Sensory System Flashcards
What are the modalities of the sensory system?
Temperature Pain Pressure/crude touch Vibration Fine touch Proprioception 2-point discrimination
What are the main tracts of the sensory sytem?
Spinothalamic
Dorsal column
Which modalities are carried by the spinothalamic tract?
Temperature
Pain
Pressure/crude touch
Which modalities are carried by the dorsal column tract?
Vibration
Fine touch
Proprioception
2-point discrimination
Describe the somatic pathway
1st axon
- communicates with receptor
- cell body in dorsal root ganglion
- synapses in ipsilateral cord/medulla
2nd axon
- cell body in cord/medulla
- decussates
- projects to thalamus
3rd axon
- cell body in thalamus
- projects to post central gyrus
What does decussate mean?
Crosses the midline
Describe the lumbar part of the dorsal column medial lemniscus pathway?
Primary neurone
- runs up ipsilateral side to medulla - close to midline
Secondary neurone
- decussates
- projects to thalamus
Tertiary neurone
- projects to medial primary sensory cortex
Which fasciculi are part of the dorsal column medial lemniscus pathway?
Gracile fasciculus - T7 down
Cuneate fasciculus - T6 up
Describe the cervical part of the dorsal column medial lemniscus pathway?
Primary neurone
- ascends ipsilateral side - lateral to lumbar portion
Secondary neurone
- decussates
- projects to thalamus
Tertiary neurone
- projects to lateral primary sensory cortex
What is the medial lemniscus?
Pathway containing secondary neurones running through brainstem
Where do you get signs with a lesion in the dorsal column tract?
Ipsilateral signs below nucleus
Because it decussates in the brainstem
Describe the lumbar part of the spinothalamic tract?
Primary neurone
- synapses in ipsilateral cord at spinal level
Secondary neurone
- decussates
- passes through ventral white commissure
- runs laterally in cord to thalamus
Tertiary neurone
- projects to medial primary sensory cortex
What is the ventral white commissure?
Middle point at the front of spinal cord
Describe the lumbar part of the spinothalamic tract?
Primary neurone
- synapses in ipsilateral cord at spinal level
Secondary neurone
- decussates
- passes through ventral white commissure
- runs medially in cord to thalamus
Tertiary neurone
- projects to lateral primary sensory cortex
Where do you get signs with a lesion in the spinothalamic tract?
Contralateral signs below lesion
As decussates at spinal level
