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Flashcards in 473 MT 2 Deck (122):
1

sensory modalities in the order of decreasing axon size

proprioception, superficial touch, deep touch, vibration, pain, temp, itch

2

dermatome

sensory area/cutaneous region innervated by a single spinal segment

3

C5 innervates what dermatome
C6, C7, C8
T4
T10
L2
L3
L4
L5

shoulder
hand
nipple level
belly button
thigh
knee
medial leg
lateral leg

4

what sensory info does PMCL carry?

vibration, proprioception, tight touch

5

what does antero-lateral pathway carry?

pain, temp, crude touch

6

primary sensory neuron in PMCL

-cell body in DRG
-bifurcates: axon 1. projects to receptor and 2. enters dorsal horn and splits again-->some to alpha motor neurons in anterior horn, others to posterior column to ascend

7

where do primary sensory neurons for the lower body travel?

fasciculus gracilis
medial portion of posterior column
(leg=medial)

8

where do primary neurons for the upper body travel?

fasciculus cuneatus
lateral posterior column
(arms=lateral)

9

why would the axons for the legs be more medial?

first to enter
avoids crossing of wires

10

where do axons in fasciculus gracilis synapse?
axons in fasciculus cuneatus?

nucleus gracilis
nucleus cuneatus

11

2nd order sensory neuron in PMCL

nucleus gracilis: cell bodies of afferent for medial part
nucleus cuneatus-cell bodies of afferents for lateral part (more lateral)
-axons cross at caudal medulla, then project to thalamus as medial lemniscus pathway

12

3rd order sensory neuron for PMCL

cell body in thalamus, projects to primary sensory cortex

13

antero-lateral pathway consists of

spino-thalamic
spino-reticular
spino-mesencephalic

14

what does mesencephalic refer to?

midbrain region

15

primary sensory neuron of AL pathway

cell body in DRG, synapse w/ 2nd order in dorsal horn of spinal chord
-in 2nd order sensory nuclei

16

2nd order sensory neuron AL pathway

crosses midline through anterior comisure over 2-3 segments
ascends in anterolateral white matter
synapse in thalamus

17

3rd order neuron AL pathway

thalamus to somatosensory cortex

**only spino-thalamic projects to cortex

18

thalamus functions

relay centre for integration of sensory, cerebellar, and basal ganglia inputs and cortical inputs
-there's a collection of relay nuclei
-ie 1st order of higher level sensory processing

19

somatosensory cortex somatotopic organization

mirror image of motor cortex
larger areas for hand, mouth, tongue

20

negative symptoms of somatosensory lesions

PMCL pathway
-loss of position and vibration sense
-loss of discriminatory touch (2pt touch)
-astereognosis (can't recognizing objects)
-sensory ataxia-unsteadiness, poor coordination, worse w/out vision

21

how to test for loss of position sense

move joints passively and ask if it was up or down (eyes closed)

22

how to test for vibration sense

tuning fork

23

how to test for two-point discrimination

ask if being touched in 1 or 2 places
or light touch in one direction and ask which direction

24

tabetic gait

from total loss of proprioception in the legs
-high stepping to get limb through swing phase
-foot flaps (no position sense)
-more locked knees b/c it's clearer where it is

25

what distinct difference does tabetic gate have from foot drop?

in foot drop, toes hit first b/c of weak dorsiflexors

26

what happens from damage to primary sensory neuron (PMCL)?

loss of proprioception + tabetic gate possible
loss of deep tendon reflexes
-PMCL neurons involved in monosynaptic stretch reflex pathways

27

neg. symptoms (spino-thalamic pathway)

loss of pain and temp
reduced touch sensation

28

how to test for pain and temp

pain: pin prick and see if there's a sharp feeling
temp: hot and cold vials
crude touch is difficult to test if PCML is still intact

29

positive PCML symptoms

tingling, numb sensation
-parathesia and dysesthesia, meaning abnormal sensations

30

positive antero-lateral symptoms

sharp, burning or searing pain
may by hyperpathia-excessive pain to something normally painful
or allodynia-pain to something normally not painful

31

positive primary sensory neuron symptoms

radicular pain
numbness and tingling in dermatome

32

trigeminal nerve

-CNV
-3 branches-1, 2, and 3
-includes motor element (chewing)
-cell bodies in trigeminal ganglion in Merkel's cave
-axons project to pons

33

2nd order sensory neuron (inputs from face)

synapses on ipsi-lateral side at the level of the pons
-crosses midline and continue to thalamus
-3rd order from thalamus to somatosensory cortex

34

where to pain, temp, and crude touch axons go (facial inputs)?

they project through the ganglion into the pons, then descend into long spinal-trigemenal nucleus, which is continuous w/ the spinal chord and extends to the pons

35

loss of sensation on whole side of face?

trigemenal nerve, ipsilateral side
if cortex was damaged, contralateral side would be affected

36

loss of sensation on right side of face and body?

