ascending and descending tracts Flashcards
what is the end of the spinal cord (yellow part) called
conus medullaris
what does the conus medullaris continue into
filum terminalis (connective tissue) which is anchored to the dorsum of coccyx
what are the three layers of meninges around spinal cord
-dura
-arachnoid
-pia
where is the lateral horn present
T1-L2,L3
(where you get preganglionic sympathetic fibres)
what are these
lamina of rexed
arteries of the spinal cord
what is the space in between the dura and the bone in the spinal canal called
epidural space
describe dorsal column-medial lemniscus pathway
- First order neurones carry sensory information from peripheral nerves to the medulla oblongata
- Within the medulla oblongata these fibres decussate (cross to the other side of the CNS); they then travel in the contralateral medial lemniscus to reach the thalamus
- The third order neurones transmit the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
is the dorsal column-medial lemniscal pathway a conscious or unconscious tract
conscious
what does the anterior spinothalamic tract do
carries the sensory modalities of crude touch and pressure
what does the lateral spinothalamic tract do
carries the sensory modalities of pain and temperature
first order neurons in spinothalamic tract
-they arise from the sensory receptors in the periphery
-They enter the spinal cord, ascend 1-2 vertebral levels, and synapse at the tip of the dorsal horn (the substantia gelatinosa)
second order neurons in the spinothalamic tract
-they carry the sensory information from the substantia gelatinosa to the thalamus
-After synapsing with the first order neurones, these fibres decussate within the spinal cord (cross segmentally), and then form two distinct tracts (AST and LST)
third order neurons in spinothalamic tract
carry the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
what is pyramidal tract responsible for
fine, precise movement particularly of lower limb muscles
tectospinal tract
- Input mostly to cervical segments
- Thought to mediate head and neck movement due to visual stimuli
reticulospinal tract function
- Has many nuclei and receives input from virtually all parts of the CNS
- It has many functions, including the influencing of voluntary movement
where does medial reticulospinal tract arise from
the pons
where does lateral reticulospinal tract arise from
medulla
is the anterolateral system a conscious or unconscious tract
conscious
in the DCML, where do first order neurons travel with signals from the upper limb
travel in fasciculus cuneatus (lateral part of the dorsal column) then they synapse in the nucleus cutaneous of the medulla oblongata
In the DCML, where do first order neurons with signals from the lower limb travel
they travel in the fasciculus gracilis (medial part of the dorsal column), then they synapse in the nucleus gracilis of the medulla oblongata
where do second order neurons begin in the DCML
in the cuneate nucleus or gracilis
what are the two tracts in the anterolateral system
-anterior spinothlamic tract
-lateral spinothalamic tract
what info does the anterior spinothalamic tract carry
sensory modalities of crude touch and pressure
what info does the lateral spinothalamic tract carry
sensory modalities of pain and temperature
what do first order neurons in the anterolateral system do
-arise from the sensory receptors in the periphery
-enter the spinal cord
-ascend 1-2 vertebral levels
-synapse at the tip of the dorsal horn (substantia gelatinosa)
what do second order neurons in the anterolateral system do
-carry sensory info from the substantia gelatinosa to the thalamus
-fibres decussate within the spinal cord and then form the anterior and the lateral tract
-these tracts then synapse within the thalamus
what do third order neurons in the anterolateral system do
carry the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
what are the descending tracts
pathways by which motor signals are sent from the brain to the lower motor neurons
what is the corticospinal tract responsible for (pyramidal tract)
fine, precise movement
-particularly of distal limb muscles
what are the pyramids
tracts form visible ridges on the anterior surface of the medulla called pyramids
where do most fibres of the corticospinal tract cross when they decussate
caudal medulla
name the extra-pyramidal tracts
-tectospinal tract
-reticulospinal tract
-vestibulospinal tract
vestibulospinal tract
excitatory input to antigravity extensor muscles
where does vestibulospinal tract originate from
fibres originate in the vestibular nuclei of the pons and medulla
