1.6 Somatosensory Pathways Flashcards
What are the three types of sensory receptors?
Interoreceptors, exteroreceptors and proprioception
Name the three ascending sensory pathways?
Anterolateral system, dorsal column and spinocerebellar
What does the antero-lateral system relay?
Relays pain, temp, crude touch, pressure, and proprioception sensation
Which tracts are part of the antero-lateral system?
Spinohypothalamic, spinoreticular, spinotectal, spinothalamic and spinomesencephalic
What does the dorsal column relay?
Fine touch and conscious proprioception
What are the dorsal columns called?
Fasciculus cuneatus and gracillis
Which senses are ipsilateral and which tract do the ascend?
Fine touch and proprioception - dorsal column
Which senses are contralateral and which tract do they ascend?
Pain, temp and crude touch - anterolateral spinothalamic tract
What is found in the lateral horn of a thoracic spinal vertebrae
nerves to the muscles of the limb, sensory relay neurone and preganglionic cell bodies of the ANS
Where do the fine touch nerves cross?
Cross over in the lower medulla - at dorsal column nuclei - then go through medial lemniscus
What causes sensory ataxia?
Demyelination of diseases of the dorsal column - such as MS
What is the gait like for someone suffering sensory ataxia?
Broad stamping action
What is Rhomberg’s sign?
Stand with feet together, arms out and eyes closed - sway - can also be a vestibule problem
What other symptoms are there?
Another symptoms is the loss at two point touch discrimination
What determines whether fibers travel in cuneate or gracilis dorsal column?
Gracillis - below the waste - below T6
Cuneate - above the waste
Where are the nuclei of the fasciculus gracilis and cuneate?
Lower medulla
Where do third order sensory neurons arise from?
Thalamus
What travels up the lateral spinothalamic tract? Is it contralateral or ipsilateral?
Pain and temperature - contralateral side
Where do the second order neurons of the lateral spinothalamic tract arise?
Dorsal horn synapse - substantia gelatinosa
Where do these decussate?
Anterior white commissure
What travels up the anterior spinothalamic tract? Is it contralateral or ipsilateral?
Crude touch and pressure
Explain the spinocerebellar pathway
Dorsal - ipsilateral - inferior peduncle
Ventral - contralateral - superior peduncle
Where the first order peripheral sensory cell bodies of the face found?
Trigeminal ganglion
Where do they decussate and synapse?
Synapse - principle nucleus of trigeminal - cross over at the pons
