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Neuro 5 Flashcards

1
Q 
Posterior column- medial lemniscus pathway
Spinothalamic tract (anterolateral pathway)
A

terminate in cortex – we have consciousness of them.

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2
Q

Posterior spinocerebellar tract
Cuneocerebellar tract
Anterior spinocerebellar tract

A

they terminate in cerebellum – we have no consciousness of them

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3
Q

Ascending and Descending Pathways

A

Consists of three general types:
Long, ascending fibers going to thalamus, cerebellum or various brainstem nuclei
Long, descending fibers going from cerebral cortex or various brainstem nuclei to spinal cord gray matter
Short, propriospinal fibers interconnecting different spinal cord levels
These fibers help coordinate flexor reflexes

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4
Q

Fibers with similar connections (destinations) tend to

A

travel together and form tracts in the spinal cord

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5
Q

Ascending tracts found in

A

all three funiculi (AF, LF, PF)

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6
Q

Descending tracts primarily located in

A

anterior (AF) & lateral (LF) funiculi

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7
Q

Propriospinal fibers

A

surround the spinal cord gray matter (propriospinal tract)

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8
Q

Somatosensory Receptors

A

Detect mechanical, chemical or thermal changes
All are pseudounipolar neurons with:
Cell body in DRG or cranial nerve ganglion
A central CNS process (spinal cord or brainstem)
Peripheral process with an ending in skin, muscle, or a joint

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9
Q

free nerve endings

A

touch = simple crude touch (brushing up against your arm).

pain, temp

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10
Q

Merkel endings

A

discriminative touch (texture, very fine) (two point discrimination)

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11
Q

Ending around hairs

A

touch

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12
Q

Ruffini ending

A

pressure

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13
Q

meisner corpuscle

A

descriminitve touch (two point descrimination)

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14
Q

Pacinian corpuscle

A

vibration

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15
Q

Obex

A

apex of fourth ventricle where it narrows to the central canal

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16
Q

Pyramidal decussation

A

interrupts anterior median fissure, at junction of brainstem and spinal cord. Contains corticospinal tract, motor fibers from cerebral cortex on their way to the spinal cord. Note pyramid bounded by anterolateral sulcus.

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17
Q

Fasciculus cuneatus

A

extends to cuneate tubercle, marking site of the nucleus cuneatus. Fasciculus gracilus extends to the gracile tubercle which is at the site of nucleus gracilus.

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18
Q

Posterior columns ascend to

A

medulla

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19
Q

Caudal (closed) Medulla

A

Caudal to the 4th ventricle
Spinothalamic tract (STT)
Nucleus and fasciculus gracilis (NG, FG)
Nucleus and fasciculus cuneatus (NC, FC)

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20
Q

Rostral (open) Medulla

A 
Medial lemniscus (ML)
Spinothalamic tract (STT)
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21
Q

Medial lemniscus

A

ascends to thalamus

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22
Q

Posterior column- medial lemniscus pathway

A

Discriminative touch; Mostly ascending large myelinated primary afferents from various mechanoreceptors
Two point discrimination & conscious proprioception
Vibratory sense
Synapses in medulla and then decussates forming the medial lemniscus
Relays in the lateral thalamus
Ventral posterolateral nucleus (VPL)
Terminates in the postcentral gyrus

23
Q

Posterior column- medial lemniscus pathway

A

Spinal afferents have their cell bodies in ipsilateral DRGs
As DRG rootlets enter cord, fibers divide into two divisions:
Medial- heavily myelinated, large diameter fibers; enter posterior column and ascend to brainstem
Lateral- finely myelinated and unmyelinated, small diameter fibers

