2 - Ascending & Descending Pathways Flashcards
how many neurones do ascending pathways have?
3
* primary - same side as sensatin
* secondary - decussates
* tertiary - within the brain
what 3 ascending tracts are responsible for conscious sensation/
spinothalamic
spinal reticular
dorsal column
what is the role of the spinothalamic tract?
anterior - crude touch and pressure
lateral - pain and temperature sensation
describe the route of each neuron in the spinothalamic tract:
first order - peripheral receptors to dorsal horn
secondary - decussates to other side of spinal cord and travels to thalamus
thrid order - thalamus to somatosensory cortex through internal capsule
what is the role of the spinalreticular tract?
automatic response to pain
what is the role of the dorsal column pathway?
fien tough, two touch discrimination, vibration, proprioception
where does the spinothalamic tract decussate?
spinal cord
where does the dorsal column pathway synsapse?
medulla
describe the routes of the neurones in the dorsal column:
- first order - travel through fasciculus cuneatus or fasciculus gracilis
- second order - synapses in medulla and travels to thalamus via medial lemniscus
- third order - to somatosensory cortex
what is the role of the fasciculus cuneatus?
carries upper limb info (T6 and above)
what is the role of the fasciculus gracilis?
carries infor from the lower limb (below T6)
what ascending pathways are responsible for unconscious perception?
dorsal spinocerebellar
anterior spinocerebellar
cuneocerebellar
what is the role of the dorsal spinocerebellar tract?
transmits proprioceptive info from lower limbs to cerebellum
what is the role of the ventral spinocerebellar tract?
transmits proprioceptive info from lower limbs to cerebellum
what is the role of the cuneocerebellar tract?
transmits proprioceptive info from upper limb and neck
describe the route of the neurones in the dorsal spinocerebellar tract
- 1st synapses onto second in dorsal horn
- second travels to cerebellum
- completely ipsilateral
describe the route of the neurones in the ventral spinocerebellar tract
- ipsilateral but decussates twice
- decussates on entry to spinal cord and in white matter of cerebellum
lesions in the spinothalmic tract result in what?
loss of contralateral:
* crude touch
* pressure
* pain
* temp
lesions in the dorsal column pathway result in what?
loss of ipsilateral:
* proprioception
* vibration
* fine touch
spinocerebellar lesions lead to what?
loss of ipsilateral coordination
what are the two pyramidal descending pathways?
- corticospinal tract
- corticobulbar tract
what is the corticospinal tract responsible for?
muscle control of the body
describe the route of neurones in the corticospinal tract:
- cell bodies in cerebral cortex
- pass through internal capsule
- pass through crus cerebri
- pass through pons
- at pyramids of medulla 75% fibres decussate (lateral) and synapse with LMN in ventral horn
- 25% do not decussate (anterior) - later decussate at cervical and thoracic levels
where does the corticospinal tract decussate?
75% - pyramids of medulla
25% - cervical and thoracic levels
what is the role of teh corticobulbar tract?
voluntary control of face, head and neck
what is the route of the neurones in the corticobulbar tract?
- originate in cerebral cortex
- pass through intenral capsule
- do not descend into spinal cord but synapse onto cranial nerve nuclei
the neurones of the corticobulbar tract innervate how?
bilaterally
* provide motor sensation to both sides of face
what are the 4 extrapyrimidal descending tracts?
- rubrospinal tract
- reticulospinal tract
- vestibulospinal tract
- tectospinal tract
what is the role of the rubrospinal tract?
motor control
where does the rubrospinal tract originate?
red nucleus
what is the role of the reticulospinal tract?
- medial - facilitates contraction and increases tone
- lateral - inhibits contraction
where does the reticulospinal tract originate?
medial - pons
lateral - medulla
where does the vestibulospinal tract originate?
vstibular nuclei
what is the role of the vestibulospinal tract?
balance and posture
where does the tectospinal tract originate?
superior colliculus
what is the role of the tectospinal tract?
head and eye coordination
what are signs of extrapyrimidal tract injuries?
- parkinsonisms
- chorea
- athetosis
- dystonia
how many cranial nerve nuclei are motor?
10
how many cranial nerve nuclei are sensory?
8
Label the cranial nerve nuclei
