Spinal Lemniscus

Question 1

what is the 1st order neuron of the spinal lemniscus

Answer 1

located in dorsal root ganglion

Question 2

what are the sensory receptors for the spinal lemnisucs pathway

Answer 2

• free nerve endings/ low myelenated a delta fibres- fast transmission of pain/temp
• Unmyelanated C fibres- for slow transmission of pain/temp

Question 3

Where will the tract go after the 1st order neuron

Answer 3

travel thru dorsal horn and project right to lamina or ascend 2/3 levels (dorsolateral tract of lausseur)1

Question 4

What is the second order neuron of the spinal lemnsicus and what is it supplied by

Answer 4

lamina 1, 3/4, 5/6

supplied by post spinal aa

Question 5

What is the difference in projection of lamina 1 and 3/4

Answer 5

1- signals associated w faster transmissin (pain) synapse in 1 then cross midline thru ant commisure

3/4- associated with lower transmission/uncertain signals, connects with lamina 2 to modulate pain, will then cross ant commisure

Question 6

Somatotopy of anterolateral system

Answer 6

LE enters first and occupies pos laterally, trunk medially and UE most ant position

Question 7

What are the collaterals of the anterolateral system as it ascends thru brainstem (2)

Answer 7

Raphe reticular nuclei- send axons back down + CL to lamina 2

Periaquaductal grey- in midbrain to produce endogenous opiods

Question 8

Where is the 3rd order neuron of the spinal lemnisucs

Answer 8

VPL in thalmus

Question 9

Path of axons from 3rd order neuron and end point

Answer 9

-ascend through post limb and contribute to post central gyrus

Question 10

Blood supply @- Spinal cord, medulla, pons, midbrain

Answer 10

Spinal cord- post spinal
medulla- PICA
pons- long penetrating of basilar
midbrain- Post cerebral

Question 11

Blood supply @- Post limb, post central, paracentral

Answer 11

post- Deep br of middle cerebral
post central- Cortical br of middle cerebral
paracentral- cortical br of collosomarginal (ant)

Question 12

Anterolateral quadrant lesion in spinal cord

Answer 12

Loss pain/temp/crude beginning about 2 levels below lesion CL

Question 13

Lesion in medula (3)

Answer 13

• Loss of pain/temp CL
• Dysarthria, dysphagia, vertigo ataxia (ambiguous n + vestibular nuc)
• IL horners (sympathetic fibres)

Question 14

Lesion in pons

Answer 14

• loss of pain/temp/ touch /proprioception CL

- Facial n and mascatory nucleus (trigeminal) may be impaired IL

Question 15

Lesion in midbrain

Answer 15

-loss of pain/ thermal/touch/proprioception CL

Question 16

Lesion in thalmus/post limb

Answer 16

Loss of all sensations CL to lesion

Post limb- will also lose voluntary motor control CL

Question 17

Lesion in postcentral/paracentral gyrus

Answer 17

loss of sensation CL (depending on Loc)

Question 18

What does syringomielia cause

Answer 18

Bilateral loss of pain and temp loss @ lvl of the lesion (cape like pattern)- other sensations ok

-due to disrupting decusating fibres

Question 19

What is brown sequard syndrome and what does it cause

Answer 19

hemisection of spinal cord

• IL loss of vibration/fine touch/proprioception + motor loss
• CL loss of pain and temp 2/3 levels below lesion CL