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Neuroanatomy > Motor and Sensory Pathways > Flashcards

Motor and Sensory Pathways Flashcards

1
Q

tracts of NS can be divided into…

A

ascending (sensory) and descending (motor) tracts

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2
Q

commissure

A

bundle of fibres crossing from one side of the body to the other at the same level (straight across) - e.g. corpus callosum is the largest commissure of the body also an anterior and posterior commissure, hippocampal commissure, etc.
- Good for communication between hemispheres

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3
Q

decussation

A

‘crossing over’ - fibres descending from the brain down the spinal cord and they cross over obliquely (form an x-shape)

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4
Q

are descending tracts sensory or motor?

A

motor

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5
Q

are ascending tracts sensory or motor?

A

sensory

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6
Q

UMN

A

nerves in CNS (brain and spinal cord)
- Stroke, tumour, etc. indicate damage

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7
Q

LMN

A

nerves in PNS (outside of brain)
- Includes cranial nerves as they are outside of the brain

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8
Q

descending pyramidal tracts we need to know

A

lateral and ventral corticospinal tracts
corticobulbar tract

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9
Q

what is a pyramidal tract?

A

axons cross over at the medullary pyramids

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10
Q

role corticospinal tract

A

carry conscious motor control from primary motor cortex down spinal cord via UMN

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11
Q

where does corticospinal tract decussate?

A

medullary pyramids

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12
Q

are pyramidal tracts conscious or unconscious

A

conscious

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13
Q

are extrapyramidal tracts conscious or unconscious

A

unconscious

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14
Q

route of corticospinal tract

A

conscious motor control from primary motor cortex

decussation in medullary pyramids

UMN passes into corticospinal tract in white matter of spinal cord and tract descends until level at which signal is due to leave spinal cord

UMN passes into grey matter and synapses with LMN, which exit the spinal cord to form peripheral nerves and travel to muscle

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15
Q

lateral corticospinal tract contains…

A

signals responsible for moving the muscles of the limbs

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16
Q

lateral corticospinal tract decussates where?

A

medullary pyramids

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17
Q

ventral corticospinal tract contains…

A

signals that will innervate the muscles of the trunk

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18
Q

ventral corticospinal tract decussates where?

A

not at the medullary pyramids - from the primary motor cortex signals enter the lateral corticospinal tract on same side and descend to the level they are due to leave at on the spinal cord where they decussate to the other side and leave immediately.

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19
Q

corticobulbar tract role

A

motor pathway connecting the primary motor cortex to the medulla

conscious motor innervation to muscles of face, head and neck region (not eyes)

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20
Q

corticobulbar tract contains…

A

UMN that will synapse with motor cranial nuclei of the cranial nerves

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21
Q

extrapyramidal motor tracts to know

A

rubrospinal
reticulospinal
vestibulospinal
tectospinal

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22
Q

rubrospinal tract

A

cervical area of spinal cord

fine-tuning movements of upper limbs

originates in the red nucleus of the midbrain

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23
Q

reticulospinal tract and vestibulospinal tract

A

posture, balance and coordinating movements

vestibulospinal tract is an uncrossed pathway

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24
Q

tectospinal tract

A

orientating eyes and head towards sounds as part of auditory and visual reflexive pathways

