Development PNS

19 important questions on Development PNS

What are the parts of the CNS and what are the parts of the PNS?

CNS: Brain + spinal cord
PNS: Cranial nerves & ganglia + Spinal nerves & ganglia + Autonomic nerves & ganglia + Enteric nervous system

What are cranial nerves?

Cranial nerves: the twelve sets of 2 branches which almost exclusively originate from the brain (and not the spinal cord).

What is a spinal nerve?

The spinal nerve is a mixed nerve from branches of the motor, sensory and autonomous systems and carry signals from CNS to periphery (sympathetic, somatic and autonomous nervous systems).
The spinal nerve starts when the dorsal and ventral tracts merge (mix of motor, sensory, and autonomous signals) and connects internal organs with the central nervous system.
  • Higher grades + faster learning
  • Never study anything twice
  • 100% sure, 100% understanding
Discover Study Smart

Spinal nerves are part of which nervous system?

Spinal nerves are part of the sympathetic nervous system: sensations in dorsal root, motor commands in ventral root.

How many pairs of spinal nerves are present in a human body?

31 pairs

What are autonomous nerves?

Autonomous nerves regulate smooth muscle, heart muscle, glands. And are therefore involved in blood pressure, bowel peristalsis, contraction bronchi, glucose levels, etc etc.

Autonomous nerves are part of which nervous system?

Autonomous nerves are part of thesympathetic (in spinalnerve) & parasympathetic (partially in cranialnerves) nervous system.

What is the enteric nervous system (ENS)?

The ENS communicates with the CNS via the vagus nerve and the sympathetic nervous system. The ENS can also function entirely independently as if it had its own "brain". It contains efferent and sensory nerve cells and interneurons and it uses more than 30 neurotransmitters, including acetylcholine, dopamine and serotonin.

What are the differences between the sympathetic and parasympathetic nervous system?

  1. Location of ganglia (sympathetic: close, parasympathetic: far)
  2. Origin of fiber bundles
  3. Neurotransmitter
  4. Sympathetic: fight or flight vs parasympathetic: rest and digest

What does develop into the CNS?

Ectoderm develops into neuroepithelium, which develops in the CNS.

What does develop into the PNS?

Ectoderm develops into neural crest & ectodermal placodes, this develops into the PNS.

Where does the sympathetic nervous system develop?

Sympathetic nervous system develops at thoracic en lumbar levels.

Where does the parasympathetic nervous system develop?

Parasympathetic nervous system develops cranial en sacral.

What does ectoderm become, what about mesoderm and endoderm?

Ectoderm becomes the CNS and PNS.
Mesoderm becomes the muscles/skeleton.
Endoderm becomes needed for digestion, breathing, and the urinary tract.

What are the steps of development of the PNS?

  1. Formation sympathetic ganglia in week 5
  2. Somatic motorneurons bundle together and form the ventral root (day 30)
  3. Somatic, autonomous and sensory fibers bundle together form the spinal nerves   
  4. Development of “sympathetic chain ganglia” 
  5. The axonal tracts grow from the “sympathetic chain ganglia” towards their peripheral target organs   

The development of motor and sensory neurons is organized in dermatomes (somatic innervation is organized in segments). What is a dermatome?

A “dermatome” can be described as body segment.
Each dermatome is innervated by sensory fibers of 1 spinal nerve although there is partial overlap between adjacent dermatomes.

What happens during the first step of PNS development, formation sympathetic ganglia?


  • Neuronal migration from neural crest
  • Emergence of “bilateral chain” of sympathetic ganglia
  1. Additional migration to facilitate development of prevertebral ganglia (collateral ganglia – lower abdomen)
  2. Additional migration to facilitate development of sympathetic organ plexi (heart, lungs and enteric system)

What happens during the third step of PNS development, somatic, autonomous and sensory fibers bundle together form the spinal nerves?

From the DRG, bipolar neurons begin to grow towards both spinal cord and the ventral cord (this happens when the ventral motor neurons approach the DRG). This creates the dorsal strand. The bipolar neurons grow in the dorsal horn and make connections with interneurons in the spinal cord, which in turn make contact with somatic motor neurons.

What happens during the fourth step of PNS development, development of sympathetic chain ganglia?

The spinal nerve continues to grow into the sympathetic chain ganglia. Here this (preganglionic) axon can make contact with a postganglionic neuron. This post-ganglionic neuron grows out and connects to the peripheral organ.

The question on the page originate from the summary of the following study material:

  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo