NS 6 - pathways - ascending Flashcards
name the two pathways to the cerebral cortex
dorsal column and the anterolateral system
describe ascending tracts
neural pathway by which sensory info from the peripheral nerves is transmitted to the cerebral cortex
which tracts are compromised of the dorsal column and the anterolateral system?
conscious tracts
which tracts are comprimised of spinocerebellar tracts?
unconscious
which sensory modalities does the dorsal column-medial lemniscal pathway carry?
fine touch, vibration and proprioception
where does the DCML pathway occur?
in spinal cord travels via dorsal columns
in the brain stem it is transmitted through medial lemniscus
first order neuron carries which sensory information (DCLM)
touch, proprioception or vibration from the peripheral nerves to medulla oblongata
where do the signals from the upper limb (T6 and above) travel?
(first order neuron)
in the fasciculus cunneatus (lateral part of dorsal column) they then synapse in the medulla
where do signals from the lower limb (below T6) travel? (first order neuron)
fasciculus gracilis (medial part of the dorsal column) they then synapse in the nucleus gracilis of the medulla oblongata
where do 2nd order neurons begin? (DCLM)
either in nucleus gracilis or cuneate
what is the main job of 2nd order neurons?
the fibres recieve info from the preceding neurons and delivers it to the 3rd order neurons in the thalamus
- within the medulla oblongata these fibres cross to the other side of the CNS, they then travel in the contralateral medial lemniscus to reach the thalamus
describe the conus medullaris?
the lower extremity of the spinal cord
describe the filum terminale
a delicate strand of fibrous tissue preceding from the apex of the conus medullaris
describe the cuada equina
bunch of spinal nerves found at the bottom third of the spinal cord
Name the two types of spinothalamic tract
anterior and lateral
what sensory modalities do the anterior spinothalamic tract carry?
crude touch and pressure
what sensory modalities does the lateral spinothalamic tract carry?
pain and temperature
dorsal column pathway - Leg details…
- First neuron leg fibres in gracile tract (Spinal Cord)
- 2nd neuron in gracile nucleus (medulla) (crosses to medial)
- 2nd neuron continues in medial lemniscus
- third neuron continues to cerebral cortex (post central gyrus
Dorsal Column - Arm details
- first neuron arm fibres in cuneate tract (spinal tract)
- second neuron in cuneate nucleus crosses midline (medulla)
- 2nd neuron continues in medial lemniscus
- third neuron continues to cerebral cortex - post central gyrus
is the anterolateral tract an ascending tract?
yes
which sensations does the anterolateral tract provide?
coarse touch, localised pain, temperature, itch
where are the anterolateral tracts located?
white matter
describe the anterolateraltract in terms of neurons
- finger touches hot water
- 1st neuron in spinal cord
- 2nd neuron posterior horn (crosses to opposite side close to same level in white commissure ascends to thalamus)
- third neuron synapses in thalamus and then projects to cerebral cortex
name the two types of pain?
Discriminative ‘‘localising pain’’ and affective ‘‘suffering pain’’
describe affective pain and its fibres
less localised and longer lasting via unmyelinated C fibres
Describe discriminative pain
well localised and brief via A delta fibres (small myelinated fibres)
which tract does the discriminative pathway follow?
anterolateral (neospinothalamic)
anterolateral tract –> thalamus (VPL) nucleus –> post central gyrus
which tract does the affective pain pathway follow?
spinoreticular (paleospinothalamic)
bilateral –> reticular formation (brain stem) –> thalamus (intralaminar nucleus) –> also connnects to hypothalamus and amygdala (deep in temporal lobe) –> cingulate gyrus
which cortical areas are involved in pain perception?
- post central gyrus (discriminitive)
- insula (both)
cingulate gyrus (affective pain)
what treats pain and reduces fMRI signals in insula and thalamus?
opioid
in which tracts does the 2nd neuron cross in the spinal cord?
anterolateral (spinothalamic) tract
in the dorsal column does the second neuron cross in the spinal cord?
nope
a hemisection of the cord would result in?
loss of pain sensation on contralateral below lesion and loss of proprioception ipsilaterally below
pathways to the cerebellum (ascending)
dorsal and ventral spinocerebellar tracts
2 neurons same side
dorsal spinocerebellar tracts
unconscious proprioception muscle spindles/ tendon organs mainly from leg same side
from leg –> from arm clarkes nucleus (same side) –> lateral cuneate nucleus
inferior C. peduncle - same side - cerebellar entry
ventral spinocerebellar tracts
also mainly concerned with leg input - movement
superior cerebellar peduncle
