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Neuroanatomy > 3b: Spinal cord > Flashcards

3b: Spinal cord Flashcards

1
Q
  1. ) Which spinal cord segments make the conus medullaris?

2. ) At what vertebral level does it exist?

A
  1. ) S3 to Co.

2. ) L1 or L2.

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2
Q

What unique parts of the spinal cord is lamina IX associated with? Which part of lamina IX?

A

The lateral part of lamina IX is associated with the two spinal cord enlargements: Cervical (C4-T1), and lumbosacral (L1-S2).

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3
Q

What are the most important (i.e. clinically relevant) tracts found within the lateral funiculus and what is their function (4)?

A

1.) Lateral corticospinal tract (descending): Concerned with volitional skilled motor activity, 1˚ of the digits of the upper limb.
2.) Anterolateral system (ALS) —> Spinothalamic tract (ascending): Conscious response to pain; sensation for pain and temperature (hot/cold).
3.) Posterior spinocerebellar tract: Transmits unconscious proprioceptive information to the cerebellum (lower limb coordination; input from spindles).
4.) Anterior spinocerebellar tract: Unconscious proprioception from the lower limb to cerebellum (concerned with coordinated movement and posture).
OneNote, p.109 BRS.

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4
Q

Give the defining characteristics of the cervical spinal cord (3).

A
  1. ) Largest diameter; round to oval-shaped.
  2. ) Posterior intermediate sulci w/ gracile and cuneate fasciculi (ONLY above T6).
  3. ) Massive horns on C4-C8.
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5
Q

Describe which type(s) of fibers enter the dorsal root (1) medial division and (2) lateral division. Also describe where they go within the spinal cord, and their NT.

A

1.) Medial division: Fibers enter the posterior column.
-Proprioceptive fibers (Aα-Ia, Ib): To Clarke’s nucleus in lamina VII (ant. horn), and then to the spinocerebellar tract. NT = Glutamate.
-Exteroceptive fibers (Aβ); discriminative touch, vibration: Enter the posterior column. NT = Glutamate.
2.) Lateral division: Exteroceptive (Aδ), with pain, crude touch, and temperature (hot). Enter via the posterolateral (Lissauer’s) tract, and go to lamina I-V.
Interoceptive fibers (C): Postganglionic SNS, visceral afferent. travel to lamina I, V-VII.
NT= Substance P and CCRP (calcitonin gene-related peptide).
#36

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6
Q

What is the preferred site of a lumbar puncture?

A 
L3-L4 IV space. 
#11
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7
Q

What two things do descending tracts do?

A

1.) Influence motor neurons.
2.) Modulate nociceptive information in posterior horn.
#52

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8
Q

Describe the crossed extension reflex in terms of the four requirements for a reflex arc.

A

Same circuit as flexor reflex, but involves contralateral musculature.
Same stimulus.
Afferents: Aδ or C fibers —> Interneurons, to…
Efferent: Motoneuron of CONTRALATERAL horn —> Inhibition of flexion, and excitation of extension on the contralateral leg = Supports trunk while standing or walking to keep from falling.
#47

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9
Q

Describe flexor reflex in terms of the four requirements for a reflex arc. What type of reflex is it?

A

COMPLEX reflex —> Withdrawal reflex = Protective
Receptor: Nociceptor.
Stimulus: Cutaneous (nociceptive).
Afferent: Aδ or C fibers —> Lissauer’s tract —> Ascend/descend —> Branch —> Tract cell, interneurons (Lamina VIII, excitatory and inhibitory).
Efferents: Tract cell —> Spinothalamic tract —> higher neuraxis.
Effects:
a.) Excitatory interneuron = Contraction of flexors.
b.) Inhibitory interneuron = Inhibition of extensors.
#46

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10
Q

What is characteristic about the gray matter at the thoracic levels (4)?

A

1.) T1-L2 = Clarke’s nucleus.
2.) Above T6 = Posterointermediate sulcus; both gracile and cuneate fasciculi present.
3.) Slender horns.
4.) Lateral horn.
#26

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11
Q

What spinal cord segments correspond with the following vertebral levels?

  1. ) C3
  2. ) T4
  3. ) T8
  4. ) T10
  5. ) T11
  6. ) T12
  7. ) L1
A

1.) C4 cord segment (cervical = +1)
2.) T6 cord segment (T1-6 = +2)
3.) T11 cord segment (T7-9 = +3)
4.) L1-L2 cord segments
5.) L3-L4 cord segments
6.) L5 cord segments
7.) Sacral and coccygeal cord segments
#8

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12
Q

What type of motor fibers are carried to the muscle spindles on γ-motoneurons?

A

Intrafusal.

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13
Q

How do the anterior-, posterior-, and cuneocerebellar tracts enter the cerebellum?

