spinal cord segmental organization Flashcards

1
Q

Where is the posterior median sulcus?

A

posterior/dorsal surface

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2
Q

Where is the posterior lateral sulcus?

A

dorsal root entry zone (sensory)

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3
Q

Where isq the anterior median fissure?

A

anterior/ventral midline

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4
Q

Where is the anterior lateral sulcus?

A

exit anterior (motor) roots

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5
Q

What is the dorsal (posterior) root ganglion?

A

give rise to central and peripheral nerve fibers.

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6
Q

Where is the central canal located?

A

In the gray commissure

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7
Q

Where can we find lateral gray horn?

A

in thoracic & upper lumbar segments of the cord

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8
Q

Into what is the white matter divided?

A

columns or funiculi

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9
Q

What are the columns of the spinla cord?

A

dorsal (posterior) column
lateral column
ventral (anterior) column

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10
Q

identify

A

cervical

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11
Q

identifyq

A

thoracic

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12
Q

identify

A

lumbar

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13
Q

identify

A

sacral

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14
Q

What are the type of neurons in the gray matter?

A

Local interneurons
Commissural neurons
Propriospinal neurons

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15
Q

What are local interneurons?

A

axons remain on ipsilateral (same
side) gray matter within a cord
segment

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16
Q

What are commissural neurons?

A

axons cross midline to
terminate in contralateral
(opposite side) gray matter

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17
Q

What are propriospinal neurons?

A

axons project rostrally (superiorly) or caudally (inferiorly) in surrounding
white matter for several segments before terminating in gray matter

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18
Q

What are interneurons?

A

-Majority of spinal neurons
-Receive information from primary sensory afferents, dorsal horn neurons, motor neurons, & descending pathways
-Integrate segmental activity that
controls spinal sensory processing &
motor and autonomic outputs
-May have excitatory or inhibitory effects on other spinal neurons
(excitatory neurons are glutamatergic)
(inhibitory neurons are GABAergic or glycenergic)

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19
Q

What are second order sensory neurons?

A

Projection neurons:
neurons which are glutamatergic and project axons from the dorsal and
intermediate gray horn to the thalamus, brainstem or cerebellum

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20
Q

What are cholinergic (acetylcholine) motor neurons?

A

Projection neurons:
located in the ventral horn and project
to skeletal muscle

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21
Q

What are cholinergic autonomic preganglionic neurons?

A

located in the intermediate gray matter and project to autonomic ganglia.

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22
Q

Where is the dorsomarginal nucleus found?

A

all cord levels in lamina I

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23
Q

What type of sensations does dorsomarginal nucleus has?

A

light touch (non-specific), pain and temperature sensations

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24
Q

What does dorsomarginal nucleus contain?

