Development of the Peripheral Nervous System

Question 1

gastrulation

Answer 1

is the formation of the three germ layers

cells are going to ingress thorugh the primitive streak and populate into the three different germ layers

Question 2

neurulation

Answer 2

taking ectoderm specifying it to become neural ectoderm
notochord induces neural plate formation in overlying ectoderm
forms neural folds –> neural tubes
pinches off ectoderm that will form epidermis from the underlying neural tube

Question 3

CNS

Answer 3

includes brain and spinal cord

arise from the neural tubre

Question 4

PNS

Answer 4

all components of the nervou system outside of the CNS 
Cranial nerves and ganglia 
spinal nerves and ganglia (DRG) 
autonomic nerves and ganglia 
enteric nervous system 

develops from neural tube
neural crest cells, neuroectoderm, ectodermal placodes

Question 5

modalities

Answer 5

sensory or motor
sensory comes in from the periphery (therefore afferent)
motor is efferent and goes to the periphery

Question 6

somatic sensory

Answer 6

sensations of the body - skin

Question 7

visceral sensory

Answer 7

sensations of internal organs/abdominal viscera

Question 8

somatic motor

Answer 8

motor innervation of skeletal muscle

Question 9

visceral motor

Answer 9

involuntary motor - smooth/cardiac muscle and glands
equivalent to ANS
parasympathetic division and sympathetic division

Question 10

gray matter can be divided into

Answer 10

posterior horn- sensory information
lateral - typically motor but related to autonomics
anterior horn - motor information

Question 11

white matter of spinal cord

Answer 11

not very many neuron cell bodies-  have myelinated axons, using this area as tracts to move up and down spinal cord 
can divide into: 
posterior funiculus 
lateral funiculus 
anterior funiculus 
ascending/descending tracts

Question 12

sulcus limitans

Answer 12

notochord division separating what will become dorsal and ventral regions

Question 13

neuroblasts from the neuroepithelium become

Answer 13

neurons

Question 14

glioblasts from the neuroepithelium become

Answer 14

astrocytes

Question 15

ependymal cells

Answer 15

special types of glial cells that are reponsible for becoming the chori plexus that becomes the CSF

Question 16

microglial cells are not derived from

Answer 16

neuroepithelium, come from mesenchymal cells - act as macrophage debris eaters

Question 17

neural tube divisions from inner to outer

Answer 17

ventricular zone (stem cells) 
Mantle/intermediate zone (migrating cells undergoing differentation - extend axons away from lumen toward outer surface) 
marginal zone (contains axons that will eventually be myelinated)

Question 18

mantle reorganizes into

Answer 18

alar (dorsal) columns
basal (ventral) columns
connected by roof plate and floor plate

Question 19

alar and basal columns run

Answer 19

all the way up and down vertebral column

Question 20

roof plate and floor plate provide

Answer 20

signals that induce differentiation of alar and basal column cells

Question 21

floor plate signal

Answer 21

sonic hedge hog - specifies motor neuron identity
ventral = motor
cool

Question 22

sonic hedge hog induces

Answer 22

motor neuron identity

Question 23

sonic hedgehog downstream products

Answer 23

NKX2.2 and NKX6.1

Question 24

roof plate signal

Answer 24

BMP (TGF-Beta family signaling molecule)
counteracts SHH gradient
responsible for induction of dorsal association neurons

Question 25

BMP4 downstream products

Answer 25

PAX3 and PAX7

Question 26

intermediolateral cell columns

Answer 26

T1-L3(thoracolumbar and sympathetic) S2-S4 (sacral and parasympathetic)
dorsalmost cells of the basal plate (and therefore are motor)
form the lateral horns (ANS precursors)

Question 27

cranial PNS derived from

Answer 27

NCC and ectodermal placodes - sensory ganglia of cranial nerves

Question 28

trunk PNS development

Answer 28

sensory neurons in DRG
Schwann cells (myelinate nerves)
sympathetic ganglia (pockets of neuronal cell bodies that contribute to
enteric nervous system

Question 29

axons exiting ventral horn pass through the

Answer 29

cranial sclerotome - form the ventral root - joined by lateral root (follows ventral root path)

Question 30

components of spinal nerves

Answer 30

posterior sensory information
ventral/anterior motor information
lateral autonomic information
spinal nerves are mixed sensory/motor modalities

Question 31

types of nerves

Answer 31

General somatic efferent (somatic motor)
general visceral efferent (ANS)
special visceral efferent (brachial muscles)
general somatic afferent (sensory in skin)
general visceral afferent (sensory of viscera)
special somatic afferent (hearing,balance,sight)
special visceral afferent (taste and smell)

Question 32

autonomics contain ___ neurons

Answer 32

2 neuron chain system

synapse in the ganglionic neuron

Question 33

sympathetic pathway

Answer 33

postgangiolic fibers release norepinephrine

preganglionic utilizes acetylcholine

Question 34

parasympathetic pathway

Answer 34

pre and postsynaptic (postganglionic) fibers release acetylcholine

Question 35

Myelinates CNS

Answer 35

oligodendrocytes
glial cells derived from neuroepithelium
begins in lower brain stem, older tracts first

Question 36

Myelinates PNS

Answer 36

schwann cells
NCC derived
motor roots myelinated before sensory roots