ASCENDING PATHWAYS

Question 1

What is the simplified route for ascending pathways

Answer 1

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)

Question 2

what paths contain first order ascending sensory neurons

Answer 2

fasciculus cuneatus and gracilis

Question 3

what does fasiculus gracilis carry

Answer 3

info from lower extremities regarding touch and limb position

Question 4

what does fasiculus cuneatus carry

Answer 4

info from upper extremities regarding touch and limb position

Question 5

describe the dorsal column medial leminiscus pathway

Answer 5

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)

Question 6

where are the cell bodies of afferent spinal nerves?

Answer 6

dorsal root ganglis (pseudounipolar)

Question 7

what are the first order neurons in dorsal column medial leminiscus ascending pathway

Answer 7

fasciculus gracilis and cuneatus pathways

Question 8

which tract is lateral? (fasciculus gracilis or cuneatus?

Answer 8

cuneatus

Question 9

which tract is medial? (fasciculus gracilis or cuneatus?

Answer 9

gracilis

Question 10

what is the important relay portion in the ascending pathway?

Answer 10

thalamus

Question 11

What receptors pick up info from our environment on touch, pressure, vibration and proprioception?

Answer 11

cutaneous

Question 12

what does the Dorsal Column - Medial Lemniscus
Pathway carry

Answer 12

tactile and proprioceptive info (touch, pressure, vibration)

Question 13

Describe the anterolateral system (lateral spinothalamic tract)

Answer 13

sensory - pain, temperature, crude touch (gross, big things, not fine details of touch)
contains multiple ascending paths

Question 14

Describe the DC-ML Tract with sensory info from the foot

Answer 14

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.

Question 15

what is the substantia gelatinosa

Answer 15

grey matter structure in dorsal spinal cord mostly involved in transmission and modulation of pain, temperature and crude touch

Question 16

describe the anterolateral system (aka spinothalamic tract)

Answer 16

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)

Question 17

describe the dorsal spinocerebellar tract

Answer 17

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
`

Question 18

describe the ventral spinocerebellar tract

Answer 18

Subconscious proprioception from muscle spindles and tendon organs
similar to DSCT
going from dorsal and rides on ventral side and goes to the cerebellum

Question 19

what do both the DSCT & vsct do

Answer 19

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