15. Development of the PNS Flashcards
If something is going to go wrong during development when will it most likely take place?
Weeks 3-8 are the critical period
What are the 2 major divisions of the nervous system?
Central Nervous System (CNS)
- Brain
- Spinal Cord
Peripheral Nervous System (PNS)
- Cranial nerves
- Spinal nerves
- Ganglia
- Enteric plexus
- Sensory receptors
Describe the gray matter of the spinal cord
- Location of cell bodies of neurons
- Dorsal (posterior) horn: sensory
- Lateral horn: autonomics
- Anterior (ventral) horn: motor
Describe the white matter of the spinal cord
- Location of axons
- Dorsal (posterior) funiculus: sensory
- Lateral funiculus: sensory and motor
- Anterior (ventral) funiculus: primarily motor
Somatic vs Autonomic nervous system
Somatic:
- voluntary control
- skeletal muscle contration
- to the body (Median N)
Autonomic:
- involuntary control
- parasympathetic/Sympathetic
- smooth muscle
- cardiac muscle
- glands
Describe the structures fo the Sulcus Limitans
Alar Plate: sensory neurons
Basal Plate: motor neurons
Where is the neural tube located in relation to somites?
Caudal to 4th pair of somites
What are the 3 zones of the central canal or neural canal?
- Ventricular Zone
- choroid plexus
- ependymal cell
- ependymoblast
- germinal or ventricular cell - Intermediate Zone (mantle layer) (gray matter)
- neuron
- glioblast
- radial glial cell
- astrocyte - Marginal Zone (white matter)
- oligodendrocyte
- Everything is Ectoderm
- Microglial and mesenchymal cells are coming from mesoderm
What is the position of the spinal cord in a newborn vs an adult?
Newborn: L2 or L3
Adult: L1 or L2
_________ cells give rise to spinal ganglion cells and sensory neurons in the periphery
Neural crest
What are the concentration gradients that form the spinal cord?
Dorsal (sensory) and ventral (motor) region dependent on concentration gradients
Dorsal: High BMP levels activate PAX3 and PAX7 = sensory neuron differentiation = alar plate
Ventral: High SHH levels activate NKX2.2 and NKX6.1 = ventral neuron formation = basal plate
- (Just dorsal there are slightly lower SSH and higher levels of BMP activate NKX6.1 and PAX6 = ventral motor neurons)
Describe the development of the PNS
The neural crest and ectodermal placode
form the PNS
Cells that develop from the neural tube
include: (neuro ectoderm)
- motor neurons
- pre-ganglionic autonomic neurons
Cells that develop from the neural crest include: (neural crest)
- Neurons of dorsal root ganglia
- Sensory ganglia of cranial nerves
- Schwann cells
- Sympathetic ganglia
Describe a typical segmental nerve
• Dorsal root (sensory)
– Spinal ganglion (dorsal root ganglion)
- Ventral root (motor)
- Spinal nerve (mixed)
• Dorsal ramus (mixed)
– Motor to dorsal muscles
– Sensory to dorsal integument
• Ventral ramus (mixed)
– Motor to limbs, lateral and ventral body wall
– Sensory to integument of same regions
• Ramus communicantes
– Motor and sensory to viscera
What are the general characteristics of Afferent neurons?
Afferent (sensory) (Neural crest) – Somatic: Sensory fibers originating chiefly from integument – Visceral: Sensory fibers originating from viscera
What is the autonomic nervous system?
• Innervation of smooth muscle, cardiac muscle and glands.
• Consists of two motor paths
– Sympathetic
– Parasympathetic
- Neural crest- formation of ganglia and post-ganglion cells.
- Neuroectoderm – formation of the pre-ganglion cells
What is the sympathetic nervous system?
Located in the spinal cord in the thoraco-lumbar region
Two link chain:
– Preganglionic from spinal cord to sympathetic ganglia
– Postganglionic fiber from ganglia to viscera
What is the sympathetic nervous system?
Located in the spinal cord in the thoraco-lumbar region
(T1-L2/3) (lateral horn)
Two link chain:
– Preganglionic from spinal cord to sympathetic ganglia (myelinated)
– Postganglionic fiber from ganglia to viscera (un-myelinated)
List the major sympathetic ganglia listed in class
Superior, Middle and Inferior Cervical ganglion come from neural crest
Prevertebral Ganglia (sympathetic ganglia)
- Celiac ganglion
- aortic or renal ganglion
- superior and inferior mesenteric ganglion
What is the parasympathetic nervous system?
Parasympathetic
• Cranial-sacral region
– Cranial: primarily cranial nerves (3, 7, 9, 10)
– Sacral: 2nd to 4th sacral spinal nerves (GVE)
• Neural crest components
• Two link chain
– Preganglionic from spinal cord to sympathetic ganglia
– Postganglionic fiber from ganglia to viscera
• Ganglia
– Usually in wall of viscera
– Four cranial ganglia
Give some examples of parasympathetic ganglia
- Ciliary
- Otic
- Submandibular
- Ptergopalatine
Describe the myelination of CNS and PNS neurons
Form during late fetal period
• Continue into first postnatal year
• CNS: oligodendrocytes
– Starts in lower brain stem
• Older tracts first
– 6th month through puberty
• PNS: Schwann cells
– Motor roots myelinated before sensory roots
– 4th month
Sensory neurons of the radial nerve are derived from:
A. Neural crest cells
B. Basal lamina cells
C. Alar lamina cells
D. Surface ectoderm
A. Neural crest cells
Which of the following cells is not derived from the ventricular zone of the neural tube?
A. Oligodendrocyte B. Astrocyte C. Schwann cell D. Ependymoblast E. Glioblast
C. Schwann cell
Which of the following are basal lamina derivatives?
A. Spinal cord sensory neurons
B. Spinal cord motor neurons
C. Spinal ganglia
D. Dorsal root
B. Spinal cord motor neurons
The caudal neuropore normally closes in which week of the fertilization calendar?
A. Week 2 B. Week 3 C. Week 4 (1st month) D. Week 8 (2nd month) E. Week 12 (3rd month)
C. Week 4 (1st month)
The myelin sheaths of axons in the central nervous system are formed by:
A. Microglia B. Oligodendrocytes C. Astrocytes D. Schwann cells E. Ependymal cells
B. Oligodendrocytes
Preganglionic sympathetic cell bodies develop from:
A. Neural crest
B. Mesoderm
C. Alar plate
D. Basal plate
D. Basalplate
Postganglionic parasympathetic cell bodies develop from:
A. Neural crest
B. Mesoderm
C. Alar plate
D. Basal plate
A. Neural crest
