L2 – Peripheral Nervous System (PNS) Flashcards by Max Kam

List the functional divisions of the peripheral nervous system.

Sensory division
a) Visceral sensory division
b) Somatic sensory division
Motor division
a) Somatic motor
b) Visceral motor&raquo_space; Sympathetic and Parasympathetic

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What does the PNS consist of?

nerve fibres and nerve ganglia outside the brain: spinal nerves and cranial nerves (except CNII)
special nerve ending

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What type of nerves and ganglia make up the PNS?

Cranial nerves and ganglia (except Optic nerve)

Spinal nerves and ganglia

Autonomic nerves and ganglia

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List the 12 cranial nerves.

Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducent
Facial
Vestibulocochlear
Glossapharyngeal
Vagus
Accessory
Hypoglossal

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Total number and divisions of spinal nerves?

31 pairs of spinal nerves

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

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List the plexuses formed by spinal nerves?

Cervical plexus: C1-C4
Brachial plexus: C5-T1
Lumbar plexus: T12/L1-L4
Sacral plexus: L4-S4

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Describe the structure of spinal nerves.

Dorsal root = sensory
Ventral root = motor

2 roots fuse together to make spinal nerve

Afferent sensory neuron from body’s periphery synapse at dorsal root ganglia to reach CNS via secondary sensory neuron

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List the cranial nerve sensory ganglia. Not every cranial nerve has a ganglion

5 = Trigeminal ganglion 
7 = Geniculate ganglion 
8 = Spiral ganglion + Vestibular ganglion 
9 = Superior (jugular) ganglion + Inferior (petrosal) ganglion 
10 = Superior (rostral) ganglion + Inferior (nodose) ganglion

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Describe the overall route of somatic MOTOR efferent system?

Cell bodies of motor system are located in the CNS (brain stem/ Ventral horn spinal cord)

Axons form nerve bundle in the PNS

Terminates at skeletal muscles via NMJ

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Describe the organization of somatic sensory (afferent) system?

Primary cell bodies of sensory system located in the PNS ganglia

Axons divided into CENTRAL and PERIPHERAL axons (all pseudounipolar neurons with 2 roots)

CENTRAL axon: projects to CNS and forms secondary sensory neuron within CNS

PERIPHERAL axon: connects with peripheral organs to form sensory endings

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Higher centre and presynaptic outflow of the sympathetic nervous system?

Higher centre = hypothalamus

Presynaptic outflow = located in the intermediolateral cell column (lateral horn) of the T1 - L2/3 spinal cord&raquo_space; sympathetic ganglia

Short Pre-GN, Long Post-GN

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Higher centre and presynaptic outflow of the parasym. nervous system?

Higher centre = hypothalamus

Presynaptic outflow
= located in the brain stem + S2-S4 spinal cord

Long Pre- GN, Short Post- GN

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Number and divisions of paravertebral ganglia?

3 cervical ganglia

12 thoracic ganglia

4 lumbar ganglia

4-5 sacral ganglia

1 Ganglion impar (links 2 sympathetic trunks)

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List the major prevertebral ganglia/ plexuses?

Celiac ganglia

Aorticorenal ganglion

Superior mesenteric ganglia

Inferior mesenteric ganglia

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What are the 2 presynaptic sympathetic ganglia systems?

Paravertebral and Prevertebral ganglia

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Describe the outflow of presynaptic sympathetic fibers from spinal nerves TOWARDS the paravertebral ganglia?

Spinal nerves interconnect with paravertebral ganglia via communicating rami (consists of white and gray rami)

White communicating ramus (only presents from T1 to L2/3) carries small myelinated presynaptic fibres from lateral horn to the sympathetic trunk

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Describe the function of the gray communicating ramus in paravertebral ganglia?

Gray communicating ramus carries unmyelinated postsynaptic fibres from the ganglion back to the spinal nerve

What are the routes for sympathetic fibers to exit the paravertebral ganglia? (3)

1) Presynaptic synapse directly with the corresponding paravertebral ganglia&raquo_space; postsynaptic fibers through gray communicating ramus&raquo_space; spinal nerve&raquo_space; exit at that level
2) Presynaptic travel within the sympathetic trunk to reach above T1 or below L2/3&raquo_space; synapse with the paravertegral ganglia at that level&raquo_space; gray communicating ramus&raquo_space; exit
3) Pass through sympathetic trunk without synapse&raquo_space; Pre-synaptic fibers directly leave via SPLANCHNIC NERVES&raquo_space; Prevertebral ganglia

Splanchnic nerves towards Cardiac and pulmonary plexuses are exceptions: they carry Post-synaptic fibers

Which splanchnic nerves are exceptions and carry POSTsynaptic sympathetic fibers to organ?

