Neuroscience: Ascending Pathways

Front 1

Dorsal Column-Medial Lemniscal Pathway

Back 1

-carry discrimitive tactile sensations from the body
-touch, pressure, 2 point discrimination, vibratory, stereognosis, conscious proprioception (position/mvmt)
-innervated by A-beta afferents
-enter SC in more medial region of Lissauer's tract

Front 2

DCML:
1) Neurons
2) Destination
3) Decussation

Back 2

1. 1st: DRG (pseudounipolar, A-beta)
2nd: Nucleus gracilus, nucleus cuneatus
3rd: Thalamic (VPL)

2. primary somatosensory cortex

3. caudal medulla: internal arcuate Fibers

Front 3

DCML Pathway Route LE

Back 3

DRG-->Dorsal Root-->fasciculus gracilis travel up SC-->medulla: nucleus gracilis-->synapse:2nd order-->cross at arcuate fibers-->thalamus (VPL): synapse 3rd order--> somatosensory cortex

Front 4

DCML Pathway Route UE

Back 4

DRG-->Dorsal Root->travel up SC fasiculus cuneatus-->medulla: nucleus cuneatus-->synapse 2nd order-->medial leniscus-->internal capsule-->somatosens cortex

Front 5

Trigeminal Lemniscal Pathway
1) Neurons
2) Destination
3) Decussation

Back 5

1. 1st: Trigeminal Ganglion
2nd: Main Sensory Nucleus of Trigeminal Nerve
3rd: Thalamic VPM

2. Primary Somatosensory Cortex

3. pons

Front 6

Trigeminal Lemniscal Pathway Route

Back 6

1st order: peripheral axon (info from face)-->trigeminal nucleus: synapse-->2nd order-->cross medial leniscus-->synapse 3rd order: ipsilateral trigeminal main sensory-->thalamocorotical projections-->corona radiata--> somatosensory cortex

Front 7

DCML Pathway Crossing vs. Trigeminal Crossing

Back 7

DCML: Cross at medulla (internal arcuate fibers)

Trigeminal: Cross at pons (medial leniscus)

Front 8

Spinothalamic Tracts (Anterolateral System)
1) Neurons
2) Destination
3) Decussation

Back 8

-sensory modalities: pain, temp, crude touch
1. 1st: DRG
2nd: Substantia gelatinosa Rexed's Lamina II in dorsal horn
3rd: Thalamus (VPL)

2. Primary Somatosensory Cortex

3. w/in 1-2 levels of entering SC at Anterior White Commisure

Front 9

Spinothalamic Tract Route

Back 9

A-delta & C afferent: 1st order--> enter lateral region of lissauer's tract-->synapse: substantia gelatinosa (2nd order)-->ascends 1-2 segments of SC-->cross midline in anterior white commissure-->thalamus: synapse on thalamic neurons-->3rd order: thalamocortical projections (corona radiata)-->primary somatosens cortex (some terminate in brainstem reticular formation=spinoreticular fibers)

Front 10

Trigeminothalamic Tract
1) Neurons
2) Destination
3) Decussation

Back 10

1. 1st: trigeminal ganglion
2nd: spinal nucleus of trigeminal nerve in medulla
3rd: Thalamus (VPM)

2. Primary Somatosensory Cortex

3. Medulla

Front 11

Trigeminothalamic Tract Route

Back 11

st order: A-delta & C afferent of trigeminal gang-->enter pons-->descend ipsilaterally-->synapse on spinal nucleus of trigeminal nerve in medulla-->2nd order:cross in medulla-->ascend in trigeminal lemniscus to contralateral thalamus VPM-->3rd order send thalamocortical projections to primary somat. cortex (corona radiata)

Front 12

What does Dorsal Spinocerebellar Tract (DSCT) & Spinocuneocerebelar Tract (SCCT) sense?