-pons or above (if IN, sensory loss would be on contralateral side of body)
-likely in the lateral thalamus on the contralateral side

37

loss of sensation on one side of the body?

-likely medial lemniscus pathway, might involve anterolateral
-more ventral would involve pyramids

38

loss of sensation in face on one side and body on the other?

@ the level of the pons
where anterolateral pathways travel together
but body afferents have crossed midline already

39

single dermatome sensation loss?

damage to nerve itself
or dorsal root
**nerve would also involve radicular pain and motor involvement

40

Brown-Sequard syndrome definition + causes

-hemicord lesion

penetrating trauma
compression from a tumour
MS

41

hemicord lesion symptoms

lower MN symptoms on ipsilateral side for muscles innervated by that spinal chord level
upper MN on ipsilateral side for muscles innervated by axons below that level
-loss of proprioception, light touch, and vibration for dermatomes innervated by that level and below on the ipsilateral side
-loss of pain, temp, and crude touch for dermatomes innervated by the segment injured and 1 segment below on the ipsilateral side
-loss of pain, temp, crude touch for dermatomes innervated by 2 segments below and lower on the contralateral side

42

transverse chord lesion causes

trauma, tumor, MS

43

transverse chord lesion symptoms

bilateral lower MN symptoms at that level
bilateral upper MN symptoms below
bilateral PCML loss at that level and below
bilateral anterolateral loss at this level and below

44

central chord syndrome (small lesion)

-starts as a syrinx, then gets inflammed and grows
-small enough not to affect motor pathways
-affects 2nd order neurons crossing in spinal chord in anterolateral pathways
-bilateral loss of sensory info for dermatomes innervated by 1-2 segments below
-anterior horn being unaffected spares levels below

45

posterior chord syndrome causes

-trauma
-tumor
-MS
-vit B12 deficiency (can damage myelin of posterior column axons)
-tabes dorsalis

46

anterior chord syndrome causes

trauma
tumor
MS
infart
-causes anterolateral sensation and motor loss below the neck
-if affecting lateral corticospinal tract, upper MN symptoms in levels below

47

where can herpes zoster lie dormant?
what is happening when it re-emerges?

DRGs
grows down sensory nerve
-pain, rash in dermatome
-allodynia and parasthesias also
-subsides after 2-3 weeks

48

what is the name for shingles cases lasting for months?

post-hepatic neuralgia

49

tabes dorsalis

-slow degeneration of dorsal columns, dorsal roots, and ganglia of the spinal chord
-lumbar region
=late symptoms of untreated syphilis (10-30 yrs later)

50

tabes dorsalis symptoms

proprioceptive loss, parasthesias, allodynia
tabetic gate
bad balance w/ out vision

51

mononeuropathy

nerve disorder of one nerve
eg carpal tunnel
-may have sensory symptoms and motor deficits

52

polyneuropathy examples

-diabetes
-overdoes of vit B6
-ganglionopathies
-polyneuritis

53

diabetic neuropathy causes

poor blood supply + inflammation of nerves
-from high levels of glucose
-involves paresthesias and allodynia

54

what does polyneuropathy in the hands and feet immediately rule out?

