Embryonic Development Pt. 2

There are two meanings of dermatome, what are they?

the area of somite that will become dermis AND after the embryonic stage, the dermis innervated by a single spinal nerve

function of peripheral sensory neurons

convey information from sensory receptors to the association plate

where are the somas of the peripheral sensory neurons found?

dorsal root ganglion outside of the spinal cord

what is somatic development responsible for?

segmental innervation of body structures

what occurs when the brain begins development?

closing of the superior neuropore day 28 of brain formation

list 2 different nerves found in the peripheral system

sensory and motor

sensory (afferent) fibers

convey neural impulses to the CNS from the sense organs (eyes) and from sensory receptors in various parts of the body (skin)

motor (efferent) fibers

convey neural impulses from the CNS to effector organs (muscles and glands)

spinal nerves arise from the spinal cord as ___

rootlets

rootlets converge to form ___ and ___

anterior (ventral/motor) root and posterior (doral/sensory) root

when roots converge, what is formed?

spinal nerves (spinal nerve roots) that contains both motor and sensory fibers

What is DAVE?

DA: dorsal root/afferent

VE: ventral root/efferent

After exiting the vertebral canal, spinal nerves immediately split into ___ and ___

anterior and posterior primary rami

T or F, terms "motor nerve" and "sensory nerve" are relative to the majority of fiber types

TRUE

Motor nerves also contain ___

sensory fibers, relaying proprioceptive information and pain

Nerves supplying sensory information also contain ___

motor fibers, serving smooth muscle

What does the posterior rami (PPR) supply?

nerve fibers to the synovial joints of the vertebral column

Where are the PPR found?

in deep muscles of the back and overlying skin in segmental pattern

Does the PPR merge or remain separate from one another?

remain separate, does not merge to form nerve plexuses

What does the anterior rami supply?

larger remaining areas: skin, muscles of the anterior and lateral regions of the trunk and extremities

How are the anterior rami distributed?

remains separate innervating in a segmental pattern

How is limb innervation formed?

rami merge with one or more adjacent rami forming somatic nerve plexuses

what do somatic nerve plexuses form?

multi segmental peripheral nerves

what does the anterior primary rami join to create?

nerve plexuses

what are the 5 different nerve plexuses

cervical C1-C4

brachial C5-T1

lumbar L1-L4

sacral L4-S4

coccygeal S5-C0

Plexuses and rami directly innervate skin and musculature as ___

peripheral nerves

Till when are the spinal cord segments adjacent to corresponding vertebrae?

until the third fetal month

T or F, as the fetus matures the spinal column grows slower than the cord

FALSE, faster

Where does the adult spinal cord end?

L1-L2 level, sometimes L3

conus medullaris

end of spinal cord

Where do nerves exit from the C/S?

roots exit immediately superior to corresponding vertebrae

Where do nerves exit from C8?

travels inferior to C7 and superior to T1

Where do nerves exit from the T/S?

roots exit immediately inferior to the corresponding vertebrae

Caudal to the thoracic levels, roots of the spinal nerves ___ ___ to reach the intervertebral foramina

travel inferiorly

cauda equina

collection of lumbosacral nerve roots that extend inferior to the end of the spinal cord

filum terminale

continuation of the dura, pia, and glia connecting the end of the spinal cord with the coccyx

segmental innervation

spinal nerves as they exit the spinal column ex: C1, C2., C3...

peripheral nerve innervation

comprised of nerve roots and have names ex: Femoral, obturator, sciatic

ASIA scale indicates ___

somatic innervation

When spinal cord is damaged, it is ___ or ___

complete or incomplete

everything below the level of the injury is ___ or ___

impaired (incomplete) or gone (complete)

spinal nerve (nerve root) injury

damage to specific spinal segment, everything innervated is impaired/gone

peripheral nerve injury

damage is in the peripheral nervous system, specific peripheral nerves are damaged

everything the peripheral nerve innervates is ___ below the level of the lesion

impaired/gone

what is the different between peripheral and nerve root injury?

all innervation is lost versus only specific nerves

with clinical application, how do we test nerve roots?

dermatomes, myotomes, deep tendon reflexes

with clinical application, how do we test peripheral nerves?

peripheral cutaneous nerve map , manual muscle testing of muscles innervated solely by the suspected peripheral nerve