Sensory Pathways 2 Flashcards
Which type of fibres does the neo-spinothalamic tract transmit?
A delta
Which type of fibres does the paleo-spinothalamic tract transmit?
C fibres
Where do second order neurones of the neospinothalamic tract synapse?
Ventral posterolateral nucleus (VPL) of the thalamus
Where do second order neurones of the paleospinothalamic tract synapse?
Intralaminar and dorsomedial nuclei of the thalamus
What type of information does the neospinothalamic pathway carry?
Fast, sharp pain
What type of information does the paleospinothalamic pathway carry?
Slow, dull pain
Why is the neo pathways referred to as discriminating and the paleo referred to as undiscriminating?
VPL has somatotopic map so gives locational discrimination
DM and intralaminar areas only provide generalised location for pain
What is the role of the spinoreticular pathway?
Motor response and ascending arousal
What is the role of the spinomesencephalic pathway?
Descending pain modulation
Which rexed laminae do the spinothalamic and spinomesencephalic tracts originate from?
1 and 5
Which rexed laminae does the spinoreticular tract originate from?
6-8 (intermediate zone)
What is the overall function of the spinothalamic tracts?
Pain basis for avoidance behaviours that protect us from harm
What is said to be one of the hardest pains to bear?
Prolonged stimulation of the paleo-spinothalamic pathway
Why does pain prevent sleep?
Spinothalamic tracts synapse with brainstem nuclei to increase arousal
Why does pain make you sweat and feel nauseous?
Spinothalamic tracts indirectly stimulate autonomic circuitry
Why is there an emotional component of pain?
Spinothalamic tracts positively associated with the limbic system
How would a lesion to the neospinothalamic pathway present?
Decreased perception of pain and temperature on the contralateral side of the body, always one or two dermatomes below the level of the lesion (Lissauers tract)
What is a cordotomy?
Surgical procedure where anterolateral portion of cord is lesioned using electrical current used in terminal disease pain
How are paraesthesias associated with the spinothalamic tract felt?
Searing, shooting or burning pain
What is the function of the mesencephalic nucleus?
Proprioception from mouth/jaw
What is the function of the sensory nucleus?
Discriminating tough, vibration and conscious proprioception from the face
What is the function of the spinal nucleus?
Pain and temperature sensation from face, back of tongue, pharynx, larynx and ear
Where do neurones from the sensory nucleus project to?
VPM of thalamus
What information is carried in the trigeminal lemniscus from the sensory nucleus?
Touch and sensation from the face
What information is carried in the posterior trigeminothalamic tract from the sensory nucleus?
Touch and vibration from the mouth
Where does the trigeminal lemniscus project to from the VPM?
Somatosensory cortex
Which side of the spinal cord do the trigeminal lemniscus and posterior trigeminothalamic tracts travel from the sensory nucleus?
Posterior trigeminothalamic - ipsilateral
Trigeminal lemniscus - contralateral
Where do C and A delta fibres enter the spinal cord from the spinal nucleus?
Mid pontine level
Where is the spinal trigeminal nucleus?
C1
Where do C and A delta fibres travel when they enter the spinal cord?
Down the cord to spinal nucleus in spinal trigeminal tract
What is the path taken by 2nd order neurons from the spinal nucleus?
Cross midline and ascend contralaterally in trigeminal lemniscus
Give off trigeminoreticular and trigeminomesencephalic tracts
Where do 2nd order neurons from the spinal nucleus synapse?
VPM of thalamus
What are the symptoms of trigeminal neuralgia?
Intense shotting sharp pain in areas innervated by the trigeminal nerve often in response to light tough
What is thought to cause trigeminal neuralgia?
quasi-ectopic firing of nerve induced by normally low frequency APs
What disease is trigeminal neuralgia associated with?
Demyelinating disorders such as MS
What is trigeminal neuralgia treated with?
Voltage sensitive sodium channel blockers e.g. phenytoin
What information enters the posterior spinocerebellar pathway?
LL proprioception
What information enters the cuneocerebellar pathway?
UL proprioception
Where do axons carrying proprioception from the lower limb synapse?
Clarke’s nucleus
Where do axons carrying proprioception from the upper limb synapse?
Accessory cuneate nucleus
Where do the posterior spinocerebellar and cuneocerebellar pathways enter the cerebellum?
Inferior peduncle
Where do axons from the limbs in the integrated pathway synapse?
Spinal border cells
What 3 pathways synapse on spinal border cells?
Descending modulation
Reflex arcs
Limb proprioception
Describe the path taken by neurons in the anterior spinocerebellar from the spinal border cells
Cross midline and ascend contralaterally
Enter cerebellum at contralateral superior peduncle then recross
==> ipsilateral
Describe the path taken by neurons in the rostral spinocerebellar from the spinal border cells
Ascend ipsilaterally
Enter cerebellum via the superior and inferior peduncles
What information is carried in the rostral spinocerebellar pathway?
Integrated UL proprioception
What information is carried in the anterior spinocerebellar pathway?
Integrated LL proprioception
Name the 2 integrated cerebellar pathways
Anterior and rostrals spinocerebellar
Name the 2 unintegrated cerebellar pathways
Cuneocerebellar
Posterior spinocerebellar
Which protein is affected in Friedreich’s ataxia?
Frataxin (multiple repeats of gene)
What are the clinical features of Friedreich’s ataxia?
Progressively uncoordinated limbs
Wide based ‘reeling’ gait
Intention tremor
