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Neuroscience and mental health > PNS > Flashcards

PNS Flashcards

1
Q

what does the PNS include

A

everything except for the brain and spinal cord ie spinal and cranial nerves

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2
Q

what is the role of the PNS

A

it is the communication centre between the CNS and the body

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3
Q

2 main branches of the PNS

A

sensory and motor

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4
Q

2 branches of motor

A

autonomic and somatic

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5
Q

what does the somatic nervous system do

A

controls voluntary movement

skeletal muscle

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6
Q

what does the autonomic nervous system do

A

control involuntary responses

eg Bp and heart rate

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7
Q

branches to the autonomic nervous system

A

sympathetic and parasympathetic

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8
Q

describe the sympathetic nervous system

A

mobilises body systems

flight/fight responses

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9
Q

describe the parasympathetic action

A

conserves energy

rest and digest responses

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10
Q

what do sensory neurons do

A

carry information from sensory receptors in the skin and the viscera to the brain

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11
Q

which section is the cranial section

A

the head portion

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12
Q

what does the non-neuronal ectoderm give rise to in the development of neural crest cells

A

the skin

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13
Q

what does the neuronal ectoderm give rise to in the development of neural crest cells

A

cns

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14
Q

what does the neuronal fold give rise to in the development of neural crest cells

A

neuronal crest cells
they migrate - many lineages
between the skin and cns - relay information between them

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15
Q

what forms from neuronal crest cells

A

sensory neurons

and shwann cells

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16
Q

describe the structure of the sensory neuron

A

pseudounipolar
peripheral process - signal from skin/viscera to soma
central process to spinal cord

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17
Q

summarsie the structures of fibres A to C

A

a - myelinated somatic
b - myelinated visceral
c - unmyelinated somatic and visceral pain afferents

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18
Q

describe the structure of a fibres

A

free nerve endings
pseudounipolar
for pain

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19
Q

describe the structure of b fibres

A

encapsulated nerve endings
connective tissue capsule
pseudounipolar
pressure Pacinian corpuscle

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20
Q

describe the structure of c fibres

A

dipolar?

hearing hair cells in ear

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21
Q

describe the structure of d fibres

A

smell

cell body not in the ganglion

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22
Q

what does the motor division do

A

efferent

composed of motor neurons carry signal from CNS to effectors

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23
Q

describe the SNS

A

made of efferent nerves, important for muscle contraction
nerve signals begin in motor cortex
can be voluntary or automatic
nerves terminate at the NMJ to give a response
upper motor neurons in primary cortex are part of the CNS
lower motor neurons part of the PNS, cause response eg in reflex
neurons synapse with the brain stem and the spinal cord. lower motor neuron continue to skeletal muscle

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24
Q

development of the motor neurons

A

in lower part of the basal plate the lower motor neurons generate from the spinal cord itself

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25
Q

what is a motor unit

A

1 motor neuron innovates a range of muscle fibres

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26
Q

describe the peripheral processes of the sensory neurons

A

dorsal root

cell bodies in the dorsal root ganglion

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27
Q

describe the peripheral processes of the motor neurons

A

leave the spinal cord via the ventral root

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28
Q

where do the motor and sensory nerves go after their respective roots

A

mixed in the spinal nerve
the spinal nerve leaves through the invertebral foreman
spinal cord divide into posterior rami - ignal to skin on back, and ventral rami - feed front of body
paravertebral sympathetic chain ganglion goes into 2 rami

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29
Q

how many nerves are in the PNS

A

43 pairs

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30
Q

groups of spinal nerves

A 
cervical plexus 
brachial plexus
cervical enlargement 
intercostal nerves 
lumbar enlargement 
lumbar plexus 
sacral plexus 
cauda equina
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31
Q

describe the autonomic nervous system

A

efferent nerves and ganglia stimulating effectors out of our control
made of sympathetic and parasympathetic
composed of 3 neurons

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32
Q

describe the 3 neurons that make up the ANS

A

from hypothalamic nucleus (visceral motor nuclei) to brain stem nuclei/spinal cord
preganglionic neuron from spinal cord/brain stem to autonomic ganglia (pre synaptic if from vagal nerve/sacral parasympathetic nerves)
postganglionic from autonomic ganglia to visceral effectors (post synaptic if from vagal nerve/sacral parasympathetic nerves)