-lesion in the brain
-lesion in the spinal chord

55

overdose of pyridoxine

damages large 1a myelinated fibers, some cases irreversible
-up to 100x normal does leads to sensory loss

56

ganglionopathies

typically autoimmune
leads to polyneuropathy

57

polyneuritis

inflammation of many nerves leading to widespread proprioceptive or sensory loss
-eg GL-loss of sensory input below nose (anterolateral largely spared)

58

where is the vestibular system located?

w/in petrous ridge of temporal bone
continuous w/cochlea

59

what is the bony labarynth

tunnels carved through petrous ridge
-filled with endolymph fluid

60

which otolith organ is closer to the cochlea?

saccule

61

how many semi-circular canals?

anterior
posterior
inferior

62

which otolith organ is continuous with the semi-circular ducts?

utricle (through ampulla)

63

where do hair cells lie in the semi-circular ducts

crista ampullaris
axons project to vestibular ganglion

64

cupola

gelatinous material encasing the cilia
-endolymph pushes against gel-encased hair cell

65

what do hair cells in the ampulla detect?

angular accelreation of the head
-fluid lags in the ducts and deflects the cupula and cilia

66

where are the utricles located?
why is that important?

toward midline
for orientation in horizontal movement of the head-when deflected toward utricle (midline), that side depolarizes and other side hyperpolarizes

67

what does rightward movement of the head do to firing rates?

L side inc
R side decrease

68

anterior and posterior canal firing rates

increase if hair cells are deflected AWAY
decrease if hair cells deflected toward

69

where are hair cells in the otolith organs?

in macula, with cilia embeded in the otolithic membrane

70

otoconia

Ca carbonate crystals on top the otolithic membrane
-adds density-->inertia

71

how are hair cells in utricle oriented?

vertically (from floor)
-ie good for detecting forward/backward/side to side motion

72

how are saccule hair cells oriented?

horizontally from wall
-ie good for detecting vertical and some backward forward motion

73

otolith firing rates

utricle: increase rate when hair cells are deflected toward striola
saccule: decrease (hair cells face out)

74

which motions have similar vestibular signals?

backward tilt and acceleration b/c hair cells fire normally at constant velocities

75

where are cell bodies of vestibular afferents?
axons?

vestibular ganglion
axons travel as CN VIII to ipsilateral vestibular nuclei

76

lateral vestibulospinal tract

control balance and extensor tone in limbs

77

medial vestibulospinal tract (medial and inferior nuclei)

positioning of head and neck
vestibulo-colic reflexes

78

how are eye muscle reflexes present?

SVN and MVN projections via medial longitudinal fasciculus to 3 cranial nuclei
1. oculo-motor nucleus
2. trochlear nucleus
3. abducens nucleus

79

how does vestibular system influence balance

-reciprocal projections with the cerebellum
-balance, eye control, coordination
-cerebellum maintains some control over eye movements for control

80

how is head orientation and motion consciously perceived?

projections from vestibular nuclei to thalamus to parietal cortex

81

VOR

allows eyes to fix on a target while head is accelerating
-eyes move in opposite direction of head with the same acceleration (same direction as cupula movement)

82

describe firing w/L movement of head for VOR

L movement causes R endolymph movement
L side increase output to vestibular nuclei
excitation of R side eye muscles pulls eyes to the R
-opposite side muscles inhibited

83

nystagmus

=from continual vestibular stimuli
-eyes snap back to center so VOR can continue when spinning
-named after fast phase (a right VOR response might cause L beating nystagmus)

84

head impulse test

move head passively and quickly while subject wears goggles equiped w/accelerometers
tests canals in all planes
would expect to see equal and opposite eye movements

85

caloric irrigation testing

hot/cold water injection to ear
-cool water causes opposite side nystagmus (endolymph sinks)
-hot water causes same side nystagmus (endolymph rises)
COWS (cold opposite warm same)

86

what test is specific to otolith function?

vestibular evoked myogenic potentials
-sounds of tones or clicks used to stimulate otoliths primarily
-mm activity recorded around neck and head
-sound causes stapes to push into vestibular system that cause stimulation
-largest response is on ipsilateral side
-muscles must be tonically active (ie person is looking up or holding head up)

87

peripheral vestibular lesion

damage to labyrinths or CN VIII

88

central vestibular lesions

damage to vestibular nuclei or pathways projecting to brainstem, thalamus, or cerebellum

89

common symptoms of uni-lateral vestibular lesion

vertigo
nausea
postural instability

90

what causes vertigo?

spontaneous nystagmus
eg if the nerve was damaged, firing rate would be imbalanced
this is interpreted an unexpected head movement

91

cause of nausea as a vestibular lesion symptom

a. sensory mismatch/conflict with visual world
b. vestibular-autonomic connections
-these exist to transmit info about head movement in order to adjust BP but can also cause autonomic response of nausea)

