A 11 Spinal Cord Pathways

Question 1

What laminae in the spinal cord does the spinothalamic 1st order neuron synapse on? What might it ascend before doing so?

Answer 1

• Laminae 1,4,5,6 for A Delta’s

- Lamina 2 for SOME C fibers

Question 2

What is the function of the raphespinal tract?

Answer 2

-Autonomics, thermoregulation, pain modulation, and adrenal gland secretion of epinephrine (damage=Horner’s syndrome)

Question 3

What 3 nuclei does the bulbospinal tract come from?

Answer 3

• Periaqueductal gray (PAG) in midbrain
• Locus Ceruleus in pons
• Nucleus Raphe Magnus in medulla (synapse from PAG)

Question 4

The the acronym TINNTING mean?

Answer 4

It describes the 8 different ways that causes lesions of neurons.

1) trauma
2) ischemia
3) neoplasm
4) neurodegenerative diseases
5) Toxins
6) Infection
7) Nutritional deficiencies
8) Genetic

Question 5

pain, temperature and crude touch is mediated through which systems?

Answer 5

1) spinothalmic (from body)

2) trigeminothalmic (from head)

Question 6

discriminative touch and conscious proprioception is mediated through which systems?

Answer 6

1) DCML (from body)

2) Trigeminothalmic (from head)

Question 7

Non-conscious proprioception is mediated through which systems?

Answer 7

1) Dorsal spinocerebellar
2) Ventral spinocerebellar
3) Cuneocerebellar

Question 8

motor to the head is through which system? Is it autonomic of voluntary?

Answer 8

cortical bulbar

Its voluntary motor

Question 9

motor to the body is through which system?

Answer 9

cortical spinal

Question 10

Which areas fine tune/adjust the motor function?

Answer 10

1) cerebellum

2) basal ganglia

Question 11

pain, temperature, itch, and tickle come from follow which tract?

Answer 11

spinothalmic tract

Question 12

where do the secondary axons from the spinothalmic tract cross? Where to they synapse?

Answer 12

They cross through the ventral white commisure at the level that they enter. They first synapse in the dorsal grey horn, cross, then go to the thalamus.

Question 13

discriminative touch, conscious proprioception, and visceral pain from the body follow which tract?

Answer 13

DCML

Question 14

Which nerve fibers run in fasciculus gracilis?

Answer 14

first order neurons of DCML below T-5

Question 15

which nerve fibers run in fasciculus cuneatus?

Answer 15

first order neurons of DCML originating at or above T-5

Question 16

where do the axons of the DCML pathway synapse? Where do the fibers cross?

Answer 16

1st= medulla in gracilis or cuneatus nucleus.

The secondary fibers cross in the medulla after synapsing in the nuclei.

Question 17

signs of a lesion in the DCML system would include?

Answer 17

diminution of the following;
2 point discrimination
vibration sense
limb position

Question 18

Information in the spinocerebellar tracts mainly comes from where?

Answer 18

muscle spindles

GTO

Question 19

T/F Lesions of the spinocereballar tracts do not usually produce any obvious signs?

Answer 19

True, although lateropulsion (walking to one side) can occur.

Question 20

The corticospinal system innervates lower motor neurons and influences mostly what?

Answer 20

The hand muscles.

Question 21

The corticobulbar system innervates cranial nerves and innervates mostly what?

Answer 21

face, jaw, and tongue muscles for speech.

Question 22

where do corticobulbar fibers synapse?

Answer 22

on cranial nerve motor nuclei in the brain stem. All nuclei are innervated bilaterally except for the facial nerve nucleus.

Question 23

where do corticospinal fibers cross?

Answer 23

The majority (90%) cross in the decussations of the medulla, but the rest remain on the same side and eventually cross in the ventral white commisure where they control.

Question 24

where do the corticospinal fibers synapse? (AKA upper motor neurons)

Answer 24

They synapse in the ventral horn of the spinal cord to the lower motor neurons.

Question 25

Lesions in UMN’s result in?

Answer 25

paresis (weakness)
hypertonia & hyperreflexia (b/c loss of inhibition)
Return of the babinski sign. (recall babinski goes away because of myelination of the UMN)

Question 26

where do all of the common effector motor neurons converge to innervate a group of muscles?

Answer 26

Lower motor neurons (all motor pathways eventually converge on LMN from all levels)

Question 27

A lesion of LMN’s would result in what characteristics?

Answer 27

1) weakness
2) paralysis
3) atrophy
4) loss of reflex
5) fasciculations

Question 28

What size fibers are the 1st order neurons in the dorsal spinocerebellar tract and cuneocerebellar tract? The ventral spinocerebellar tract?

Answer 28

• 1a and 1b

- 1b

Question 29

Clarke’s nucleus if found at what levels?

Answer 29

C8-L3 (Dorsal Spinocerebellar)

Question 30

Lesion above what level results in spastic bladder?

Answer 30

• T12 (L1/L2 cord level)
• Below this level results in flaccid (atonic) bladder
• Bowel control follows the same pattern

Question 31

At what levels is Onuf’s nucleus located?

Answer 31

-S1-S4

Question 32

Damage to S1-S4 would destroy ability to empty bladder by destroying somatic bladder control, visceral, or both?

Answer 32

Trick! Only parasympathetics empty the bladder. (S2-S4). (This would occur in cauda equina and conus medullaris syndrome) However:
-Somatic=Onuf (think pudendal) allows control of urethral & bowel sphincters