Development of the Peripheral System Flashcards
when is the critical period of embryo development
3-8 weeks and this is usually where things go wrong
how are somites used clinically
can detect the age of the embryo with an ultrasound and depending on the number of the somites distinguish the age
Peripheral Nervous System
Cranial nerves spinal nerves ganglia Enteric plexus Sensory receptors
Somatic=voluntary and carry sensory and motor
Autonomic= involuntary to smooth muscle and cardiac muscle and have both Motor and Sensory
-majority parasympathetic and sympathetic (technically motor)
Dorsal horn is composed of
Sensory cell bodies
Lateral Horn is composed of
Autonomic cell bodies
Anterior horn is composed of
Motor cell bodies
Dorsal Funiculus is composed of
Sensory axons that are mylenated (white)
Anterior Funiculus is composed of
Primarily motor axons
Lateral funiculus is composed of
sensory and motor axons
Neural tube caudal to the 4th somite regions:
Alar plate
Basal Plate
Central canal
Alar plate
sensory neurons that stay inside the brain, usually second and third order neurons
come from neuroectoderm
Basal Plate
Motor structures like brachial plexus
Central canal
hollow portion of the spinal cord tube
what are the three zones and location
Ventricular zone: closest to central canal
Intermediate zone: middle layer and gives rise to grey matter
Marginal zone: outside layer and gives rise to the axons and white matter
Ventricular zone structures
stem cells that make Ependymoblast which give rise to choroid plexus cell that creates Cerebrospinal fluid
also make ependymal cells
Intermediate zone structures
gives rise to the neurons cell bodies as well as astrocytes and radial glial cells
grey matter
Marginal zone structures
white matter
axons and oligodenrocytes which make mylein to put on the axons
Mesenchymal cell orgin and what do they make in the CNS
come from mesoderm and produce microgilal cells
Spinal cord positioning on newborns and why
L2 or L3 due to the growing of the bones because in the third month of the utero the spinal cord goes to the end of the spinal column
Spinal cord positioning on adults
L1 or L2
What does neural crest give rise to in the PNS
Spinal ganglion cells and sensory neurons in the periphery
what does BMP do and what side is it released from
released from roof plate and epidermis on dorsal side
and gradient gets smaller as it goes done
High BMP activate PAX3 and PAX7 which give rise to alar plate (sensory neurons)
what does SHH do and what side is it released from
released from Notochord and Floor plate on ventral side
activates NKX2.2 and NKX6.1 which gives rise to the basal plate
Mixing of the BMP and SHH
occurs just dorsal of the basal plate where there are slightly lower SSH and higher levels of BMP activates NKX6.1 and PAK6 which makes up ventral Horn and ventral horn neurons
Cells that develop from the Neural tube
motor neurons because the bodies are in the CNS
and preganglionic autonomic neurons (because located in lateral horn)
Cells that develop from the neural crest
Neurons of the dorsal root ganglia, in the PNS
sensory of the Cranial Nerves
Schwann cells
sympathetic and parasympathetic ganglia
Efferent Neurons
Motor derived from neuroectoderm
Somatic: motor ending on skeletal muscle
Visceral: Motor fibers that end about the autonomic ganglion cells which in turn control smooth muscle and cardiac and glands
Afferent Neurons
Sensory derived from the neural crest
Somatic: sensory fibers that originate from the integument
Visceral : sensory fibers originating from the viscera
Autonomic Nervous System
Motor:
Sympathetic and Parasympathetic
Neural crest in Autonomic Nervous system:
formation of Autonomic ganglia and post synaptic cells
Neuroectoderm in Autonomic Nervous system:
formation of the pre-ganglion cells and pre-synaptic cells
originate in the lateral horn
Sympathetic Nervous system
Located in the spinal cord in the thoracolumbar region: T1-L2/3 in lateral horn
two link chain
Short mylenated Preganglionic (neuroectoderm) from spina cord to sympathetic ganglia
(neural crest)
long unmylenated postganglionic fiber to ganglia to viscera
(all neural crest)
important sympathetic gaglion
Superior, middle and inferior cervical ganglion: all go to head and heart
Celiac ganglion
aorticorenal ganglion
superior mesenteric ganglion
inferior mesenteric ganglion
Parasympathetic Cranial sacral region
CN 3, 7, 9, 10
sacral: 2nd, 3rd, and 4th sacral spinal nerves
Parasympathetic two chain system
long mylenated (neuroectoderm) Preganglionic from spinal cord to parasympathetic ganglia
short unmylenated postganglionic fiber from ganglia to viscera (neural crest for all)
Ganglia found in wall of viscera
important parasympathetic ganglia
cilary ganglion
pterygopalatine ganglion
submandibular ganglion
otic ganglion
all neural crest
Oligodendrocytes
myelination in the CNS and starts in lower brain stem: older tracts first
6th months till 22 years old
neuroectoderm
Schwann cells
PNS myelination
motor roots before sensory roots
4th month
neural crest