A

contains somas of 2nd-order sensory neurons that project to the thalamus

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25
Where is the substantia gelatinosa found?
found at all cord levels (mostly in lamina II
26
What type of sensations does substantia gelatinosa has?
mostly pain, some touch and temperature sensations
27
What does substantia gelatinosa contain?
somas of 2nd-order sensory local interneurons that integrate inputs from primary sensory neurons to modulate sensations; projects to other lamina, thalamus and other parts of brain
28
Where is the nucleus propius found?
found at all cord levels (mostly in laminas III & IV)
29
What type of sensations does nucleus propius has?
light touch, pain & temperature sensations
30
What deos nucleus propius contains?
contains somas of 2nd-order sensory neurons that project to the thalamus and other parts of brain
31
Where is the Nucleus Dorsalis of Clarke (posterior thoracic nucleus) located?
Lamina VII; found at spinal levels (C8)T1-L2 (L3), at the base of dorsal horn or the intermediate gray matter
32
What is the function of the nucleus dorsalis?
associated with unconscious propioception (muscle spindles & gogli tendon organs)
33
Whar does the nucleus dorsalis contain?
contains somas of 2nd-order sensory neurons that project to the cerebellum
34
Where is intermediolateral nucleus located?
found at spinal levels ~T1-L2 (Lamina VII)
35
what does intermediolateral nucleus contain?
-contains somas of preganglionic sympathetic motor neurons (GVE) that project to sympathetic ganglia -contains, at T1-T2, the ciliospinal nucleus (center of Budge), source of sympathetic innervation of eye
36
Where are somatic motor nuclei found?
Lamina VIII & IX; Found at all spinal levels
37
wHAT DOES SOMATIC MOTOR NUCLEI INCLUDE?
Include nuclei for specific motor nerves, such as the: 1. Spinal Accessory Nucleus –extends from C1-C6 and gives rise to the spinal root of the spinal accessory nerve (Cranial nerve XI) 2. Phrenic Nucleus –extends from C3 to C6 and gives rise to the phrenic nerve
38
Where is the sacral parasympathetic nucleus found?
1. found at spinal levels S2-S4 2. contains cell bodies of preganglionic parasympathetic motor neurons (GVE) that project to ganglia of the pelvic viscera
39
Explain the distribution of somatic motor nuclei in terms of innervation
-More dorsal nuclei in ventral horn innervate flexor muscles -More ventral nuclei in ventral horn innervate extensor muscles -medial nuclei innervate axial (proximal) muscles or trunk musculature -lateral nuclei innervate appendicular (extremities) or distal musculature
40
What are the dorsal columns ascending pathways?
Fasciculus Gracillis Fasciculus Cuneatus
41
What are the lateral columns ascending pathways?
Dorsal Spinocerebellar tract Ventral Spinocerebellar tract Lateral Spinothalamic tract
42
What are the lateral columns descending pathways?
Lateral Corticospinal tract Rubrospinal tract
43
What are the ventral columns ascending pathways?
Ventral Spinothalamic tract
44
What are the ventral columns descending pathways?
Ventral Corticospinal tract Reticulospinal tract Vestibulospinal tract Tectospinal tract
45
What are the two pathways in spinal cord for somatic sensation?
-posterior column pathway (propioception, vibration, fine/epicritic, discriminative touch); -anterolateral pathway (pain, temperature & crude touch).
46
Explain the descending tracts generally
-Control of skeletal muscle via descending pathways (e.g. corticospinal tract) include: Upper motor neurons (UMNs): cell body is in brain (i.e. cortex or cerebellum) that projects via axons through white matter to brain stem and spinal cord. UMNs synapse onto lower motor neurons (LMNs) in anterior horns of the central gray matter of brainstem motor nuclei or in spinal cord. Axons of LMNs project out of CNS via anterior spinal roots or cranial nerves to reach muscle in periphery.
47
Explain the somatosensory afferent fiber type Ia
Aa thick; fast 70-120m/sec; propioception (muscle spindles)
48
Explain the somatosensory afferent fiber type Ib
Aa thick; fast 70-120m/sec; propioception (golgi tendon organs)
49
Explain the somatosensory afferent fiber type II
AB moderate; moderate 30-70m/sec; Touch, pressure, stretch, vibration (cutaneous mechanoreceptors), propioception (muscle spindles and joint capsule)
50
Explain the somatosensory afferent fiber type III
Ag; thin; moderate 12-30m/sec; touch , pressure, stretch, fast pain and temperature
51
Explain the somatosensory afferent fiber type IV
C (unmyelinated); very thin; slow (0.5-2m/sec); slow pain and temperature
52
Explain the visceral afferent fiber type III
Ag: thin; moderate (12-30m/sec); visceral sensation (stretch, pain, chemoreception, ischemia)
53
Explain the visceral afferent fiber type IV
c (unmyelinated); very thin, slow (0.5-2m/sec); visceral sensation (stretch, pain, chemorception, ischemia)
54
Explain the somatic efferent fiber LMN Alpha
Aa; thick; moderate to fast (15-120m/sec); innervate extrafusal muscle fibers
55
