Uploaded July 2022 | Updated September 2026, 2 weeks ago

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Content:
0:00 Introduction
00:59 What is Considered the PNS?
02:05 How to Classify the PNS
05:52 Damage to Motor Neurons
08:03 Spinal Nerve
08:50 External Scheme of the Spinal Nerve
13:05 Internal Scheme of Spinal Nerve
16:25 Posterior Branch of Spinal Nerve
17:55 Anterior Branch of Spinal Nerve


What is the Peripheral Nervous System?
- Cranial Nerves 12 nerve pairs
- Spinal Nerves 31 nerve pairs

Classification of the PNS
- Sensory System
○ Soamtic Sensory Fibers
○ Visceral Sensory Fibers
○ Exteroreceptors, Proprioreceptors, Periosteum
- Motor System
○ Somatomotor System (Somatic system)
§ Voluntary control
○ Autonomic Nervous System / Visceromotor nervous system
§ Sympathetic Nervous System (C8-L2 Lateral horn)
§ Parasympahetic Nervous System (S2-S4 Lateral horn)
§ Enteric Nervous System (myenteric and submucosal plexuses in walls of digestive organs)

Clinical Significance
- Lower Motor Neuron damage
○ Located in anterior horn of spinal cord and nuclei of cranial nerves
○ Damage to lower motor neurons:
○ Flaccid Paralysis
○ Hypotonia
○ Paresis/Plegia
○ Hyporeflexia / areflexia
- Upper Motor Neuron damage
○ May rise after a stroke or a perinatal hypoxia
○ Spastic Paralysis
○ Paresis / Plegia
○ Hypertonia
○ Hyperreflexia
○ Babinski's sign

External Scheme of Spinal Nerve
- Rootlets (fila radicularia)
○ Anterior root (radix anterior)
○ Posterior root (radic posterior)
§ Spinal Ganglion (ganglion sensorium nervi spinalis)
- Trunk of Spinal Nerve (truncus nervi spinalis)
○ Posterior Branch (Ramus posterior)
○ Anterior Branch (ramus anterior)
○ Meningeal branch (ramus meningeus)
○ Ganglion of sympathetic trunk (ganglion trunci sympathici)
○ Gray ramus communicans
○ White ramus communicans (ramus communicans albus)

Internal Scheme of Spinal Nerve
- Somatomotor fibers
- Pre-ganglionic sympathetic fibers (Visceromotor fibers)
- Post-ganglionic Fibers
- Pre-ganglionic parasympathetic fibers
- Somatosensory fibers
- Viscerosensory fibers (baroreceptors, chemoreceptors, unspecific organ senstation)

Posterior Branch:
- Suboccipital Nerve (nervus suboccipitalis) C1
- Greater Occipital Nerve (nervus occipitalis major) C2
- Occipital Nerve (nervus occipitalis tertius) C3
- Superior Clunial Nerve (Nervi Clunium Superiores) L1-L3
- Middle Clunial Nerves (Nervi Clunium Medii) S1-S3

Anterior Branch:
- Cervical Plexus (Plexus cervicalis) C1-C4
- Brachial Plexus (Plexus brachialis) C4-T1
- Thoracic Nerves (Nervi thoracici) T1-T12
- Lumbar Plexus (Plexus Lumbalis) T12-L4
- Sacral Plexus (Plexus Sacralis) L4-S4