Development of PNS

Question 1

Neurulation

What is the Rostral Neuropore?

What is the Caudal Neuropore?

Where does the neural tube split production for brain and spinal cord?

Answer 1

The cranial open end of the neural tube

The caudal open end of the neural tube

Caudal to 4th Somite = Spinal Cord

Question 2

Divisions of the Nervous System

What makes up the CNS?

What makes up the PNS?

What are the divisions of PNS?

Answer 2

Brain & Spinal Cord

Cranial Nerves, Spinal Nerves, Ganglia, Enteric Plexus, Sensory Receptors

Somatic (Voluntary) & Autonomic (Involuntary) - Parasympathetic/Sympathetic

Question 3

Gray Matter of Spinal Cord

What is located in Gray Matter? Myelination status?

Areas of Gray Matter?

Answer 3

Cell bodies of Neurons (Not Myelinated)

Dorsal Horn: Sensory/Afferent

Lateral Horn: Autonomics (T1-L2)

Ventral Horn: Motor/Efferent

Question 4

White Matter of Spinal Cord

What is located in White Matter? Myelination status?

Names of areas of White Matter?

Answer 4

Location of Axons (Myelinated)

Dorsal Funiculus: Sensory

Lateral Funiculus: Sensory/Motor

Ventral Funiculus: Motor

Question 5

Formation of Spinal Cord

What are the Plates of the Neural Tube and what type of neurons are in each?

What divides the plates?

What is the name of the central canal?

What are the Zones of the Spinal Cord during development?

Answer 5

• Plates:
  
  • Alar Plate: Sensory Neurons within CNS
  • Basal Plate: Motor Neurons
• Sulcus Limitans
• Neural Canal
• Zones:
  
  • Ventricular Zone
  • Intermediate Zone (Mantle Layer) - Gray Matter
  • Marginal Zone - White Matter

Question 6

Spinal Cord Zones

What Cells are in the Ventricular Zone?

What Cells are in the Intermediate Zone (Gray Matter)?

What Cells are in the Marginal Zone (White Matter)?

Where do Microglial Cells come from?

Answer 6

Stem Cells –> Ependymoblast –> Ependymal Cell or Choroid Plexus Cell (CSF Production)

Astrocyte; Neuron Cell Bodies

Oligodendrocyte; Neuron Axons

Mesoderm (Mesenchymal Cell –> Microglial Cell)

Question 7

What is the position of the spinal cord in newborns and adults?

What do Neural Crest Cells give rise to?

Answer 7

Newborn: L2 or L3

Adult: L1 or L2

Spinal Ganglion cells (DRG) and Sensory Neurons in periphery

Question 8

The Dorsal (Sensory) and Ventral (Motor) regions of the SC are dependent on what during development?

Roof Plate and Neuroectoderm release what and what is activated to produce Sensory Neuron differentiation forming the Alar Plate?

Notochord and Floor Plate release what and what is activated to produce Ventral/Motor Neuron formation forming the Basal Plate?

Dorsal to the Floor Plate, there are varied levels of what that activate what?

Answer 8

Concentration Gradients

High BMP levels activate PAX3 and PAX7

High SHH levels activate NKX2.2 and NKX6.1

Slightly lower SSH and higher levels of BMP activating NKX6.1 and PAX6 (Ventral Motor Neurons)

Question 9

Development of PNS

What forms the PNS? (2)

Neurons that develop from the Neural Tube are what?

Neurons that develop from Neural Crest include what?

Answer 9

Neural Crest and Ectodermal Placode

Motor Neurons

Neurons of DRG, Sensory Ganglia of Cranial Nerves, Schwann Cells, Sympathetic/Parasympathetic Ganglia

Question 10

Dorsal Ramus provides Motor and Sensory nerves to what type of muscles?

Ventral Ramus provides Motor and Sensory nerves to what type of muscles?

Answer 10

Epimere

Hypomere

Question 11

Neuroectoderm (Motor Neurons)

GSE

GVE

SVE

Neural Crest (Sensory Neurons)

GSA

GVA

Answer 11

• GSE: General Somatic Efferent - Somatic Muscles arising from Somites (End on skeletal muscle)
• GVE: General Visceral Efferent: Autonomics to smooth and cardiac muscles and glands (End on autnomic ganglion cells)
• SVE: Special Visceral Efferent: Muscles derived from Pharyngeal Arches
• GSA: General Somatic Afferent: Sensory in skin, joint capsule, tendon, muscle
  
  • Located in Ectoderm - or derived adjacent to ectoderm
• GVA: General Visceral Afferent: Sensory of Visceral Structures
  
  • Located in Endoderm - or derived adjacent to endoderm

Question 12

Autonomic Nervous System

Innervation of what?

Two Motor Paths

Neural Crest responsible for formation of what?

Neuroectoderm responsible for formation of what?

Answer 12

Smooth Muscle, Cardiac Muscle, Glands

Sympathetic and Parasympathetic

Ganglia and Post-Ganlgion Cells

Pre-Ganglion Cells

Question 13

Sympathetic Autonomic System

Location?

Two Link Chain System

Answer 13

Spinal Cord in Thoraco-Lumbar Region (T1-L2)

Short Preganglionic Neuron (Myelinated) from Spinal Cord (NE) to Autonomic Ganglia

Long Postganglionic Neuron (Unmyelinated) from Ganglia to Viscera

Question 14

Parasympathetic Autonomic System

Location?

Two Link Chain System

Where are the Ganglia located?

Answer 14

Cranial - Sacral Region (Cranial Nerves & 2nd-4th Sacral Spinal Nerves (GVE))

Long Preganglionic Neuron (Myelinated) from Spinal Cord to Autonomic Ganglia

Short Postganglionic Neuron (Unmyelinated) from Ganglia to Viscera

Usually in wall of viscera; 4 Cranial Ganglia

Question 15

Myelination

What provides myelination in CNS? Where and when does it start?

What provides myelination in PNS? What is myelinated first and when?

Answer 15

Oligodendrocytes: Starts in lower brain stem (6th month through puberty)

Schwann Cells: Motor Roots before Sensory Roots (4th Month)