Explain the somatic efferent fiber LMN Gamma
Ay; Thin; moderate (10-45m/sec); innervate intrafusal muscle fibers
56
Explain the visceral efferent fiber LMN B
Myelinated; thin -very thin; moderate to slow (3-5m/sec); pregangionic autonomic fibers
57
Explain the visceral efferent fiber LMN C
Unmyelinated; very thin; slow 2m/sec; postganglionic autonomic fibers
58
What do Alpha LMN do?
generates force with contraction
59
What does Gamma LMN do?
mechanosensory to detect stretch
60
WHst is the motor end plate?
Where alpha motor neurons project the axons to extrafusal fibers forming a specialized synapse
61
What are motor units?
An alpha (⍺) motorneuron, its axon and all the muscle fibers it innervates
62
What do small motorunits innervate?
motorneuron innervates few muscle fibers (i.e. 10-100) for small muscles (e.g. extraocular muscles)
63
What do large motorunits innervate?
motorneuron innervates many muscle fibers (i.e. 600-1000) for large muscles (e.g. quadriceps muscles)
64
What are intrafusal fibers?
muscle spindles and specialized sensory organs embedded in skeletal muscle
65
What are the two components of the intrafusal fibers and by what are they innervated?
◦ Nuclear bag fiber (innvervated by Ia sensory fiber) ◦ Nuclear chain fiber (innvervated largely by II sensory fiber)
66
What does the intrafusal fibers responds to?
Responds to stretch/length change provding signal to CNS
67
Which part of intrafusal fibers are contractile?
polar ends; central regions are non-contratile
68
Where do Ia & II sensory endings originate?
center region of intrafusal fibers
69
What innervates contractile polar ends of intrafusal fibers?
Gamma y-motor neurons
70
explain what happens when muscle is stretched
When muscle is stretched, muscle spindle intrafusal fibers & sensory endings are also stretched, resulting in increased activity in afferent fibers
71
What is a spinal reflex?
involves excitation of a motor neuron in response to afferent stimulation. They become exaggerated when there is damage to descending pathways. (UMN)
72
What is the golgi tendoon relfex?
inverse myotatic reflex; Resist sustained contraction of a muscle to protect tendon from damage during contraction of the muscle
73
how is the contrcation of the golgi tendon reflex?
Ipsilateral: contraction of a muscle results in inhibition of contraction of same (homonymous) muscle on same side
74
What is the afferent limb for golgi tendon reflex?
Ib sensory neurons
75
What is the efferent limb for golgi tendon reflex?
alpha (a) motor neuron
76
What is the effcetor of golgi tendon relfex?
extrafusal fibers of skeletal muscle where activated GTO is found
77
WHich fibers work in the afferent sense for the golgi tendon and how?
Ib fibers from GTO project to spinal cord where they excite inhibitory interneurons to inhibit α-motor neurons for that muscle (modulation of cortivospinal and bulbospinal pathways)
78
WHat is the flexor withdrawal reflex?
Quickly withdraw a limb from a painful or noxious stimulus (i.e. withdrawal reflex). Reception of painful or noxious stimulus results in contraction of flexor muscles on same side sensory information is received
79
Which sensory neurons detect noxious stimuli y flexor withdrawal reflex AFFERENT LIMB/SENSORY?
III (Aδ) and IV (C) sensory neurons detect noxious stimuli
80
Which sensory neurons detect noxious stimuli y flexor withdrawal reflex EFFERENT LIMB/SENSORY?
⍺-motor neuron
81
What is the effector of the flexor withdrawal reflex?
excite extrafusal fibers of flexor muscles on limb where nociceptors have been activated, and inhibit extensor muscles. Modulation – corticospinal & bulbospinal pathways
82
What happens when there is activiation of inhibitory interneurons in the flexor withdrawal reflex?
Inhibition of motor neurons that innervate extensor muscles
83
What happens when there is activiation of non-inhibitory interneurons in the flexor withdrawal reflex?
Excitation of motor neurons that innervate flexor muscles (agonist & synergist)
84
What is the crossed extension reflex?
Postural support & balance during withdrawal of limb due to painful stimulus Contraction of extensor muscles in opposite limb counteracts increased load caused by withdrawing limb.
85
By what is the crossed extension reflex mediated?
Mediated via interneurons that send collaterals through the ventral gray commissure to make connections with α-motor neurons.
86
Explain the crossed extension reflex
Excitation of motor neurons innervating CONTRALATERAL extensor muscles Inhibition of MNs innervating CONTRALATERAL flexor muscles
87
WHta is the alpha gamma coactivation?
Since muscle spindles are organized in parallel with extrafusal muscle fibers, during voluntary movement it is necessary to activate gamma fibers simultaneously to maintain tension in intrafusal fiber; able for intrafusal fibers to detect muscle length change
88
what is the gamma loop?
refers to movements initiated by descending supraspinal influences (i.e. cortical spinal tract) that activate gamma motor neurons
89