W4 - Spinal Cord Tracts (Asc + Desc) Flashcards
What are the three ascending tracts called?
DCML pathway, spinothalamic and spinocerebellar tract
The dorsal column carries the two DCML pathways, the fasciculus gracilis and cuneatus, what two types of information are carried here?
Conscious proprioception and discriminative touch
What three bits of information are carries in the spinothalamic tract?
Innocuous temp, pain and crude touch
What 3 bits of info do the two spinocerebellar tracts carry? (dorsal and ventral)
Movement coord, unconscious proprioception and other cutaneous sensory info
Describe the 3 step/neuron pathway of the DCML pathways (part 1)
FC or FG mechanoreceptor sensory afferent from arm/leg respectively ascend through dorsal horn, this synapses in the medulla to the medial lemniscus neuron
Describe the 3 step/neuron pathway of the DCML pathways (part 2)
The medial lemniscus neuron decussates and ascends to synapse with the VPL neuron in the nucleus of the thalamus
Describe the 3 step/neuron pathway of the DCML pathways (part 3)
The VPL projects to the primary somatosensory cortex
Are the diameters of the afferents in the DCML and spinothalamic pathways small or large?
DCML - large, STT - small
Describe the 3 step/neuron pathway of the STT pathway (part 1)
Primary afferent goes into the lamina 1 and 5 of the grey matter in the SC, synapsing with a second order neuron
Describe the 3 step/neuron pathway of the STT pathways (part 2)
The second order neuron decussates and ascends in either the dorsal or ventral STT, synapsing with a 3rd order neuron in the thalamus
Describe the 3 step/neuron pathway of the STT pathways (part 3)
3rd order VPL neuron projects to somatosensory cortex
Are ascending or descending tracts sensory/motor?
Ascending sensory and descending motor
List the 4 descending tracts
Reticulospinal, vestibulospinal, rubrospinal and corticospinal
Which descending tract directs coluntary movement, reflexes and muscle tone via alpha and gamma motor neurons?
Reticulospinal
What are the only nervous fibres associated with the ANS?
B
Which descending tract controls posture and reflexes of head, eye, neck when the body moves?
Vestibulospinal
The rubrospinal tract originates in the midbrain red nucleus, what does it control?
Limb flexor muscles of upper limbs in humans
The corticospinal tract originates in the motor cortex, what does it control?
Discrete, skilled movements of distal limbs
What is the corticospinal tract the principle pathway of in humans?
Motor control
Step 1 of corticospinal tract
Cortical axons travel via posterior limb of the internal capsule through the ventral brainstem
Step 2 of corticospinal tract
Most fibres decussate at the junction between medulla and SC
Step 3 of corticospinal tract
Cortical axons continue to descend through the lateral column and synapses in ventral horn to motor/interneurons