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33
Q

which nerves in the ANS are myelinated

A

preganglionic

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34
Q

describe the divisions of the ANS

A

nerves from T1 - L2 go to sympathetic chain

from here nerves go to the collateral ganglion or straight to organs

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35
Q

where do preganglionic or presynaptic neurons arise from

A

basal plate in spinal cord

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36
Q

difference between dorsal root ganglia and autonomic ganglion

A

dorsal exclusively contains cell bodies

autonomic ganglia has cell bodies and dendrites associated with synapses

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37
Q

how is the myelin sheath formed

A

from shwann cells that wrap around axon clockwise

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38
Q

features of the myelin sheath

A

major dense line (period line) - where the cytoplasm is condensed
minor dense line (intraperiod line) - plasma membrane
node of Ranvier allows saltatory conduction to take place

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39
Q

describe the myelination of C fibres

A

wrapped by 1 layer of the shwann cell and cytoplasm - neurilemma
many fibres are wrapped by the membrane of 1 neuron

40
Q

describe A fibres

A

largest fibres 5-20microns - less resistance
myelinated
somatic - sensory and motor to skeletal muscle
fast transmission
130m/s

41
Q

what is the propagation speed of a nerve impulse controlled by

A

size - larger = less resistance = faster
myelination - myelinated = saltatory conduction = faster
temperature

42
Q

describe B fibres

A

medium size - 2-3microns
15m/s
myelinated
visceral - sensory and autonomic preganglionic

43
Q

describe C fibres

A 
smallest 0.5 - 1.5microns 
2m/s 
unmyelinated 
sensory and autonomic motor 
pain
44
Q

explain how rootlets, roots, rami and ganglia link

A

rootlets form dorsal and ventral roots which go into rami

45
Q

how many cranial ganglia are there

A

4

46
Q

name the 4 cranial ganglia

A

ciliary ganglion
otic ganglion
pterygopalatine ganglion
submandibular ganglion

47
Q

describe the 3 sympathetic paravertebral and collateral pathways

A

preganglionic neuron goes through the ventral ramus
then either:
- through white ramus, synapse, postganglionic exits through the grey ramus to the spinal cord
- preganglionic move up/down the sympathetic trunk and synapse in the sympathetic ganglion
- pass through white ramus to splanchnic nerve and synapse later in the collateral ganglion

48
Q

where does the collateral ganglion lead to

A

the liver, spleen, adrenal glands, stomach, intestines, kidneys, urinary bladder, reproductive organs

49
Q

where do the nerves from the grey ramus go

A

sweat glands, piloerector muscles, bv of skin and skeletal muscles

50
Q

where do nerves from the sympathetic ganglion go

A 
iris
salivary glands 
lungs 
heart
thoracic
oesophagus
51
Q

what are nerve plexuses

A

networks of successive ventral rami that exchange fibres (crisscross and redistribute)
mainly innervate the limbs
lumbosacral and brachial plexus innervate the skin
thoracic ventral rami don’t form nerve plexuses

52
Q

what innovates dermatomes

A

dorsal root of the spinal nerves

53
Q

describe dermatomes

A

skin is continuous - can have overlap
area of skin supplied by single spinal nerve root
stacked along the thorax and abdomen
longitudinally along the limbs

54
Q

clinical significance of dermatomes

A

can use pin prick test to determine the site of spinal damage

55
Q

describe visceral afferents

A

not part of autonomic ns
nerve fibres from the organ - use sympathetic nervous system
pass through splanchnic nerves and plexuses, sympathetic collateral, and paravertebral ganglia and white rami to get to spinal dorsal root

56
Q

describe the cutaneous distribution of peripheral nerves

A

area of skin supplied by a nerve that comes off a plexus (eg brachial and lumbosacral plexus to upper and lower limbs)
sensory neurons of the peripheral nerve may come from >1 spinal root eg lateral antebrachial cutaneous - C5-7

57
Q

clinical significance of cutaneous distribution of peripheral nerves

A

identify which individual peripheral nerve is damaged by pin prick exam

58
Q

describe myotomes

A

muscles that are supplied by single motor neuron root
ventral root
some muscles are supplied by >1 root
all muscle is supplied by the root of that nerve

59
Q

describe peripheral neuropathies

A

damage/disease affecting PNS nerves
may impair sensation, movement gland or organ function
sensory nerves - tingling, pain and numbness
motor nerves - weakness to hands and feet
autonomic nerves - changes in heart rate or bp

