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MBBS II HNNS > L2 – Peripheral Nervous System (PNS) > Flashcards

L2 – Peripheral Nervous System (PNS) Flashcards

1
Q

List the functional divisions of the peripheral nervous system.

A
  1. Sensory division
    a) Visceral sensory division
    b) Somatic sensory division
  2. Motor division
    a) Somatic motor
    b) Visceral motor&raquo_space; Sympathetic and Parasympathetic
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2
Q

What does the PNS consist of?

A
  • nerve fibres and nerve ganglia outside the brain: spinal nerves and cranial nerves (except CNII)
  • special nerve ending
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3
Q

What type of nerves and ganglia make up the PNS?

A

Cranial nerves and ganglia (except Optic nerve)

Spinal nerves and ganglia

Autonomic nerves and ganglia

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4
Q

List the 12 cranial nerves.

A
  1. Olfactory
  2. Optic
  3. Oculomotor
  4. Trochlear
  5. Trigeminal
  6. Abducent
  7. Facial
  8. Vestibulocochlear
  9. Glossapharyngeal
  10. Vagus
  11. Accessory
  12. Hypoglossal
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5
Q

Total number and divisions of spinal nerves?

A

31 pairs of spinal nerves

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

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6
Q

List the plexuses formed by spinal nerves?

A
  • Cervical plexus: C1-C4
  • Brachial plexus: C5-T1
  • Lumbar plexus: T12/L1-L4
  • Sacral plexus: L4-S4
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7
Q

Describe the structure of spinal nerves.

A

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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8
Q

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

A 
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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9
Q

Describe the overall route of somatic MOTOR efferent system?

A

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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10
Q

Describe the organization of somatic sensory (afferent) system?

A

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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11
Q

Higher centre and presynaptic outflow of the sympathetic nervous system?

A

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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12
Q

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

A

Higher centre = hypothalamus

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

Long Pre- GN, Short Post- GN

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13
Q

Number and divisions of paravertebral ganglia?

A

3 cervical ganglia

12 thoracic ganglia

4 lumbar ganglia

4-5 sacral ganglia

1 Ganglion impar (links 2 sympathetic trunks)

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14
Q

List the major prevertebral ganglia/ plexuses?

A

Celiac ganglia

Aorticorenal ganglion

Superior mesenteric ganglia

Inferior mesenteric ganglia

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15
Q

What are the 2 presynaptic sympathetic ganglia systems?

A

Paravertebral and Prevertebral ganglia

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16
Q

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

A

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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17
Q

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

A

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

18
Q

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

A

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

19
Q

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

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

All other splachnic nerves carry presynaptic sympathetic fibers

20
Q

How do paravertebral ganglia connect with prevertebral ganglia?

A

via Splanchnic nerve routes

21
Q

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

A

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

22
Q

List the splanchnic nerves below T5?

A 
Greater s.n. 
Lesser s.n.
Least s.n.
Lumbar s.n. 
Sacral s.n.
Pelvic s.n.
23
Q

Outflow route of sympathetic fibers in Greater splanchnic nerves?

A

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

24
Q

Outflow route of sympathetic fibers in Lesser splanchnic nerves?

A

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

25
Q

Outflow route of sympathetic fibers in Least splanchnic nerves?

A

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

26
Q

Outflow route of sympathetic fibers in Lumbar splanchnic nerves?

A

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

27
Q

Outflow route of sympathetic fibers in Sacral splanchnic nerves?

A

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

28
Q

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

A

Pelvic Splanchnic nerve

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

29
Q

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

A

Above T5, splanchnic nerves carry sym. fibers to:

  • Carotid plexus
  • Cardiac and Pulmonary plexuses
30
Q

Trace the sympathetic innervation of Chromaffin cells.

A

Chromaffin cells (medullary cells) act as postsynaptic neurones

Spinal nerve&raquo_space; paravertebral ganglia&raquo_space; greater, lesser or least splanchnic nerve&raquo_space; celiac/ renal plexus&raquo_space; Chromaffin cells

31
Q

List all the nerves that carry parasympathetic fibers?

A

Cranial nerves III, VII, IX, X

Pelvic splanchnic nerves

All carry presynaptic fibers
(Para- long- pre)

32
Q

List the parasympathetic ganglia of the head and neck?

A

•Ciliary ganglion

•Pterygopalatine
ganglion

•Submandibular
ganglion

•Otic ganglion

33
Q

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

A

CN III&raquo_space; Ciliary ganglion

CN VII&raquo_space; Pterygopalatine and Submandibular ganglion

CN IX&raquo_space; Otic ganglion

34
Q

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

A

False

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

35
Q

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

A

False

Enteric NS does not arise from brain stem or spinal cord

Contains own afferent, efferent and interneurons for independent reflex arc and operation

36
Q

List the plexuses in the enteric nervous system?

A

Myenteric (Auerbach’s) plexus

Submucosal (Meissner’s) plexus

37
Q

Describe the gross structure and layers of nerve fibers?

A

Axon and myelin sheath wrapped by endoneurium

Nerve fascicles wrapped by perineurium

Nerve trunk wrapped by Epineurium

38
Q

What are the glial cells in PNS?

A

Schwann cells

Perineuronal satellite cells

39
Q

Function of the 2 glial cells in PNS?

A

Schwann cells form myelin sheath

Perineuronal satellite cells surround soma, controlling microenvironment, provide electrical insulation and metabolic exchanges

40
Q

Difference between neuropathy and Neuritis?

A

Neuropathy = pathological damage to neuron and myelin sheath causing functional disturbance

Neuritis = inflammation of the PNS

41
Q

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

A

Increasing severity:

Neuropraxia > Axontmesis > Neurotmesis

42
Q

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

A
  • 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

MBBS II HNNS (57 decks)

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