Ascending tracts Flashcards
Name the conscious ascending tracts
Anterolateral Spinothalamic
Dorsal column
Name the unconscious ascending tracts
Spinocerebellar
What are the modalities of the Dorsal tract?
Conscious proprioception
Fine touch
What are the modalities of the Anterolateral Spinothalamic tracts?
Crude touch
Pain
Temperature
Pressure
What are the modalities of the Spinocerebellar tracts?
Unconscious proprioception
Which part of the Dorsal column do signals from the upper limb travel in?
Fasciculus cuneatus (Outer part of tract)
Which part of the Dorsal column do signals from the lower limb travel in?
Fasciculus gracilis (Inner part of tract)
Where do first order neurones of the fasciculus cuneatus synapse?
In the cuneate nucleus of the medulla
Where do first order neurones of the fasciculus gracilis synapse?
In the gracile nucleus of the medulla
What is the route of second order neurones in the dorsal tracts?
Leave nucleus in medulla
Decussate in medulla oblongata
Insert on contralateral side of the Thalamus
What is the route of third order neurones in the dorsal tracts?
Leave VPL nucleus of thalamus
Enter somatosensory cortex
Briefly, what is the route of the Dorsal tract?
Enter spinal cord with cell body in Dorsal root ganglion
Stay on ipsilateral side and travel up to nucleus in medulla
Synapse and decussate in medulla oblongata
Travel up to contralateral side of thalamus
Synapse and leave VPL nucleus of thalamus to go to somatosensory cortex
What is the route of the first order neurones in the Anterolateral spinothalamic tracts?
Arise at receptors and rise 1-2 levels then synapse in the dorsal horn (substantia gelatinosa)
What is the route of the second order neurons in the Anterolateral spinothalamic tracts?
Leave substantia gelatinosa and decussate
Split into anterior and lateral columns and ascend in the contralateral side of the spinal cord (Still run alongside each other)
Synapse in contralateral side of the thalamus
What is the route of the third order neurones in the Anterolateral spinothalamic tracts?
Leave VPL nucleus in thalamus and go to somatosensory cortex
How many neurones are in the spinocerebellar tract?
Two - There is no third order neurone as it does not go to the cortex!
Where do the first order neurones of the spinocerebellar tract synpase?
Dependent on which fibres of the tract;
- Neurones that remain ipsilateral synapse in Clarke’s nucleus
- Neurones that decussate synapse in the Dorsal horn
What do some fibres of the spinocerebellar tracts do?
Decussate twice - once just below the cerebellum (Superior cerebellar peduncle) and then again in the cerebellum
All fibres of the spinocerebellar tract insert into the cerebellum on the ipsilateral side. True/False?
True
Some remain ipsilateral the whole time, other decussate but then decussate again so end up ipsilateral.
What can cause a lesion in the spinal cord of the Dorsal column tract?
Vitamin B12 deficiency Tabes Dorsalis (Neurological issue seen in late stage syphillis)
What pattern of sensory loss will be seen with a lesion in the spinal cord of the Dorsal column tract?
Ipsilateral loss of conscious proprioception and fine touch (As decussation in medulla oblongata)
What is the pattern of sensory loss if damage to the Anterolateral Spinothalamic tract occurs?
Contralateral loss of pain and temperature as well as crude touch and pressure (As decussate in the spinal cord)
What is the injury in Brown-Séquard syndrome?
Hemisection of the spinal cord (One sided lesion) affecting the Dorsal column tract and the Anterolateral Spinothalamic tract. Most often due to trauma
What is the pattern of sensory loss in Brown-Séquard syndrome?
Ipsilateral loss of fine touch and conscious proprioception (As dorsal column tract damaged)
Contralateral loss of pain and temperature (As Anterolateral Spinothalamic tract damaged)
Will also have damage to the descending tracts causing ipsilateral hemiparesis
What is the defect when damage to the Spinocerebellar tract occurs?
Ipsilateral loss of muscle co-ordination (due to loss of unconscious proprioception)
Rarely occurs in isolation, usually involes the descending tracts so may have muscle weakness/paralysis
