Development of the peripheral nervous system Flashcards
Central Nervous System (CNS)
– Brain
– Spinal Cord
Peripheral Nervous System (PNS)
– Cranial nerves – Spinal nerves – Ganglia – Enteric plexus – Sensory receptors
gray matter
- location of cell bodies and neurons
- unmyelinated
dorsal (posterior) horn
sensory
lateral horn
autonomics
anterior (ventral horn)
motor
white matter
- location of axons
- myelinated
dorsal (posterior) funiculus
sensory
lateral funiculus
sensory and motor
anterior (ventral) funiculus
- primarly motor
what does the sulcus limitans separate?
alar plate from the basal plate
alar plate
sensory neurons that stay in CNS
basal plate
- motor neurons
- preganglionic neurons for ANS and neurons to musle
central canal
connected to ventricular system in brain
ventricular zone
-next to central canal
cells of ventricular zone
germinal or ventricular cells (stem cells)
- ependymoblast
- ependyma cell
- choroid plexus cells (makes CSF)
intermediate zone
-gray matter
intermediate zone cells
- astrocyte
- neuron
marginal zone
-white matter
marginal zone cells
- axon
- oligodendrocyte
what layer do mesenchymal and microglial cells come from?
mesoderm
position of spinal cord in newborns
L2 or L3
position of spinal cord in adults
L1 or L2
neural crest cells
give rise to
spinal ganglion cells and
sensory neurons in the
periphery
how is spinal cord formed
Dorsal (sensory) and ventral
(motor) region dependent on
concentration gradients
what does high BMP activate?
activate PAX3
and 7 = sensory neuron
differentiation = alar plate
what does high SHH activate?
NKX2.2 and NKX6.1 = ventral
neuron formation = basal plate
how are ventral motor neurons formed?
Just dorsal there are slightly lower
SSH and higher levels of BMP
activate NKX6.1 and PAX6
if there are high amount of BMP how will spinal cord be patterned?
dorsally
if there are high amount of SHH how will spinal cord be patterned?
ventrally
what forms the PNS
neural crest and ectodermal placode (from ectoderm)
what are cells that develop from neural tube?
- motor neurons
- pre ganglionic autonomic neurons (in lateral horn)
what are cells that develop from neural crest?
– Neurons of dorsal root ganglia – Sensory ganglia of cranial nerves – Schwann cells – Sympathetic ganglia – Parasympathetic ganglia
Dorsal root (sensory)
- spinal ganglion (dorsal root ganglion)
- neural crest
ventral root (motor)
-neuroectoderm
spinal nerve
mixed
dorsal ramus
- mixed
- motor to dorsal muscles (true muscles of back= epiaxial)
- sensory to dorsal integument
ventral ramus (mixed)
– Sensory to integument of
same regions
-motor to limbs, lateral and ventral body wall (hypomere/hypaxial)
ramus communicantes
-motor and sensory to viscera
(General somatic efferent):
somatic muscle
-neuroectoderm
GVE (General visceral efferent)
-autonomics to smooth and
cardiac muscle and glands
-neuroectoderm
SVE (Branchial or Special visceral efferent):
muscles derived
from the pharyngeal arches
-neuroectoderm
GSA (General somatic afferent)
-sensory in the skin, joint
capsule, tendon, muscle
-ectoderm or from mesoderm adjacent to ectoderm
-neural crest cells
GVA (General visceral afferent)
:sensory of visceral structures
– Endoderm or mesoderm adjacent to endoderm
-neural crest
SSA (Special somatic afferent):
hearing, balance and sight
SVA (Special visceral afferent):
-taste and smell
efferent somatic
Motor fibers
ending on
skeletal muscle
-neuroectoderm
efferent visceral
Motor fibers ending about autonomic ganglion cells which, in turn control smooth muscle, cardiac muscle and glands -neuroectoderm
Afferent
sensory
Sensory fibers originating chiefly from integument -neural crest cells
afferent (sensory)
Visceral:
Sensory fibers
originating
from viscera
-neural crest cells
Autonomic Nervous System (ANS)
• Innervation of smooth muscle, cardiac muscle and
glands.
what are two motor paths have ANS
– Sympathetic
– Parasympathetic
formation of ganglia and post-ganglion
cells. (ANS)
neural crest
formation of the pre-ganglion cells(ANS)
neuroectoderm
Sympathetic
Located in the spinal cord in the thoraco-lumbar
region (T1-L2)
preganglionic (sympathetic)
from spinal cord to sympathetic ganglia
- neuroectoderm
- short myelinated
postganglionic (sympathetic)
from ganglia to viscera
- neural crest
- long, not myelinated
Parasympathetic
Cranial-sacral region – Cranial: primarily cranial nerves
– Sacral: 2nd to 4th sacral spinal nerves (GVE)
Preganglionic (parasympathetic)
- from spinal cord to sympathetic ganglia
- neuroectoderm
- long and myelinated
postganglionic (parasympathetic)
- from ganglia to viscera
- neural crest cells
- short and unmyelinated
how many cranial ganglia are there?
4
what myelinates the CNS
- oligodendrocytes
- from neuroectoderm
- starts in lower brain stem first
- 6 months through puberty
what myelinates the PNS
- schwann cells
- neural crest ells
- motor roots myelinated before sensory roots
- 4th month