Cardiac and pulmonary plexuses/ carotid plexuses
Minor parts of sacral splanchnic n.

All other splachnic nerves carry presynaptic sympathetic fibers

How do paravertebral ganglia connect with prevertebral ganglia?

via Splanchnic nerve routes

Difference in the sympathetic fibers carried in splachnic nerves above and below T5? (check)

Above T5: Synapse at the paravertebral ganglia first&raquo_space; Postsynaptic fibers carried inside splanchnic n.

Below T5: No synapse at the paravertebral ganglia&raquo_space; splanchnic n. carry Presynaptic fibers

List the splanchnic nerves below T5?

Greater s.n. 
Lesser s.n.
Least s.n.
Lumbar s.n. 
Sacral s.n.
Pelvic s.n.

Outflow route of sympathetic fibers in Greater splanchnic nerves?

Sympathetic presynaptic fibres, T5 - T9/10, to celiac plexus

Outflow route of sympathetic fibers in Lesser splanchnic nerves?

Sympathetic presynaptic fibres, T10 T11, to abdominal aortic plexus/renal plexus

Outflow route of sympathetic fibers in Least splanchnic nerves?

Sympathetic presynaptic fibres, T12, to abdominal aortic plexus/renal plexus

Outflow route of sympathetic fibers in Lumbar splanchnic nerves?

Sympathetic presynaptic fibres, L1-L2, to abdominal aortic plexus/ hypogastric plexuses

Outflow route of sympathetic fibers in Sacral splanchnic nerves?

Sympathetic fibres mostly presynaptic, from sacral part of sympathetic trunk to inferior hypogastric plexus

Which splanchnic nerve below T5 carry different fibers to the rest?

Pelvic Splanchnic nerve Carry Parasympathetic presynaptic fibres, from S2-S4 spinal nerves to terminal ganglia at viscera

Above T5, splanchnic nerves connect paravertebral ganglia with which prevertebral ganglia?

Above T5, splanchnic nerves carry sym. fibers to: - Carotid plexus - Cardiac and Pulmonary plexuses

Trace the sympathetic innervation of Chromaffin cells.

Chromaffin cells (medullary cells) act as postsynaptic neurones Spinal nerve >> paravertebral ganglia >> greater, lesser or least splanchnic nerve >> celiac/ renal plexus >> Chromaffin cells

List all the nerves that carry parasympathetic fibers?

Cranial nerves III, VII, IX, X Pelvic splanchnic nerves All carry presynaptic fibers (Para- long- pre)

List the parasympathetic ganglia of the head and neck?

•Ciliary ganglion •Pterygopalatine ganglion •Submandibular ganglion •Otic ganglion

List the cranial nerve supply of the head and neck parasympathetic ganglia?

CN III >> Ciliary ganglion CN VII >> Pterygopalatine and Submandibular ganglion CN IX >> Otic ganglion

The colon receives parasympathetic innervation from the vagus only. True or False?

False Proximal 2/3 = Vagus Distal 1/3 = Sacral outflow via Pelvic Splanchnic nerves

The enteric nervous system relies solely on autonomic nervous system innervation for function. True or False?

False Enteric NS does not arise from brain stem or spinal cord Contains own afferent, efferent and interneurons for independent reflex arc and operation

List the plexuses in the enteric nervous system?

Myenteric (Auerbach’s) plexus Submucosal (Meissner’s) plexus

Describe the gross structure and layers of nerve fibers?

Axon and myelin sheath wrapped by endoneurium Nerve fascicles wrapped by perineurium Nerve trunk wrapped by Epineurium

What are the glial cells in PNS?

Schwann cells Perineuronal satellite cells

Function of the 2 glial cells in PNS?

Schwann cells form myelin sheath Perineuronal satellite cells surround soma, controlling microenvironment, provide electrical insulation and metabolic exchanges

Difference between neuropathy and Neuritis?

Neuropathy = pathological damage to neuron and myelin sheath causing functional disturbance Neuritis = inflammation of the PNS

What are the stages in Seddon’s Classification of Peripheral Nerve Injuries?

Increasing severity: Neuropraxia > Axontmesis > Neurotmesis

Define each stage of the Seddon’s Classification of Peripheral Nerve Injuries ?

- Neuropraxia: injury without any anatomical discontinuity but resulting in functional disruption (nerve concussion) - Axonotmesis: microscopic division of nerve fibres (axons) without obvious discontinuity of the nerve sheath/ epineurium - Neurotmesis: complete anatomic division of the nerve fibres with obvious discontinuity of the nerve sheath/ epineurium