A
  • Anterior via the SUPERIOR cerebellar peduncle.
  • Posterior and cuneocerebellar tracts enter via the INFERIOR cerebellar peduncle.
    pp. 108-109 BRS
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14
Q

Give the vertebral levels of the following:

  1. ) Dural sac
  2. ) Lumbar cistern
A

1.) Foramen magnum –S2
2.) L2 –S2
#9

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15
Q

What structure is closely related both spatially and functionally to Lissauer’s tract?

A 
Substantia gelatinosa (Lamina II). 
#57
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16
Q

What is the role of lamina IX?

A 
Motor neurons for skeletal muscle. 
#23
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17
Q

Which two spinal levels have the largest gray horns?

A

Cervical (C4 to T1) and lumbosacral (L1 to S2) cord levels have prominent posterior and anterior horns because of the extensive sensory input from and motor outflow to the upper and lower extremities.

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18
Q

Describe:

  1. ) Posterior median sulcus
  2. ) Posterolateral sulcus
A
  1. ) Separates the posterior portion of the cord into halves and contains a delicate layer of pia, the posterior median septum.
  2. ) Represents the entry point of posterior root (sensory) fibers. This area is frequently called the posterior (dorsal) root entry zone. Runs the full length of the cord.
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19
Q

Which type(s) of sensory only nerve fibers are unmyelinated?

A 
IV (C). 
#33
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20
Q

Which lamina possesses large motor neurons? Where is it in terms of gray matter?

A

Lamina IX in the anterior/ventral horn of gray matter.

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21
Q

What are the spinal segments of the two enlargements?

A

Cervical: C4-T1
Lumbar: L1-S2
41, 12
L3b, #6

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22
Q

What are the fibers called that supply VA innervation to the visceral/internal organs (e.g. bladder)?

A 
Introceptive = Sensory fibers from internal organs. 
#34
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23
Q

Concerning Lamina IX within the anterior horn: What are the roles of the neurons in the (1) medial group, (2) the lateral group, and (3) the central group?
4.) Of the lateral group, which parts are for flexors, and which are for extensors? Distal and proximal?

A

1.) Medial: Axial musculature of head and neck (axial is kind of medial, compared to appendicular).
2.) Lateral: Limb musculature (L = Limb). Only related to the enlargements (C4-T1, L1-S2)
3.) Central: Phrenic (C3-C5), and Spinal accessory (C1-C5).
4.) The posterior portion is for flexors, the anterior is for extensors. The posterior-most portion of each group is for distal musculature, the anterior-most portion of each is for proximal musculature.
#22

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24
Q

Where does sensation that travels on the lateral spinothalamic tract enter the spinal cord?

A 
Through the lateral division of the dorsal root via Lissauer's tract. 
#53
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25
Q
  1. ) What motor components will be carried in the sacral spinal levels?
  2. ) Coccygeal?
A

1.) Visceromotor; i.e. GVE (S2-S4, PSNS), and somatic motor GSE (SE) in the anterior horn.
2.) Just GSE and GSA.
#34

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26
Q

What is characteristic of the gray matter in the lumbar spinal cord levels?

A

1.) Larger horns (than thoracic), with proportionally less white matter.
2.) Clarke’s nucleus —> until L1,2.
3.) Lateral horn up to L1.
#27

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27
Q

What is unique about the white matter in the cervical spinal cord segments (3)?

A

1.) Largest amount of white matter of any segment.
2.) BOTH gracile and cuneate fasciculi.
3.) Posterior intermediate sulci: Separates gracile from cuneate –only present above T6.
#25

28
Q
  1. ) Where does the rubrospinal tract cross?

2. ) What does it do?

A

1.) Crosses in midbrain.
2.) Contraction of flexors, inhibition of extensors.
#64

29
Q

Which lamina possesses interneurons? Where is it in terms of gray matter?

A

Lamina VIII in the anterior/ventral horn.

30
Q

Which types of fibers enter the lateral division of the posterior root (2)? Where do they go? What is their NT (2)?

A

Aδ and C fibers
1.) Exteroceptive fibers: Pain, crude touch, temp. —> to Lissauer’s/Posterolateral tract —> Lamina I-V (terminates here).
2.) Interoceptive fibers: Visceral afferent —> Sympathetic fibers —> Lamina I, V-VII (terminates here…WHY?).
Neurotransmitter = Substance-P, CCRP (calcitonin gene-related peptide)
L3b, #36 (p.131)

31
Q

What are the second order neurons of the DCML? Where are they located? What happens here?

A

Gracile and cuneate nuclei in the CAUDAL MEDULLA. Here, the dorsal column fibers decussate and become the medial lemniscus.
p.104 BRS

32
Q

What type of neurons does the intermediate/lateral horn possess? At what spinal cord levels are they found?

