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Neuroscience and Mental health > 10. Peripheral nervous system > Flashcards

10. Peripheral nervous system Flashcards

1
Q

What does the neural component of the ectoderm give rise to?

A

CNS

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2
Q

Where are neural crest cells located and what is their function?

A

Located in neural fold (At the junction between non-neural and neural ectoderm)
Function: Relay info. between skin and CNS

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3
Q

What does the non-neural component of then ectoderm give rise to?

A

Skin

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4
Q

List 3 types neurone fibres

A

A fibres: Myelinated Somatic (associated with skeletal muscles)
B fibres: Myelinated Visceral (associated with internal organs)
C fibres: Unmyelinated Somatic and Visceral pain afferents

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5
Q

What does the autonomic nervous system control?

A

Involuntary responses

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6
Q

Describe the arrangement of autonomic motor neurons.

A

Autonomic motor neurons have a preganglionic neuron and a postganglionic neuron with an autonomic ganglion in the middle.
Location of the autonomic ganglion varies depending on whether it is sympathetic (spinal cord) or parasympathetic (brain stem nuclei or sacral region)

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7
Q

Where do sensory neurons have their cell bodies?

A

In the dorsal root ganglion

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8
Q

Which vertebrae do sympathetic nerves arise from?

A

T1 to L2

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9
Q

Why do we refer to vagal and sacral nerves as presynaptic or postsynaptic?

A

There are no ganglia associated with vagal or sacral nerves

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10
Q

Where do pre-synaptic parasympathetic sacral neurones arise from?

A

S2 to S4

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11
Q

Describe common developmental features of Pre-ganglionic sympathetic motor neurones (T1 – L2)
and Pre-synaptic parasympathetic Sacral neurons (S2-4).

A

Arise from basal plate of spinal cord
Multipolar
Myelinated
B fibres

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12
Q

Describe common developmental features of Post-ganglionic autonomic (symp. and parasymp.) neurones
and post-synaptic parasympathetic neurons

A

Arise from neural crest cells
Multipolar
Unmyelinated
C fibres

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13
Q

How do autonomic motor ganglia differ to ganglia of sensory neurones?

A

Autonomic motor ganglia contain synapses

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14
Q

Describe the difference in myelination of A and C fibres

A

A fibre: 1 axon, many layers of myelin

C fibres: Many axons associated with 1 Schwaan cell

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15
Q

What do rootlets come together to form?

A

Roots

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16
Q

Describe parasympathetic ganglia

A

Located in CRANIAL part of head

Synapases between pre-ganglionic and post-ganglionic fibres

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17
Q

What are the 4 parasympathetic ganglia?

A

Ciliary
Submandibular
Otic
Pterygopalatine

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18
Q

What are the 2 divisions of the peripheral nervous system?

A

Autonomic: Motor, sensory and enteric
Somatic: Motor and sensory

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19
Q

How many and what types of nerves are in the peripheral nervous system?

A

43 pairs:
12 Cranial
31 Spinal

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20
Q

Describe the distribution of spinal nerves in the peripheral nervous system

A 
8 cervical 
12 thoracic
5 lumbar
5 sacral
1 coccygeal
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21
Q

Where do all except C1-C7 of the spinal peripheral nerves arise from?

A

Arise from below corresponding vertebra

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22
Q

Generally, peripheral nerves have… function

A

Have mixed motor and sensory function

aside from some cranial nerves

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23
Q

Describe transmission in somatic motor nerves

A

Primary motor cortex to brainstem/spinal cord to NMJ (skeletal muscle)
Always stimulatory, don’t fire at rest
Use ACh

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24
Q

Describe transmission in autonomic motor nerves

A

Hypothalamus to brainstem/spinal cord to ganglion to effector organ
Stimulatory or inhibitory, baseline firing rate
ACh or NA

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25
Q

Describe transmission in somatic and autonomic sensory nerves

A

Periphery to dorsal root ganglion to brainstem/spinal cord

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26
Q

What does somatic and autonomic sensory innervation give?

A

Sensory info from conscious (somatic) and visceral (autonomic) areas

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27
Q

What is found in the ventral root?

A

Somatic and autonomic motor neurones

Efferent nerves

28
Q

What is found in the dorsal root?

A

Somatic and autonomic sensory neurones
Afferent nerves
Cell bodies in dorsal root ganglion (collection of cell bodies)

29
Q

What is found in a spinal nerve?

A

Motor and sensory neurones of that spinal segment

30
Q

What is found in a dorsal ramus?

A

Motor and sensory innervating the skin of the back and deep back muscles

31
Q

What is found in a ventral ramus?

A

Motor and sensory innervating the rest of the body from the neck down

32
Q

What is found in the ventral horn of grey matter?

A

Somatic motor neurones

Efferent nerves

33
Q

What is found in the dorsal horn of grey matter?

