Development of the Peripheral Nervous System

Question 1

What comprises the CNS

Answer 1

Brain, spinal cord (anything within skulls and vertebral column

Question 2

What comprises the PNS (examples)

Answer 2

Anything not CNS — cranial nerves, spinal nerves, ganglia, enteric plexus, sensory receptors, etc.)

Question 3

Subclassifications of the PNS and what they control

Answer 3

Somatic – sensory motor TO the body, aware from nervous system, under VOLUNTARY control

Autonomic – Involuntary, back to body, handles: smooth muscle, cardiac muscle, glands, etc for anything that you don’t have to think about

KEY: both have a sensory AND a motor component

Question 4

Gray Matter, their subsets and what they control

Answer 4

Location of cell bodies of neurons

1) posterior horn – sensory
2) lateral horn – autonomics
3) anterior – motor

Question 5

White Matter, their subsets and what they control (also, why called white matter???)

Answer 5

Location of axons

BECAUSE IT’S MYELINATED!!!

1) Posterior Funiculus (connection of axons) - sensory
2) Lateral funicular - motor and sensory
3) anterior funicular – motor

Question 6

Where is the neural tube located?

Answer 6

Caudal to the 4th pair of somites

Question 7

What is the sulcus limitans?

Answer 7

the barrier that separates the developing grey matter into the Alar plate and Basal Plate

Question 8

Explain the differences between the Alar and Basal Plates

Answer 8

Alar Plate

 1) dorsal (posterior) side of the developing spinal cord
 2) forms sensory neurons in the brain (from neuroectoderm ------ periphery sensory are from NEURAL CREST!!!

Basal Plate

 1) ventral (anterior) side of the developing spinal cord
 2) Form motor neurons (ulnar n., radial n., etc.)

Question 9

What are the zones of the developing spinal cord and what are the cells that can be found in the?

Answer 9

Ventricular Zone (innermost)

  - Germinal/Ventricular cell
  - Ependymal cell
  - Choroid plexus cell

Intermediate Zone (GREY MATTER)

  - Astrocytes
  - Glioblasts
  - Neurons and immature neurons

Marginal Zone (WHITE MATTER) (outermost)

  - Axons
  - Oligodendrocytes

Question 10

What is the clinical importance of spinal cord positioning in newborns vs. adults

Answer 10

Newborn: Spine ends at L2 or L3
Adult: Spine ends at L1 or L2

As a person grows, their vertebral column expands but the spinal cord does not – it roots extend. So when doin a puncture, need to make sure you are lower in the lumbar in a newborn than an adult

Question 11

What does the spinal cord derive from

Answer 11

neuroectoderm

Question 12

What does Choroid-plexus cell make

Answer 12

cerebral spinal fluid

Question 13

What is the relationship between SHH and BMP

Answer 13

SHH released by notochord, BMP released by Roof Plate (on dorsal end of developing cord) and the epidermis.

Dorsal = greater [BMP]
Ventral = greater [SHH]

Balance of of the two is what gives rise to Alar and Basal plates

Question 14

What does high [BMP] lead to

Answer 14

PAX3 and PAX7 activation

sensory neurons, alar plate formation

Question 15

What does high [SHH] lead to

Answer 15

NKX2.2 and NKX6.1

Ventral neurons, basal plate

Question 16

What occurs in areas just dorsal on the high [SHH] ventral areas?

Answer 16

NKX6.1 and PAX6 are activated

ventral motor neuron formation

Question 17

What germ layers make up the PNS

Answer 17

neuroectoderm and neural crest

Question 18

What PNS cells develop from the neural tube

Answer 18

neurons of the ventral root
motor neurons
pre-ganglionic autonomic cells

Question 19

What PNS cells develop from neural crest

Answer 19

neurons of the dorsal root ganglion
sensory ganglia of cranial nerves
Schwann cells
sympathetic/parasympathetic ganglia

Question 20

What does each part of a nerve control:
    A) dorsal/posterior root
    B) ventral/anterior root
    C) dorsal/posterior ramus
    D) ventral ramus
    E) spinal nerve

Answer 20

A) sensory
B) motor
C) mixed
D) mixed
E) mixed

Question 21

Types of neurons

Answer 21

Efferent and Afferent

Efferent
somatic — end on skeletal muscle
visceral — autonomic – controls smooth muscle

Afferent
somatic – sensory fibers coming from integument
visceral — sensory fibers from viscera (organs)

Question 22

What is the vertebral location of the sympathetic NS

Answer 22

T1 - L2. (thoracic-lumbar region)

Question 23

What is the location of the parasympathetic NS and what nerves are involved

Answer 23

cranial-sacral

cranial nerves 3, 7, 9, 10
sacral nerves 2, 3, 4

Question 24

Explain the parasympathetic and sympathetic two-link chain

Answer 24

1) preganglionic (neuroectoderm) from spinal cord to sympathetic ganglia (neural crest)
2) Postganglionic fiber from ganglia to viscera (all neural crest)

preganglionic neuron is longer and postganglionic is shorter parasympathetic than sympathetic

Question 25

Where are ganglia in the parasympathetic NS located

Answer 25

the wall of viscera

Question 26

What are the four cranial ganglia of the parasympathetic NS and what do they derive from

Answer 26

1) ciliary
2) pterygopalatine
3) submandibular
4) otic

NEURAL CREST

Question 27

What are the 3 cervical, 2 thoracic and 2 lumbar ganglia of the sympathetic NS and what do they derive from

Answer 27

Cervical
      1) superior cervical ganglion
      2) middle cervical ganglion
      3) inferior cervical ganglion
Thoracic
      1) Celiac ganglion
      2) Aortico-renal ganglion
Lumbar
      1) Superior mesenteric ganglion
      2) Inferior mesenteric ganglion

ALL NEURAL CREST!!!!!

Question 28

What is the difference between Schwann cells and Oligodendrocytes?

Answer 28

Schwann cells myelinated IN THE PNS

Oligodendrocytes are in CNS

Question 29

What do preganglionic cell bodies develop from?

Answer 29

The basal plate

Question 30

Sensory neurons of the Radial n. derive from…

Answer 30

neural crest cells