92

postural instibility in vestibular patients

fall or turn (fakuda marching test) toward side of lesion

93

what role does research suggest the vestibular system plays in balance responses?

regulating amount and coordination
NOT for initiating the response (slower responses than reflexes)

94

6 possible causes of uni-lateral vestibular lesions

tumor
vestibular neuritis (CN VIII)
surgery
Meniere's disease
perilymph fistula
benign paroxysmal peripheral nystagmus

95

cerebellar pontine angle tumor

can impinge on CN VIII coming from pons level and possibly some vestibular nuclei

96

vestibular neuritis cause

viral infection of vestibular nerve
40% recover after a month, some have partial deficits

97

surgery

damaging one side to allow for compensation is sometimes a better route
-labyrinthectomy (plug canals or damage hair cells)
-vestibular nerve section

98

Meniere's disease

mechanism
-increased endolymph volume and pressure
-small ruptures of membranous labyrinth
cause
-unknown/maybe viral or autoimmune or genetic
treatment: lifestyle change, surgery

99

perilymph fistula

round/oval window rupture, which separates middle ear
-traumatic injury or severe pressure damage (eg scuba diving)
-treated w/rest or surgery

100

signs of perilymph fistula

abnormal nystagmus with additional pressure changes (in fistula test)

101

benign paroxysmal peripheral nystagmus

due to otoconia getting dislodged and traveling in canals
-symptoms w/sudden head changes
-they usually dissolve w/in a few weeks

102

how is BPPN identified?

dix hallpike-turn head in certain directions

103

what causes BPPN?

age
or massive head acceleration (eg a fall)

104

bilateral vestibular loss symptoms

postural instability (especially w/out vision)
blurry vision (when moving and trying to fixate)
missing postural responses

105

possible causes of bilateral vestibular loss

ototoxic medicaiton (ie gentomicin)
meningitis itself
meniere's disease can be bilateral

106

what does abnormal VOR and normal optokinetic reflex suggest?

damage at the canal (intact visual system)

107

what would happen to the VOR and optokinetic reflexes if medial vestibular nuclei were damaged?
what type of vestibular lesion is this?

both affected
-optokinetic bypasses receptors but goes to medial vestibular nucleus and then follows VOR path to adjusts eyes to reduce retinal slip
**central lesion

108

unimodal association cortex

higher level processing of 1 function

109

multimodal association cortex

integration of several sensory modalities for higher level processing

110

motor association cortex

involved in formulating motor programs
-supplimental motor area superior and medial
-pre-motor cortex lateral

111

motor association area projections

-primary motor cortex
-brainstem
-spinal chord (corticospinal tract fibers)

112

what does stimulation of the pre-motor cortex cause?

multiple contractions at multiple joints of the same limb

113

what is the pre-motor cortex involved in?

preparation of voluntary movements and activating multiple muscles in the limb
-set related movements and directionally specific (affects contralateral limbs)

114

supplementary motor area

-complex sequences of movements
-bilateral coordination of limbs
-affects contralateral limbs
-influences proximal muscles directly
-influences distal muscles via primary motor cortex
-inter-hemispheric connections exist b/t the two sides

115

agnosia

normal percept stripped of all meaning
stereoagnosis-inability to recognize/name objects
agraphesthesia-inability to recognize symbols, numbers, etc. from light touch

116

somatosensory association cortex lesion

agnosia
basic elements of where and what but that information can't be integrated and given meaning to

117

visual agnosia

features can be identified but can't be integrated to give meaning and name too
-facial recognition intact (frontal cortex)
-motor function intact: sometimes the motion of a tool happens in their hands and then they can identify it
-also could name objects if they picked them up with eyes closed

118

parietal association cortex

integrates visual, somatosensory, vestibular, and auditory inputs
-primarily parietal but also frontal (ie multimodal)
-outputs include motor association areas

119

which hemisphere deals with skilled motor formulation?

dominant
also called praxis
ie Left
-particularly when interacting w/tools or the environment

120

dominant hemisphere functions

-language
-analytic skills
-musical sequencing and analytical skills

121

non-dominant hemisphere functions

musical ability
sense or direction-spatial orientation
visual-spatial analysis and spatial attention
prosody (emotion in tone of voice)

122

apraxia

damage to either motor association areas or L parietal association cortex
--inability to perform complex sequences of tasks