Tracts Flashcards
What can ascending tracts be divided into
Conscious tracts
Unconscious tracts
What are the unconscious ascending tracts
Spinocerebellar tracts
What are the conscious ascending tracts
DCML
Anterolateral system
What does the DCML carry
Sensory
- fine touch (tactile sensation)
- vibration
- proprioception
Where in the spinal cord does information of the DCML travel
Dorsal (posterior) columns
Where in the brainstem is the DCML information transmitted through
Medial lemniscus
How do you remember the route of information for DCML
dorsal column
medial lemniscal
How many groups of neurones are involved in the DCML
3
first
second
third order neurones
DCML
What do first order neurones carry
Sensory information from peripheral nerves to medulla oblongata
DCML
What are the two different pathways first order neurones can take
Signals from upper limb (T6 and above)
- travel to fasciculus cuneatus (lateral part of the dorsal column)
- synapse with the nucleus cuneatus of the medulla oblongata
Signals from the lower limb (below T6)
- travel to fasciculus gracilis (medial part of the dorsal column)
- synapse in the nucleus gracilis of the medulla oblongata
DCML
What level are upper limb
T6 and above
DCML
What level are lower limb
Below T6
DCML
Where do signals from the upper limb travel
In fasciculus cuneatus - lateral part of the dorsal column
DCML
Where do signals from the lower limb travel
In fasciculus gracilis - medial part of the dorsal column
DCML
Where do signals from the upper limb synapse
Nucleus cuneatus of the medulla oblongata
DCML
Where do signals from the lower limb synapse
Nucleus gracilis of the medulla oblongata
DCML
Describe secondary order neurones
Begin in the cuneate nucleus or gracilis
Receives information from the preceding neurones - delivers it to the third order neurones in the thalamus
DCML
Where do fibres decussate
Within the medulla oblongata
Then travel in the contralateral medial lemniscus to reach the thalamus
DCML
Describe third order neurones
Transit sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
DCML
Describe the pathway of third order neurones
Ascend from the ventral posterolateral nucleus of the thalamus - travel through the internal capsule and terminate at the sensory cortex
What are the two tracts of the spinothalamic
Anterior spinothalamic
Lateral spinothalamic
Describe the anterior spinothalamic tract
Carries sensory modalities of crude touch and pressure
What does the posterior spinothalamic tract carry
Carries sensory modalities of pain and temperature
Spinothalamic
How many groups of neurones does the tract contain
3
First
Second
Third order neurones
Spinothalamic
Describe first order neurones
Arise from sensory receptors in the periphery
Enter the spinal cord - ascend 1-2 vertebral levels
Synapse at the tip of the dorsal horn
Spinothalamic
Where first order fibres synapse
1-2 vertebral levels up
Synapse at the tip of the dorsal horn - called substantia gelatinosa
Spinothalamic
Describe the route of second order neurones
Carry sensory information from the substantia gelatinosa to the thalamus
Spinothalamic
Where do fibres decussate
Within spinal cord
Spinothalamic
Second order neurones
Where do crude touch and pressure fibres enter
Anterior spinothalamic tract
Spinothalamic
Second order neurones
Where do pain and temperature fibres enter
Lateral spinothalamic tract
Spinothalamic
What can anterior and posterior spinothalamic tracts be considered
Single pathway - tracts run alongside each other
Spinothalamic
Where do second order neurones synapse
Travel superiorly within the spinal cord
Synapse in the thalamus
Spinothalamic
Describe third order neurones
Carry sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
Spinothalamic
Describe the pathway of third order neurones
Ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule and terminate at the sensory cortex
Where do corticospinal tracts begin
Cerebral cortex
What inputs do corticospinal tracts receive
Primary motor cortex
Premotor cortex
Supplementary motor area
Receive never fibres from the somatosensory area - play a role in regulating the activity of the ascending tracts
Corticospinal tract
What is the route of the neurones
Originate in the cortex
Neurones converge
Descend through the internal capsule
Pass through crus cerebri of the mid brain, pons and into medulla
most inferior (caudal) part of the medulla - tract divides into two
Describe the internal capsule
White matter pathway
Located between the thalamus and basal ganglia
Corticospinal
What does the tract divide into
Lateral corticospinal tract
Anterior corticospinal tract
Corticospinal tract
Describe the fibres within the lateral corticospinal tract
Decussate
Descend into the spinal cord
Terminate at the ventral horn (at all levels) - lower motor neurones go from here
Corticospinal tract
Describe the fibres of the anterior corticospinal tract
Remain ipsilateral
Descends into the spinal cord
Decussate and terminate in ventral horn of cervical and upper thoracic segmental levels
Corticospinal tract
Where do fibres of the lateral corticospinal tract terminate
Ventral horn of all levels
Corticospinal tract
Where do fibres of the anterior corticospinal tract terminate
Ventral horn of the cervical and upper thoracic segmental levels
Corticospinal tract
Where do fibres of the lateral corticospinal tract decussate
Most caudal of the medulla
Corticospinal tract
Where do fibres of the posterior corticospinal tract decussate
Ventral horn of the cervical and upper thoracic segmental levels