24
Q

Rostral to T6 few fibers are added to

medial lemniscus pathway

A

fasiculus gracilis, and fasiculus cuneatus starts to form

25
Fibers entering posterior columns are added
laterally to those already present, so a pattern of lamination develops MLP
26
Sacral levels most
medial, and cervical levels most lateral MLP
27
Fibers reach the brainstem and synapse in
nucleus gracilis and cuneatus (posterior column nuclei) MLP
28
Second order fibers cross the midline in
caudal medulla and form the medial lemniscus MLP
29
Third order fibers originate in
thalamus (ventral posterolateral nucleus) ascend thru internal capsule and synapse in primary somatosensory cortex in postcentral gyrus MLP
30
Injury leads to impaired
proprioception and discriminative tactile functions, especially complex tactile discrimination MLP
31
Tested clinically by placing a
vibrating tuning fork on body surface or have patient identify a pattern drawn on them MLP
32
Spinothalamic tract (STT)/ Anterolateral pathway
One of multiple pathways that convey pain and temperature info Involved in awareness and localization of painful stimuli Ultimately ends in VPL of thalamus and some nearby thalamic nuclei Other fibers in this pathway end in reticular formation of limbic system to mediate other pain responses These fibers travel with the spinothalamic tract so some prefer the term anterolateral pathway (in anterior half of lateral funiculus)
33
Spinothalamic tract/ Anterolateral pathway
Pain, temperature and some mechanoreceptor fibers enter cord via lateral division of dorsal root, project branches to posterior horn many synapse in substantia gelatinosa
34
Neurons in posterior horn are
2nd order neurons, axons cross midline with rostral inclination, collect and form anterolateral pathway STT
35
New fibers join at
anteromedial edge STT
36
Somatotopic organization: STT
3Caudal body parts in posterolateral portion, rostral parts in anteromedial portion
37
Spinothalamic fibers
start in posterior horn project to VPL | Medial lemniscus also uses VPL
38
Other spinothalamic fibers project to
intralaminar nuclei and other thalamic nuclei STT
39
Spinoreticular fibers projection to
brainstem reticular formation Likely important for changes in the level of attention of pain response STT
40
Spinomesencephalic fibers are important in
pain control mechanisms STT
41
Spinohypothalamic fibers mediate
autonomic response to pain
42
STT
fibers travel in anterolateral pathway
43
STT Damage causes loss of:
Pain and temperature sensations | Itch and tickle sensations
44
Bowel and bladder pressure, sexual sensations
ascending bilaterally so unilateral injury does not leave a deficit
45
Cordotomy
Destroy spinothalamic tract to produce contralateral analgesia in patients with intractable pain Cut lateral funiculus from dentate ligament to ventral root rostral to highest dermatomal pain level Analgesia lasts several months Cut highest – they have rostral ascension. So if you have to cut lower to get the same effect.
46
Sensory Homunculus
Pathways are somatopically organized
47
Spinal cord information to cerebellum
Information from spinal cord used by the cerebellum to coordinate movement Direct: Spinocerebellar tracts, three are well characterized Indirect: Via brainstem relay nuclei
48
Posterior Spinocerebellar Tract (PSCT)
Convey proprioceptive info Ipsilateral leg proprioception
49
Collaterals from posterior columns convey
tactile, pressure and proprioceptive info (spindles & GTO) synapse in Clarke’s nucleus PSCT
50
Axons ascend ipsilateral
lateral funiculus forming PSCT on cord surface PSCT
51
Fibers enter cerebellum (vermis and adjacent hemispheres) via
inferior cerebellar peduncle PSCT
52
Cuneocerebellar tract
Most spinocerebellar-like fibers that enter in cervical and upper thoracic segments (arm) do not project to Clarke’s nucleus Arm afferents ascend in fasciculus cuneatus to lateral cuneate nucleus in the medulla Axons from lateral cuneate nucleus collect and form cuneocerebellar tract, enters inferior cerebellar peduncle to synapse in vermis and nearby cerebellar hemispheres
53
Anterior Spinocerebellar Tract (ASCT)
Conveys more complex information to cerebellum Origin: lateral surface of anterior horn at lumbar levels (spinal border cells) Primarily concerned with leg but differs from PSCT Inputs more complex (cutaneous receptors, interneurons and from fibers in descending tracts) So ASCT activity more related to attempted movement and not simple sensory signals Note: crosses midline twice, so ultimately fibers end ipsilateral to their source

Anatomy 2 (15 decks)

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