ASCENDING PATHWAYS Flashcards
What is the simplified route for ascending pathways
Sensory information
From the periphery
Into the spinal cord through the dorsal root
Up the spinal cord
To the CNS and brain (for cerebral processing)
what paths contain first order ascending sensory neurons
fasciculus cuneatus and gracilis
what does fasiculus gracilis carry
info from lower extremities regarding touch and limb position
what does fasiculus cuneatus carry
info from upper extremities regarding touch and limb position
describe the dorsal column medial leminiscus pathway
touch, vibration, proprioception, etc info fibers enter at the dorsal roots
info is carried either on gracilis or cuneatus on first order neurons
the dorsal column fibers riding in either of those will synapse on the respective cuneatus or faciculus nuclei in the medulla
the info then ascends in the neuron pathway called medial leminiscus
ML is the 2nd order neurons and they cross midline in the middle of the medulla and ascends to the contralateral thalamus (
here they synapse on 3rd order neurons called thalamocortical projections
these projections pass through the internal capsule to go through corona radiata to get to the S1 (primary somatosensory cortex on post central gyrus)
the information going here is highly organized (think HAL)
where are the cell bodies of afferent spinal nerves?
dorsal root ganglis (pseudounipolar)
what are the first order neurons in dorsal column medial leminiscus ascending pathway
fasciculus gracilis and cuneatus pathways
which tract is lateral? (fasciculus gracilis or cuneatus?
cuneatus
which tract is medial? (fasciculus gracilis or cuneatus?
gracilis
what is the important relay portion in the ascending pathway?
thalamus
What receptors pick up info from our environment on touch, pressure, vibration and proprioception?
cutaneous
what does the Dorsal Column - Medial Lemniscus
Pathway carry
tactile and proprioceptive info (touch, pressure, vibration)
Describe the anterolateral system (lateral spinothalamic tract)
sensory - pain, temperature, crude touch (gross, big things, not fine details of touch)
contains multiple ascending paths
Describe the DC-ML Tract with sensory info from the foot
enters to the dorsal column from dorsal root ganglia
travels up the fasciculus gracilis (more medially in sc) towards the medulla
at the medulla, it will synapse at the second order neuron at the fasciculus gracilis nuclei
second order neuron crosses over at the midline of the medulla and travel up the medial leminiscal tract to the contralateral thalamus
here the second order neuron synapses with the third order neuron which then carries the sensory info in organized way to the S1, coordinating with the leg area of HAL, which would be closer to the longitudinal fissure.
what is the substantia gelatinosa
grey matter structure in dorsal spinal cord mostly involved in transmission and modulation of pain, temperature and crude touch
describe the anterolateral system (aka spinothalamic tract)
few different paths, some goes to thalamus, reticular formation, and limbic system
pain and temperature pathway
runs anterior and lateral portion of the SC
spinothalamic tract
pain pathway ascends one or two segments and then crosses over in the sc (anterior white commissure), lands in anterior lateral position of the sc and run up the rest of the way to the cortex
sends info from the thalamus to the internal capsule then to the corona radiata and to the primary somatosensory cortex
pain and temperature pathway, ride along dorsal side because it is sensory (cell body in dorsal root ganglia) and comes in the sc at the Liessauer’s tract and synapses at the substantia gelatinosa (Rexed’s lamina I & II)
describe the dorsal spinocerebellar tract
goes up to the cerebellum (known for helping with coordination)
uncrossed path that carries proprioceptive info to cerebellum so it can help us with our next movement by telling us where our muscles are that comes from the muscle spindles and golgi tendon organs
Subconscious proprioception from muscle spindles and tendon organs
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describe the ventral spinocerebellar tract
Subconscious proprioception from muscle spindles and tendon organs
similar to DSCT
going from dorsal and rides on ventral side and goes to the cerebellum
what do both the DSCT & vsct do
provide feedback to the cerebellum regarding muscle length and force so the cerebellum can coordinate the motor commands from the cortex with the feedback from the periphery to generate smooth and coordinated movements
