Ascending tracts Flashcards
What sensory pathway carries sensation of fine touch, vibration and proprioception?
Dorsal column medial lemniscus pathway
Where is the spinal cord does the dorsal column medial lemniscus pathway travel?
Dorsal columns
With regard to the dorsal column medial lemniscus pathway: Describe how sensations in the upper limb are carried by first order neurones?
- Signals from the upper limb travel in the fasciculus cunneatus part of the dorsal column (this is the lateral half)
- Synapse in the cuneate nucleus of the medullat oblongata.
With regard to the dorsal column medial lemniscus pathway: Describe how sensations in the lower limb are carried by first order neurones?
- Signals from the lower limb travel in the fasciculus gracilis (medial part of the dorsal column)
- Synapse in the gracile nucleus.
Where do the second order neurones arise from in the dorsal column medial lemniscus pathway (for upper limb)
Cuneate nucleus
Where do the second order neurones arise from in the dorsal column medial lemniscus pathway (for lower limb)
Gracile nucleus
Where is the brain stem are the cuneate and gracile nucleus?
Medulla Oblongata
Where do the second order neurones in the dorsal column medial lemniscus pathway originate and terminate?
Originate: Cuneate nucleus (upper limb) & Gracile nucleus (lower limb)
Terminate: Synapse with third order neurones in the thalamus
Do the second order neurones of the dorsal column medial lemniscus pathway decussate?
Yes. In the medulla oblongata
What area of the brain do the second order neurones in the dorsal column medial lemniscus pathway travel in to reach the thalamus? ( THINK of the name!!)
The contralateral medial lemniscus
Where do the third order neurones of the dorsal column medial lemniscus pathway originate and terminate?
Originate: Thalamus (ventral posterolateral nucleus)
Terminate: Somatosensory cortex
(Travel through the internal capsule)
Describe the tract by which sensations of fine touch, vibration and proprioception are carried from the upper limb.
These sensations will be carries in the dorsal column medial lemniscus pathway
- First order neurones receive these sensations and travel up the lateral aspect of the dorsal column of the spinal cord (fasciculus cuneatus)
- The signals are then received by second order neurones in the cuneate nucleus in the medulla oblongata.
- Second order neurones decussate at the medulla and travel in the medial lemniscus to reach the thalamus.
- From the thalamus third order neurones (ventral posterolateral nucleus) travel through the internal capsule to reach the somatosensory cortex,
Describe the tract by which sensations of fine touch, vibration and proprioception are carried from the lower limb.
- First order neurones receive sensations from the lower limb and travel in the medial aspect of the dorsal column (fasiculus gracillis)
- These are received by second order neurones in the gracile nucleus in the medulla oblongata.
- Second order neurones decussate in the medulla oblongata and travel up the contralateral medial lemniscus to reach the thalamus. (ventral posterolateral nucleus)
- Third order neurones receive the signals in the thalamus and send signals to the somatosensory cortex.
What tract carries sensations of crude touch, pain, pressure and temperature.
Spinothalamic tract
Do sensations of crude touch and pressure enter the anterior or lateral spinothalamic tract?
Anterior
Do sensations of pain and temperature enter the anterior or lateral spinothalamic tract?
Lateral
Describe the first order neurones and their function in the spinothalamic tract
- They arise from sensory receptors in the skin etc.
- They enter the spinal cord and then ascend 1 - 2 levels and terminate at the tip of the dorsal horn (substantia gelatinosa)
Describe the second order neurones and their function in the spinothalamic tract
- Synapse with the first order neurones in the substantia gelatinosa.
- Decussate to the other side of the CNS.
- Crude touch and pressure fibres enter the anterior spinothalamic tract, pain and temperature fibres enter the lateral spinothalamic tract.
- Travel to the thalamus where they synapse with third order neurones.
Describe the third order neurones and their function in the spinothalamic tract
- Recieve signals from the second order neurones in the thalamus. (in the ventral posterolateral nucleus)
- Travel through the internal capsule and terminate at the somatosensory cortex.
If there is a lesion of the dorsal colums what sensations will the patient lose and on what side of the body?
Ipsilateral loss of fine touch, vibration and proprioception
If there is a lesion of the spinothalamic tract what sensations will the patient lose and on what side of the body?
Contralateral loss of pain, temperature and crude touch sensation.
What happens when there is a complete hemisection of right side of the spinal cord (in terms of sensory pathways)
Brown sequerd syndrome
- There would be loss of fine touch, proprioception and vibration sensation on the right side of the body
- There would be loss of pain temperature and crude touch sensation on the left side.
(there will also be ipsilateral hemiparesis)
What pathway carries proprioceptive information from the lower limbs to the ipsilateral cerebellum?
Posterior spinocerebellar tract
What pathway carrier proprioceptive information from the upper limbs to the ipsilateral cerebellum?
Cuneocerebellar tract
What tract carrier proprioceptive information from the lower limbs to the ipsilateral cerebellum?
Anterior spinal cerebellar tract
What tract carrier proprioceptive information from the upper limbs to the ipsilateral cerebellum?
Rostral spinocerebellar tract