A

Somatic and autonomic sensory neurones

34
Q

What do all sensory neurones of the PNS arise from?

A

Neural crest cells

35
Q

Which roots do motor and sensory nerves go out of?

A 
Motor = ventral
Sensory = dorsal
36
Q

Describe peripheral nerve structure

A

Nerve surrounded by epineurium
Bundle of neurones (fascicle) surrounded by perineurium
Neurone/axon surrounded by endoneurium

37
Q

What produces myelin in the peripheral nervous system?

A

Schwann cells

38
Q

What affects propagation speed of a nerve impulse?

A

Size: Larger fibres conduct impulses faster as less resistance
Myelination: Myelinated = faster due to saltatory conduction
Temperature: Increased temperature = faster

39
Q

Describe A fibres

A 
Largest (5-20 microns)
Fastest conduction (130 m/s)
Myelinated Somatic
Sensory and motor to skeletal muscle
Sub-divided into alpha, beta, delta and gamma
40
Q

Describe B fibres

A

Medium (2-3 microns)
Medium conduction (15 m/s)
Myelinated Visceral
Sensory and autonomic preganglionic

41
Q

Describe C fibres

A

Smallest (0.5-1.5 microns)
Slowest conduction (2 m/s)
Unmyelinated somatic and visceral pain afferents

42
Q

Nerve plexus

A

Network of successive ventral rami that exchange fibres (e.g cervical, brachial plexus)

43
Q

Dermatomes

A

Area of skin supplied by a single sensory nerve root (can determine site of spinal damage)

44
Q

Myotomes

A

Groups of muscles supplied by a single spinal nerve root (part of neurological exam)

45
Q

Ramus

A

Motor and sensory nerves together that exit from the roots

46
Q

What are the 2 classifications of distributions of sensory innervation?

A

Dermatomal Innervation: The strip of skin supplied by a pair of spinal nerves is referred to as a dermatome
Peripheral Innervation: The area of skin supplied by a single peripheral nerve

47
Q

What does the brachial plexus innervate? Which ventral rami does it consist of?

A

Brachial plexus innervates the upper limb.

Consists of ventral rami of C5-T1

48
Q

What does the lumbosacral plexus innervate? Which ventral rami does it consist of?

A

Lumbosacral plexus innervates lower limbs.

Consists of ventral rami of L1-S3

49
Q

Causes of neuropathies

A

Many causes e.g. metabolic, inflammatory, genetic

30% idiopathic

50
Q

Mononeuropathy

A

Single nerve affected

51
Q

Polyneuropathy

A

Several nerves affected

52
Q

What does damage to a sensory nerve cause?

A

Tingling
Pain
Numbness

53
Q

What does damage to a motor nerve cause?

A

Weakness to hands and feet

54
Q

What does damage to autonomic nerves cause?

A

Change in HR

Change in BP

55
Q

How do damaged peripheral nerves differ to those in the CNS?

A

Axon regeneration can occur in damaged peripheral nerves

56
Q

Describe neuropraxia

A 
Compression in axon
Reversible conduction block
Selective demyelination 
Axon, Epi-,Peri- and Endoneurium still intact
e.g. nerve compression
57
Q

Describe Axontomesis

A 
Disruption of axon and degeneration of fibre
Demyelination. 
Axon loss. 
Nerve regrowth possible. 
Epi- and Perineurium intact
58
Q

Describe Neurotmesis

A 
Complete nerve division and disruption
Disruption to epi-, peri- and endoneurium
Damage to epineurium- no nerve growth
Axon loss. 
Common after toxic or ischaemic injury
59
Q

Rank peripheral neuropathies from mild to severe

A

Neuropraxia
Axontomesis
Neurotmesis

60
Q

List 3 diagnostic techniques for peripheral neuropathies

A

Electromyography (EMG)
Nerve conduction velocity (NCV)
Somatosensory evoked potential (SEP)

61
Q

Describe an EMG

A

Records electrical activity produced by muscles
Intramuscular or surface EMG
Distinguish muscle disorders vs nerve disorders

62
Q

Describe an NCV

A

Electrodes stimulate nerves to determine conduction speed
Slow speed indicates nerve damage
E.g trauma, diabetic/peripheral neuropathy, viral infection, nerve entrapment
(Infants <3yrs have low NCV)

63
Q

Describe a somatosensory evoked potential

A

Electrodes stimulate sensory neurones to determine transmission of sensory info from mechanoreceptors to CNS
Often used in multiple sclerosis

64
Q

What is the basal plate?

A

Basal plate develops into the ventral horn

It is where the motor neurones come from

65
Q

What is the Alar plate?

A

Alar plate develops into the dorsal horn

It is where the sensory neurones go to

66
Q

2 types of sympathetic ganglia

A

Paravertebral

Collateral

Neuroscience and Mental health (11 decks)

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