60
Q

describe monopathy

A

single nerve being affected

diabetic - ocular motor nerve - eye

61
Q

describe polyneuropathy

A

several nerves are affected

gillian barre - inflammatory

62
Q

causes of peripheral neuropathies

A

metabolic, toxic, inflammatory, traumatic, genetic, idiopathic

63
Q

structure of nerve

A

Connective tissues:
endoneurium - around each individual neuron, loose collagen fibrils
perineurium - around a fascicle (bundles of neurons and axons) - give tensile strength made of collagen
[between fascicles - have bv]
epineurium - around the entire nerve, dense, collagenous, have a blood supply, some fatty tissue

64
Q

where is the PNS nerve structure present

A

on everything beyond the spinal cord

65
Q

describe neuropraxia

A 
small compression 
axon can be repaired 
reversible conduction block 
selective demyelination of axon sheath 
endoneurium and axon still in tact
66
Q

describe axonotmesis

A

demyelination and axon loss
epineurium and perineurium remain in tact
still some continuity with the nerve
degeneration below and proximal to the site of injury

67
Q

describe neurotmesis

A

more sever injury - less likely for complete recovery
scaffold disrupted
associated with complete nerve division and disruption
seen after toxic/ischemic injuries
damage to endoneurium, perineurium and epineurium, around centre of nerve - no nerve growth (different degrees eg endo, endo and peri, endo and peri and epi)

68
Q

describe axon regeneration

A

distal portion of axon is phagocytosed - remove myelin and axon - Wallerian degeneration
proximal end of nerve fibre regenerating into tube of shwann cells - stump from axon grow, try to reach tissues
shwann cell proliferate

69
Q

what happens in a neuroma

A

axon doesn’t find final position

makes nerves there

70
Q

what does avulsed mean

A

not in tact

71
Q

what happens if there is avulsion in the ventral root and dorsal root

A

ventral: degeneration - it is not attached to the cell body

in dorsal cell body is attached so still intact

72
Q

how do you do an EMG

A

put needle in muscle

73
Q

what is the purpose of an EMG

A

distinguishes between myopathies and muscle weakness due to nerve pathology

74
Q

what creates a larger response on the EMG

A

the fibre being closer to the electrode

75
Q

ehat is myopathy

A

damage to the muscle fibre

76
Q

what is the effect of myopathy on contractions

A

they are spontaneous
less frequent than in the nerves
signal is smaller

77
Q

what is a nerve conduction study

A

a diagnostic technique for evaluating the speed of nerve impulses

78
Q

Describe the NCS

A 
involves the median nerve (in arm) 
electrodes are placed on the nerve 
create an electric field 
this stimulates the nerve 
the EMG is recorded at the surface
79
Q

calculation for the conduction velocity

A

distance cm/(proximal latency - distal latency ms)

80
Q

difference in latency between proximal and distal electrodes

A

proximal has a larger latency time

81
Q

what can you measure in a NCS

A

NCV in m/s

amplitude of responses in mV

82
Q

conditions you can see with a NCS

A

anoxopathies (from amplitude) and demyelinating neuropathies (from NCV)

83
Q

what are axonal neuropathies

A

damage to the axons

84
Q

result of axonal neuropathy

A

reduced amplitude

85
Q

result of demyelination in NCS

A

proximal is delayed

86
Q

result of demyelination and a conduction blocker in NCS

A

lower amplification
more delayed
Gillian Barre syndrome

87
Q

what is a somatosensory evoked potential

A

evaluation of the site of a lesion in somatosensory pathways by assessment of amplitude and latency

88
Q

why do you need to average many responses

A

the amplitude from the nerve responses is very small

so need averaging of 100 samples to get rid of noise

89
Q

where do you put the electrodes in SEP

A 
lower neck 
back of the neck
cortex
thalamus
spinal area
90
Q

how can you tell there is a lesion in SEP

A

there is a delay

91
Q

alternative method to SEP to confirm a lesion

A

take a biopsy

92
Q

which nerves don’t have ganglia

A

sacral and vagus

93
Q

what type of nerve fibres are preganglionic and presynaptic

A

myelinated b fibres

multipolar

94
Q

where do the postganglionic and synaptic fibres arise from

A

the crest cells

95
Q

describe the postganglionic and synaptic fibres

A

multipolar

unmyelinated c fibres

96
Q

what is the effect of a denervated muscle on an EMG

A

damaged nerve
surrounding nerves take over
larger signal there
fibrillation

Neuroscience and mental health (14 decks)

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