A 
Preganglionic sympathetic neurons –T1-L2. 
#26
33
Q

Name all of the nuclei associated with Lamina VII (3), along with their spinal cord levels.

A

1.) Clarke’s nucleus (T1-L2)
2.) Intermediolateral nucleus (T1-L3; lateral horn): IMLs.
3.) Sacral parasympathetic nucleus (S2-S4).
#23

34
Q

Give the defining characteristics of the lumbar spinal cord (4).

A
  1. ) Minimal white matter.
  2. ) Large gray horns.
  3. ) Clarke’s nucleus at L1,2.
  4. ) Lateral horn up to L1.
35
Q

What are two other pathways carrying nociceptive and touch sensation?

A

1.) Postsynaptic posterior column (along posterior funiculus).
2.) Spinocervicothalamic: Lateral funiculus in the posterior aspect next to lateral CS tract.
#59

36
Q

Which emerges first from the mixed spinal nerve: White or gray rami communicantes?

A 
Gray, then white.
#31
37
Q

How many pairs of denticulate ligaments are there? What are they formed from ?

A 
21 —> formed from pia mater; connects spinal cord to the dura. 
#10
38
Q

Where is Clarke’s nucleus and what does it do?

A

Clarke’s Nucleus is in lamina VII of the intermediate zone from T1-L2 spinal segments.
-Important in relaying information about position of lower limb to the cerebellum.
-Origin of the posterior spinocerebellar tract.
(L3b #21)

39
Q

What accounts for the large size of the posterior horns in the lumbar spinal cord levels?

A

Accommodation for the significant sensory input from, and motor output to the lower limbs.
p.128 text

40
Q

Which cervical spinal cord levels have the largest gray horns? Why?

A

C4-C8 are very large because of the enlargement at these segments. This reflects the sensory input from, and the motor innervation to the upper extremity.
p.128 text

41
Q

Give the defining characteristics of the sacral spinal cord (5).

A
  1. ) Round and small.
  2. ) Surrounding roots.
  3. ) Thin shell of white.
  4. ) Sacral viscero-motor nuclei (S2-S4) in gray.
  5. ) Obvious Lamina II in dorsal horn.
42
Q

What are the motor components of a spinal nerve (1 a and b, 2)? What is their NT? Where do each enter the spinal cord?

A

1.) Somatic Efferent:
(a) Alpha motor neurons —> to EXTRAfusal fibers (Aα).
(b) Gamma motor neurons —> to INTRAfusal fibers (Aγ).
2.) Visceral efferent
Neurotransmitter = ACh
Aα: Enter spinal cord at LATERAL division of posterior root, and ascend or descend in the posterolateral tract (of Lissauer). aLpha = Lateral
Aγ: Enter in the MEDIAL division of the posterior root. gaMma = Medial
L3b, #39

43
Q
  1. ) What are the spinal cord segments of the filum terminale externum?
  2. ) Which nerve roots are contained within the lumbar cistern?
A

1.) S2-Co1
2.) L2-Co1
#13

44
Q

Describe the positioning of fasciculi gracilis and cuneatus relative to one another, and at what spinal segments they are found. What are they responsible for?

A
  1. ) Fasciculus Gracilis: Medial to cuneatus; found at ALL cord levels. Sensory to lower limbs.
  2. ) Fasciculus Cuneatus: Lateral to gracilis; found ONLY between C1-T6. Sensory to upper limbs.
    p. 100 BRS
45
Q
  1. ) How does sensation reach the spinothalamic tract?

2. ) Where do the cervical and coccygeal fibers lie in relation to one another?

A

1.) Enters the brainstem via Lissauer’s tract —> Ascends or descends 1-2 levels —> Crosses at anterior white commissure —> ALS.
2.) Cervical = AnteroMEDIAL, Coccygeal = PosteroLATERAL.
#56

46
Q

Which lamina is associated with motor neurons? What are the nerves (2)?

A

Lamina IX:
1.) Phrenic (C3-5)
2.) Spinal accessory (C1-C6)
#23, p.100 BRS

47
Q

What disorder causes clasp knife rigidity? What is the result? What is the physiologic cause?

A 
Caused by UMN disorder = Rapid decrease in resistance on attempting to stretch a muscle. 
-Autogenic inhibtion initiated by Golgi tendon organs. 
#48
48
Q

Which types of fibers enter the medial division of the posterior root (2)? Where do they go? What is their NT?

A

1.) Proprioceptive fibers (Aα –Ia, Ib): To dorsal/posterior column/Clarke’s nucleus/anterior horn.
2.) Exteroceptive fibers (Aβ): Discriminitive touch, vibration —> to Posterior column.
Neurotransmitter = GLUTAMATE
These fibers give rise to the ascending or descending collaterals…(what does this mean?)
L3b, #36, (p.131)

49
Q

What is the role of lamina VIII?

