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Neurology > The PNS > Flashcards

The PNS Flashcards

1
Q

What can the peripheral nervous system be split into and what is its function

A 
Sensory (Afferent) and motor (efferent) 
Motor - autonomic and somatic 
autonomic - sympathetic and parasympathetic
Communication between the CNS and body
Movement and involuntary response
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2
Q

How many nerves does the PNS consist of

A 
43 pairs
12 cranial
31 spinal 
(8 cervical
12 thoracic
5 lumbar
1 sacral
1 coccygeal)
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3
Q

Describe neuropraxia

A

Reversible conduction block
Demyelination. Axon intact. Endoneurium + connective tissue intact
E.g nerve compression

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4
Q

What distinguishes C1-7 from the other spinal nerves

A

They arise above their corresponding vertebra and do not always have mixed motor and sensory function

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5
Q

Describe axontomesis

A

Degeneration below and proximal to lesion. Nerve regrowth possible. Epineurium and perineurium intact
Demyelination. Axon loss. Connective tissue intact

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6
Q

Give differences in structure of the somatic, autonomic and sensory neurones

A

somatic - one neurone that transmits straight from the CNS to the effector site e.g. skeletal muscle
Autonomic - pre-ganglionic neurone, ganglion, and post ganglionic neurone to effector site e.g. vessels
sensory - one ganglion with a split axon from skin receptor to CNS

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7
Q

Where may sensory information arise from and how does it travel to the brain

A 
conscious and visceral areas 
1. periphery
2. dorsal root ganglion
3. brainstem/spinal cord
Always stimulatory 
Uses ACh
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8
Q

Describe neurotmeses

A

Complete nerve division and disruption, no nerve growth
Demyelination. Axon loss. Connective tissue damaged- damage to epineurium
E.g laceration

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9
Q

What is somatic and visceral

A

somatic - skin and muscle

visceral - internal organs and glands

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10
Q

What is the somatic nervous system made up of

A

2 neurons, the upper motor neurone (CNS) and the lower motor neurone (PNS)

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11
Q

What is the role of the somatic nervous system

A

Efferent nerves
Voluntary control over skeletal muscle
voluntary or automatic

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12
Q

Describe the development of the somatic nervous system

A

The lower motor neurons originate form the basal plate
Multipolar neuron from the spinal cord innervate muscle fibres
One motor neuron will innervate many muscle fibres

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13
Q

What is the autonomic nervous system made up of

A

Efferent nerves and ganglia that stimulate effectors outside control e.g. heart rate
Involuntary effectors e.g. heart smooth muscle, glands

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14
Q

What can the autonomic nervous system be split into

A

Parasympathetic or sympathetic

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15
Q

Describe the autonomic pathway

A
  1. Hypothalamus
  2. Brainstem (parasympathetic) /spinal cord (sympathetic)
  3. Preganglionic neurone (myelinated)
  4. Ganglion (unmyelinated)
  5. Effector organ
    Stimulatory or inhibitory
    ACh or NA
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16
Q

Describe the somatic pathway

A
  1. Primary motor cortex
  2. Brainstem/ psinal cord
  3. NMJ
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17
Q

Describe the development of the autonomic nervous system

A

All derived from neural crest cells

Unmyelinated C fibres

18
Q

What is a ramus

A

A division/ branch of a nerve

Motor and sensory nerves that exit form the roots

19
Q

Describe the basic anatomy of the peripheral nervous system from the spinal cord

A

Adheres to the spinal cord via rootlets
dorsal (posterior) and ventral (anterior) roots
dorsal root ganglion
dorsal and ventral ramus of the spinal nerve

20
Q

Which ramus from the spinal cord is the intercostal nerve

A

Ventral ramus of the spinal nerve

21
Q

Where are the roots of the splanchnic nerve found

A

The tip of the sympathetic chain ganglion

22
Q

What is the difference between ventral and dorsal root

A

ventral - somatic and autonomic motor neurones (Efferent)

dorsal - somatic and autonomic sensory neurones (afferent), cell bodies in the dorsal root ganglion

23
Q

What is a spinal nerve

A

The motor and sensory neurones of that spinal segment

24
Q

What is the difference between dorsal and ventral rami

A

ventral - motor and sensory nerves innervating the rest of the body from the neck down
dorsal - motor and sensory nerves innervating the skin and back + deep back muscles

25
Q

What is the difference between the ventral and dorsal horn of grey matter

A

ventral - somatic motor neurones (efferent)

dorsal - somatic and autonomic sensory neurones

26
Q

Describe the embryology of the PNS and CNS

A

PNS - neural crest

CNS - neuroepithelium, wall of the neural tube

27
Q

Describe peripheral nerve structure

A

Nerve surrounded by the epineurium
Bundle of neurones (fasicle) is surrounded by the perineurium
Neurone is surrounded by the endoneurium

28
Q

Which factors increase conduction velocity

A

Myelination
Increased diameter (less resistance)
Increased temp.

29
Q

How does stimulus strength affect propagation speed

A

No effect

30
Q

Which neurones are responsible for sensing temperature

A

C fibres

31
Q

How are neurones groupes

A

based on conduction and diameter

32
Q

Compare the different groups of neurones

A

A fibres : myelinated, large diameter somatic
B fibres : myelinated, small diameter, viscera
C fibres : unmyelinated, small diameter, somatic and visceral pain afferents, cytoplasm of the Schwann cell only (neurilemma)

33
Q

What is the order of conduction velocity in the different neurone groups

A

A>B>C

34
Q

What is nerve plexus

A

Networks of successive ventral rami that exchange fibres (e.g. cervical, brachial plexus)
Mainly innervate the limbs
Thoracic ventral rami do not form nerve plexuses

35
Q

What is a dermatome

A

Areas of skin supplied by a single sensory spinal nerve root. Skin is continuous
Can determine the site of spinal damage
Stacked along the thorax and abdomen longitudinally around the limbs

36
Q

What is a myotome

A

Muscles that are supplied by a single motor spinal nerve root

37
Q

How can distributions of sensory innervation be classified

A

Dermatomal Innervation – The strip of skin supplied by a pair of spinal nerves is referred to as a dermatome (e.g. L2 to anterior thigh)
Peripheral Innervation – The area of skin supplied by a single peripheral nerve (e.g. femoral nerves cutaneous branches to anterior thigh)

38
Q

Which plexus innervates the upper and lower limbs

A

Upper limb - Brachial plexus Ventral rami C5-T1

Lower limbs - Lumbosacral Ventral rami L1-S3

39
Q

Describe peripheral neuropathies

A

Damage or disease affecting PNS nerves
Mononeuropathy- single nerve being affected
Polyneuropathy - several nerves being affected

40
Q

What are the causes of neuropathies

A 
Metabolic
Toxic
Inflammatory
Traumatic
Genetic
Idiopathic - 30%
41
Q

What is the effect of neuropathies

A

May impair sensation, movement, gland or organ function
Sensory nerves - cause tingling, pain, numbness
Motor nerves - cause weakness to hands and feet
Autonomic nerves - cause changes in heart rate or blood pressure
Unlike in the CNS, axon regeneration can occur in damaged peripheral nerves

42
Q

Describe the different diagnostic techniques for neuropathies

A

EMG - records muscle electrical activity, either intramuscular or surface. Used to distinguish between muscle and nerve disorders

Nerve conduction velocity - electrodes simulate nerves to determine conduction speed. Slow = damage. Infants will have low NCV

somatosensory evoked potential - electrodes stimulate sensory nerves to determine transmission to mechanoreceptors. Used in MS.

Neurology (12 decks)

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