
-has to do with development
anterior horn
where all the motor neurons (cell bodies) sit for all the skeletal muscles in the entire body below the head
general somatic afferent
transmit sensations from the body to the CNS
(transmit info from skeletal muscles, tendons, and joint capsules and from the outside of the boyd concerning pain, touch, and temp)
general somatic efferent
transmit impulses to skeletal muscles
general visceral afferent
transmit pain or subconscious visceral reflex sensations (distention, blood gas) from hollow organs and blood vessels to the CNS
general visceral efferent
transmit impulses to smooth muscle and glandular tissue
innvervate smooth muscles, cardiac muscle, and glands
autonomic
plexus formation comes from
following targets out periphery
two things about brachial plexuses
the fibers of a single spinal nerve entering the plexus are distributed to multiple branches of the plexus (one spinal nerve contributing fibers to many different peripheral nerves)
the peripheral nerves derived from the plexus contain fibers from multiple spinal nerves (one peripheral nerve distributing sensory fibers to many different spinal nerves)
posterior (primary) rami of spinal nerves
supply nerve fibers to the synovial joints of the vertebral column, deep muscles of the back and the overlying skin in a segmental pattern
as a general rule the posterior rami remain separate from each other (do not merge to form major somatic nerve plexuses)
dermatomal map
distribution of a single spinal nerve
-gives you spinal origin
no C5 in the trunk
difference between dermatone and peripheral nerve
area of skin innervated by a single spinal nerve
peripheral nerves may have several spinal nerves in them
- peripheral nerve delivers innervations to dermatones
- gives nervous origin that has many spinal levels within it
1 place that is a 1 to 1 correlation (of innervation of the skin by a single spinal nerve)
independent intercostal nerves