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25
where are LMN found?
peripheral nerves connecting signal from UMN to target muscle
26
part of spinal cord LMN leaves in motor route
ventral horn
27
part of spinal cord LMN enters in sensory route
dorsal horn
28
dorsal horn receives...
sensory info
29
ventral horn has...
motor neurons
30
lateral horn in what levels only...
thoracic
31
central canal of spinal cord contains...
CSF
32
what connects sides of spinal cord?
Ventral white commissure and the grey commissure
33
grooves between the hemispheres of the spinal cord
Dorsal median sulcus and ventral median fissure
34
Vertebral foreman
where the spinal cord runs through
35
role of UMN
motor innervation of LMN inhibitory effect on muscle stretch reflex
36
role of LMN
motor component in peripheral nerve
37
example of UMN lesion
stroke CNS tumour
38
example of LMN lesion
peripheral nerve laceration peripheral tumour
39
UMN lesion and fasciculations
absent
40
LMN lesion and fasciculations
present
41
UMN lesion and muscle wasting
present after some time due to lack of use (physiologic muscle atrophy)
42
LMN lesion and muscle wasting
present due to loss of neurotrophic factors at the LMN (neurogenic muscle atrophy) quicker onset
43
muscle tone and UMN lesion
hypertonia - loss of inhibitory pathways
44
muscle tone and LMN lesion
hypotonia
45
power and UMN lesion
reduced power
46
power and LMN lesion
reduced
47
reflexes and UMN lesion
hyperreflexia
48
LMN lesion and reflexes
hyporeflexia
49
UMN lesion and babinski sign
positive
50
LMN lesion and babinski sign
negative
51
UMN lesion and clonus
present
52
LMN lesion and clonus
absent
53
what is muscle tone
natural resting contraction of the muscles
54
what is atrophy
muscle wastage
55
what are fasciculations
muscles twitching
56
what is babinski sign?
type of reflex - UMN lesion: toes go up (dorsiflexion) (positive) - LMN lesion: toes go down (plantarflexion - normal) negative
57
what is clonus?
differences in the knee reflex test - UMN lesions: present - LMN lesions: absent
58
where can UMN lesions occur?
any part of descending motor tracts - pyramidal susceptible as span length of CNS and pass internal capsule
59
if lesion is found on left or right corticospinal tract before level of decussation at the medulla effects will be seen where?
contralaterally - opposite side
60
damage to corticobulbar tract results in...
mild muscle weakness due to bilateral nature of tract (except facial palsy)
61
why is there hypertonia in UMN lesions?
due to disinhibition of alpha and gamma neurons
62
Brown Sequard syndrome
- Hemisection of SC - Paralysis and loss of proprioception on the same side as the injury - But loss of pain and temp sensation on the opposite side as lesion
63
LMN describe...
damage to alpha motor neurons found in peripheral NS innervating skeletal muscles occur anywhere from the anterior horn to the peripheral nerves neuromuscular junction
64
what type of neurons are sensory neurons?
bipolar
65
where are sensory neurons nuclei found?
dorsal root ganglion
66
what is in the dorsal root ganglion
sensory nuclei
67
sensory pathways
sensory signals travel from sensor organ or tissue up axon of peripheral sensory nerve nuclei in DRG
68
first order neuron
one axon travels from sensor organ to DRG which projects an axon towards the spinal cord and synapses in the dorsal horn of the spinal cord
69
second order neuron
travel up spinal cord in sensory tracts of white matter and synapse in thalamus
70
third order neuron
synapses with thalamus and projects into sensory cortex
71
where is primary somatosensory cortex
post-central gyrus in parietal lobe of cerebrum
72
sensory pathways carry info about...
touch (fine and crude) pain temp proprioception special sense (audition, vision, olfaction, taste)
73
ascending tracts to know
dorsal columns spinocerebellar tracts spinothalamic tracts
74
dorsal columns are what kind of tract
sensory - ascending
75
spinocerebellar tracts are what type of tract
sensory - ascending
76
spinothalamic tracts are what type of tract
sensory - ascending
77
dorsal columns carry info about...
fine touch - two point discrimination vibration conscious proprioception
78
where do dorsal columns decussate
medulla
79
neurons in dorsal columns
- 2nd order neuron crosses over (in medulla - medial lemniscus) not the dorsal columns - 1st order neuron in dorsal column, 2nd order neuron in medulla decussates taking info to thalamus, 3rd order neuron to somatosensory cortex (post-central gyrus)
80
spinocerebellar tracts
unconscious proprioception and balance ventral and dorsal tract
81
spinothalamic tracts sense...
pain temp gross touch/pressure
82
how many spinothalamic tracts
2 (lateral and ventral)
83
where do spinothalamic tracts decussate
at the level of the spinal cord (roughly where the sensory neuron enters)
84
what are spinal reflexes and their role?
- Automatic, involuntary and rapid - Protective function - Can be used to test for level of deficit - Sensory (central and peripheral deficit) - Damage to spinal cord at a level - Damage to brain (brainstem reflexes)
85
what happens at posterior horn of spinal cord?
sensory/afferent signals arrive at the cord
86
what happens at anterior horn of spinal cord?
motor signals leave the cord
87
example reflex - standing on a pin
nociceptors in skin transduce mechanical energy into electrical energy in form of AP. AP passes up somatic sensory nerves in foot and leg towards spinal cord sensory neurons passes into dorsal horn of spinal cord and synapses in grey matter with a control centre (relay/interneuron) interneuron relays electrical signal directly to motor neuron which leaves ventral horn and travels down spinal nerve to target muscle. foot is drawn away from the pin.
88
biology behind a reflex to prevent damage
prevent muscles from damage by stretching too much - muscle spindle receptors in muscle detect stretch and send afferent neurons to spinal cord which synapse directly with efferent neurons to innervate muscle fibres to connect. (occurs at spinal cord level)
89
reflexes can be...
brisk normal absent
90
bicep tendon reflex root level
C5 C6
91
Triceps tendon reflex root level
C7 C8
92
knee tendon reflex root level
L3 L4
93
ankle tendon reflex root level
S1 S2
94
reflex loss (hyporeflexia/absent) indicates...
peripheral neuropathy LMN lesion
95
hyperreflexia indicates...
damage to motor pathway in brain e.g. stroke or tumour damage to spinal cord above reflex e.g. compression, inflammation, trauma UMN issue
96
signs or cerebellar damage
dysdiadochokinesia ataxia nystagmus intention tremor slurred speed hypotonia
97
dysdiadochokinesia
uncoordinated movements (like touching back of hand and then palm, alternating quick)
98
ataxia
wide gait (walking differences)
99
nystagmus
eyes rapidly moving
100
intention tremor
can't do things like touching your nose and then touch an outstretched finger etc
101
slurred speech
staccato speech
102
hypotonia
tone goes down
103
dermatome
area of skin innervated by a single spinal cord level
104
myotome
muscles served by a spinal nerve route

Neuroanatomy (7 decks)

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