Pathways Flashcards
What are the major descending tracts?
- Lateral Corticospinal tract
2. Ventral Corticospinal tract
What are the major ascending tracts?
- Dorsal Columns
- Lateral Spinothalamic tract
- Ventral spinothalamic tract
What does the lateral corticospinal tract innervate?
-motor info to the Limb muscles
Where does the cell bodies in the lateral and ventral corticospinal tract?
Pre-central gyrus (primary motor cortex)
How does the axons travel in the lateral and ventral corticospinal tract?
The axons (1st order/Upper motor neurone) descend via the internal capsule, NOT the thalamus
What happens at the medulla in the corticospinal tract?
At the medulla 75-90% of the fibres decussate – these are the fibres that will form the lateral CS tract and innervate the limbs
What does the ventral corticospinal tract do?
Innervare axial (NOT desiccate)
What is the corticobulbar tract?
- Connects the motor cortex to the medullar pyramids
- Leaves the internal capsule and enters the pons
- Terminate directly on alpha motor neurones or interneurones innervating alpha motorneurons in the brainstem. These control somatic motor activity in the head e.g. muscles that control mastication, expression and eye movement
What does vestibulospinal tract?
provides info about head movement
What is the tectospinal tract?
orientation of head and neck
What is the reticulospinal tract?
breathing control and emotional motor function
Rubrospinal tract?
innervates lower motor neurones of upper limb
What does the dorsal column pathway do?
Mechanical Fine discriminative touch Pressure Vibration Proprioception
What does the spinothalamic pathway do?
Mechanical, chemical & thermal
Crude touch
Pain
Temperature
What happens when fibres enter the dorsal horn?
enter the ascending dorsal column pathways
How do the lower limb and lower trunk axons travel?
Lower limb & lower trunk axons (T6 and below) travel ipsilaterally via the medially placed gracile fasciculus (part of dorsal column)
How do the upper limb and upper trunk axons travel?
Upper limb & upper trunk axons (T5 and above) travel ipsilaterally via the laterally placed cuneate fasciculus (part of dorsal column)
Where is the the first synapse of the gracile tract?
gracile nucleus
What is the first synapse of the cuneate tract?
Cuneate nucleus
Where do second order axons decssate? (dorsal)
- in the caudal medulla to make the contralateral medial meniscus tract
- Synapse in thalamus
Where do 3rd order neurones from the thalamus project to?
- the somatosensory cortex
- Size of somatotopic areas is proportional to density of sensory receptors in that body region (somatosensory homunculus)
Where does pain and temperature sensations ascend?
within the lateral spinothalamic tract
Where does crude touch ascend?
within the anterior spinothalamic tract
Where do primary afferent axons terminate?
upon entering the spinal cord
Where do second order neurones decussate in the spinothalamic pathway?
immediately in the spinal cord and form the spinothalamic tract
Where do second order neurones terminate?
Thalamus
Where do the 3rd order neurones from thalamus project to?
Somatosensory cortex