Back 12

-Sensory: subconscious proprioception from muscle spindles & tendon organs, DSCT=LE & SCCT=UE

Front 13

Dorsal (Posterior) Spinocerebellar Tract
1) Neurons
2) Destination
3) Decussation

Back 13

1. 1st: DRG
2nd: Clarks Column in dorsal horn T6 & below
3rd:

2. Cerebellum via inferior cerbellar peduncle

3. NO decussation

Front 14

Dorsal Spinocerebellar Tract Route

Back 14

IA & II (Muscle spindle-stretch) & IB (golgitendon organ-force) (dorsal)-->Clarks's nucleus: 2nd order-->ascend as cerebellar tract-->lateral finiculus-->enter cerebellum via inf. peduncle-->terminate in vermis of cerebellum-->fine coordination of posture/mvmt of limb muscle (LE)

Front 15

Spinocuneocerebellar Tract
1) Neurons
2) Destination
3) Decussation

Back 15

1. 1st: DRG (cervical)
2nd: Cuneate Nucleus (medulla)
3rd:

2. Destination: cerebellum via inf. cerbellar peduncle

3. NO decussation

Front 16

Spinocuneocerebellar Tract Route

Back 16

Group IA, II, & IB affarent 1st order-->enter dorsal horn & branch-->alpha motor neurons directly & some ascend in ipsilateral cuneate fascilus-->synapse on neurons on cuneate nucleus-->2nd order: enter cerebellum via inferior cerebellar peduncle-->fine coordination of posture/mvmt UE (smooth, coordinated mvmt)

Front 17

Ventral Spinocerebellar Tract & Rostral Spinocerebellar Tract Fxn

Back 17

Carries information to cerebellum about descending motor signals
-VSCT: thoracic & lumbar SC
-RSCT: cervical SC

internal feedback pathway monitors corticospinal & brainstem-spinal signals to SC

Front 18

VSCT:
1) Neurons
2) Destination
3) Decussation

Back 18

1. 1st: Lamina V, VI, VII
2. Bilateral cerebellum via superior cerebellar peduncle
3. Spinal Cord level- anterior white commisure

Front 19

VSCT Route

Back 19

Neurons in lamina V, VI, & VII of thoracic & lumbar SC-->cross in SC at anterior white commissure-->ascend as VSCT in lateral funiculus-->enter cerebellum via sup. cerebellar peduncle--> most cross again to end up ipsilateral, but some remain contralateral

Front 20

Rostral Spinocerebellar Tract
1) Neurons
2) Destination
3) Decussation

Back 20

1. 1st: Lamina V, VI, VII (cervical)
2. Ipsilateral cerebellum via sup/inf cerbellar peduncle
3. No decussation

Front 21

RSCT Route

Back 21

Lamina V, VI, VII-->ascend ipsilaterally in SC & Medulla-->enter cerebellum via both inf/sup cerebellar peduncles-->synapse bilaterally

Front 22

DCML Pathway Lesions

Back 22

Peripheral Region: ipsilateral loss

Spinal Region: ipsilateral loss

Lower medulla: ipsilateral loss

Cerebrum, midbrain, pons & upper medulla: Contralateral loss

Front 23

Spinothalamic Pathway Lesions

Back 23

Peripheral: ipsilateral

Spinal Region: loss pain/temp from contralat 1-2 levels below lesion

Lower pons, medulls: mixed hemianesthesia-crossed analgesia (contralat body & ipsalat. face)=trigeminal and spinothalamic axons disrupt.
trigeminal lemniscus axons=contralat loss of face

Front 24

Segmental Reflexes

Back 24

-involuntary, stereotyped response to sensory input
-receptor, afferent neuron, and efferent neuron
-most involve 1 or more interneurons (except monosynaptic stretch reflex)

Front 25

Stretch Reflex

Back 25

-knee jerk reflex, deep tendon reflex, myotatic reflex, la monosynaptic reflex
-mxn: msucle stretch activates IA & II afferent of spindle-->activate Alpha-MN-->stretch muscle
-DOESN"T inlvove tendon organs
-any pressure/damage on dosal/ventral roots reduce relflex exciteablity

Front 26

Jendrassik Maneuver

Jaw-jerk reflex

Back 26

-clasping fingers together & pulling hands apart: mediated by propriospinal (intersegmental path)

-mediated by trigeminal nerve, CN V