A

Interneurons and tract cells.

50
Q

What is the type of afferent neuron utilized in the reciprocal inhibition reflex? In which lamina is it located? Which NT is used and why?

A 
Type Ia neuron; an INTERNEURON in lamina VIII of the anterior/ventral horn. Glycine (inhibitory) is its NT because it inhibits the antagonist muscle, thereby increasing the effectiveness of the stretch reflex.
#44
51
Q

What are the consequences of both upper (3) and lower (5) motor neuron injuries?

A

1.) UMN lesion (above anterior horn neurons): Spastic paralysis; increased tone and reflexes.
2.) LMN lesion (anterior horn/peripheral nerve): Flaccid paralysis; decreased tone and reflexes, muscle atrophy, fasciculations (def. a brief, spontaneous contraction affecting a small number of muscle fibers, often causing a flicker of movement under the skin).
#63

52
Q

Give the defining characteristics of the thoracic spinal cord (4).

A
  1. ) Smaller than cervical.
  2. ) No posterointermediate sulcus below T6.
  3. ) Slender gray horns.
  4. ) Clarke’s nucleus (T1-L2) w/ IMLs.
53
Q

What does Lissauer’s tract become as it enter the hindbrain?

A

As it enters the hindbrain, Lissauer tract becomes the spinal trigeminal tract.

54
Q

What are two key characteristics of the gray matter in the sacral spinal cord levels?

A
  1. ) S2-4 contains preganglionic PSNS cell bodies (the visceromotor nucleus).
  2. ) Substantia gelatinosa is especially prominent in Lamina II in the sacral spinal cord levels.
    p. 128 text
55
Q

Where do sensory fibers enter the spinal cord?

A

Posterolateral sulcus; also called the posterior (dorsal) root entry zone. Runs the full length of the cord

56
Q

What is the purpose of propriospinal fibers?

A 
To connect various spinal levels — INTRASPINAL REFLEXES (complex).
#52
57
Q

What nerve roots make up the filum terminale externum?

A 
S2-Co
#13
58
Q

What parts of the body contribute to the thoracic spinal cord levels?

A 
JUST THE TRUNK — *no contribution TO OR FROM the limbs*
#26
59
Q

Describe autogenic inhibition (i.e. inverse myotactic reflex) in terms of the four requirements for a reflex arc.

A

Receptor: Golgi tendon organ
Stimulus: Stretch (over-stretching, in this case).
Afferent: Ib fiber.
Interneuron: Group Ib gylcinergic (inhibits motoneuron).
Target: Stretched muscle.
Effect: Relaxation of target muscle.
Function: Maintains normal muscle tone
#45

60
Q

List the Rexed Lamina of the dorsal horn associated with SENSORY FUNCTIONS (6), the cells/nuclei they contain, and their function(s).

A

Lamina I – Posteromarginal nucleus: Associated with light touch, pain, and temperature sensation; origin of some fibers of anterolateral system.

Lamina II –Substantia gelatinosa: Homologous to the spinal trigeminal nucleus. Modulates pain and temperature transmission.

Lamina III and IV –Nucleus proprius: Associated with light touch, pain, and temperature sensation; origin of some fibers of anterolateral system.

Laminae V and VI form the base of the posterior horn, and are usually divided into medial and lateral portions (p.127 text). BUT WHAT IS THEIR FUNCTION???

61
Q

What are the four requirements for a spinal reflex?

A

1.) Afferent neuron
2.) Interneuron
3.) Motor/efferent neuron
4.) Target tissue
#42

62
Q
  1. ) What type of fibers project from the alpha motoneurons?
  2. ) Gamma motoneurons?
  3. ) What is their NT?
A
  1. ) Extrafusal (Aα).
  2. ) Intrafusal (Aγ).
  3. ) NT = ACh.
63
Q

What re the NTs for the lateral and medial dorsal root divisions?

A 
Medial = Glutamate.
Lateral = Substance P or CCRP (calcitonin gene-related peptide). 
#36
64
Q

At cervical levels are the gray horns largest?

A 
C4-C8
#25
65
Q

Where do the preganglionic visceral efferent fibers arise from (2)?

A

1.) SNS —> IMLs (T1-L2).
2.) PSNS —> Sacral visceromotor nucleus (S2-S4).
L3b, #40

66
Q

What type of afferent fibers are used in the deep tendon/stretch reflex?

A 
Heavily myelinated, rapidly conducting *group Ia fibers.*
#43, p.132 text
67
Q

What neurotransmitter do inhibitory interneurons use?

A

Glycine = Glycinergic neurons.

p.133

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