Spinal Pathways

CD-ROM Case V: Spinal Cord InjuryNotes: Chapter 7, p. 53 - 61

Spinal Pathways 1: Objectives

Concepts:1. Review: the general anatomical and functional regions within

the gray and white matters of the spinal cord.

2. Conceptualize the arrangement of nucleus groups in the graymatter.

3 a. Identify the major ascending and descending pathways.b. Conceptualize the somatotopic organization of the pathways.

Descending Pathways:3. Trace the pathway of the corticospinal/pyramidal tracts.

Objective 1: Anatomical & Function Regions

CD-ROM, Introduction to Nervous System, Spinal Cord, frame 3-4, 23-24Notes: p. 53, Sections 7.1.1 – 7.1.2

Objective 2: Arrangement of Gray Matter

Notes: p. 53, Fig. 7-1 FYI Only

Objective 3a: Major Ascending & Descending Tracts

Notes: p. 55, Sections, Fig.7-3

Major ascending pathway:

• dorsal column / lemniscal pathway• spinothalamic tract• dorsal spinocerebellar tract • ventral spinocerebellar tract• spinoreticular tract

Major descending pathways:

• corticospinal tract (lateral and anterior)• vestibulospinal tract • descending autonomic tract• tectospinal tract• reticulospinal tract

FYI Only

Objective 3b: Somatotopic organization of the tracts

Notes: p. 54, Fig. 7-2

Sacral

Objective 4-1: Lateral Corticospinal /Pyramidal Tract

Case V, Frame 4 Notes: p. 56-57, Sections 7.4.1, Fig. 7-4

Upper motor neuron from L.L., Trunk, and U.L areas of the motor cortex descends in the pyramidal tract

Corona radiata and internal capsule

Through:

Crus cerebri

Deep to the pontine n. and pontocerebellar tract

Pyramid

Crosses to the contralateral side at the decussation of the pyramid

Then:

Descends as lateral corticospinal tract in the lateral funiculus

Enters ventral horn, and

Objective 4-2: Ant. (Ventral) Corticospinal /Pyramidal Tracts

Case V, Frame 5 Notes: p. 56-57, Sections 7.4.2, Fig. 7-4

Upper motor neuron from Trunk area of the motor cortex descends in the pyramidal tract

Corona radiata and internal capsule

Through:

Crus cerebri

Deep to the pontine n. and pontocerebellar tract

Pyramid

Ventral funiculus of the spinal cord

Then:

At the level of exit, crosses to contralateral side of the spinal cord via the ant. white commissure and enters ventral horn.Synapses with alpha motor neuron (lower motor neuron) which then exits via ventral root to innervate deep muscles in the back in the cervical and upper thoracic levels.

Review: Corticobulbar Tract

Case V, Frame 6 (Frame 6 typo: …except CN I, II, VIII)Notes: p. 56-57, Sections 7.4.3

Summary: Spinal Pathways 1 - Introduction and Descending Pathways

1. Concepts: Organization of the gray and white matter.

2. Laminae of the gray matter.

3. Somatotopic representation of the tracts.

4. Corticospinal tracts: Lateral (90%, crosses at caudal pyramid) & anterior (10%, crosses at level of exit).

Spinal Pathways 2: Objectives

Ascending Pathways:4. Trace the dorsal column/lemniscal pathway.5. Trace the pathway of the spinothalamic tract.6. Trace the pathway of the dorsal spinocerebellar tract.

Spinal cord lesions:7. Examine the effects of lesions in the spinal cord.

Objective 3b: Somatotopic organization of the tracts

Notes: p. 54, Fig. 7-2

Sacral

Objective 4: Dorsal Column/Lemniscal tracts

Case V, Frame 9 - 12Notes: p. 58-59, Fig. 7-5

Upon reaching caudal medulla, axons of the f. gracilis and f. cuneatus synapse with 2nd order neurons in n. gracilis and n. cuneatus respectively.

1st order neuron from thoracic and cervical levelsenter dorsal horn, and ascend in f. cuneatus

1st order neuron from sacral and lumbar levelsenter dorsal horn, and ascend in f. gracilis

Axons of the 2nd order neurons immediately decussate to contralateral caudal medulla and ascends in medial lemniscus

M

Medial lemniscus

Upon reaching VP nucleus of the thalamus, axons in the Medial lemnisus synapse with 3rd order neurons which travel to respective areas of sensory cortex

Objective 4: Somatotopic Representation of Dorsal Column/Lemniscal tracts

FG: Fasciculus Gracilis

FC: Fasciculus Cuneatus

NG: Fasciculus GracilisNC: Fasciculus Cuneatus

Trigeminal Nucleus

Objective 5: Spinothalamic tractCase V, Frame 13Notes: p. 60-61, Fig. 7-6

1st order neuron entersenter dorsal horn, and synapses with 2nd order neuron

2nd order neurons immediately decussate to lateral funiculus and

ascend as spinothalamic tract

2nd order neurons ascend through the brain stem

Upon reaching VP nucleus of the thalamus, axons of spinothalamic tract synapse with 3rd order neurons which travel to respective areas of sensory cortex

Objective 5: Somatotopic Representation of the Spinothalamic Tract

Spinothalamic Tract

Objective 6: Dorsal Spinocerebellar tractCase V, Frame 14 (FYI: 15)Notes: p. 60-61, Fig. 7-7

1st order neuron entersenter dorsal horn, and synapses with 2nd order neuron.

Axons of 2nd order neurons immediately enter lateral funiculus

on the ipsilateral side and ascend to brain stem

Upon reaching rostral medulla, 2nd order neuron enters cerebellum via

inferior cerebellar peduncle

Objective 7-1: Spinal Cord Lesion – Ascending and Descending Tracts

Case V, Frame 7, 16; Case Description and Discussion Notes: p. 60

Objective 7-2: Syringomyelia

Case V, Frame 17Notes: p. 60

• Occurs mostly in the cervical area of the spinal canal.

• Results in bilateral loss of sensitivity to pain and temperature because of obliteration of spinothalamic tract decussating in the white commissure.

Objective 7-3: Arterial supply of the Spinal Cord

Case V, Frame 18 TYPO in Frame 18: Radiculospinal artery,Notes: p. 60 not radicular artery

Spinal Pathways: Summary

4. Dorsal column/lemniscal tract: (x medulla oblongata)

5. Spinothalamic tract: (x level of entry)

6. Dorsal spinocerebellar tract: (no x)

7. Lesions

Limbic System

CD-ROM Case VII: A Confused AlcoholicNotes: p. 62-63

Objectives:

1a. Identify the cortical components of the limbic system.

1b. Identify the subcortical components of the limbic system

2. Describe a general pathway of the Circuit of Papez.

Cingulate Gyrus

(Mamillary Body)

Uncus/Amyglada

Parahippcampal Gyrus

Hippocampal Formation

Fornix

Objective 1a: Cortical Limbic Structures

Cerebral Cortex

• Septal area• N. accumbens• Basal Forebrain

TH

Mamillary Body

(Fornix)

Objective 1b. Subcortical Limbic Structures

Reticular Formation

Cingulate

Parahippocampal

Prefrontal

Association

VisualAssociation

Cortical:NeocortexMesocortexArchiocortex

Subcortical:Diencephalon

Brain Stem

Hippo. F.

Hippocampal Formation Fornix (axonal tract)Amygdala (?)

AF

F

F

T

HT

MB: Mamillary BodyTH: HypothalamusT: Ant. Thalamic N.

MB

Reticular FormationAutonomic & Locomotive Ctr.

BS

CircuitOfPapez

RecentlyDescribedCircuits

Notes:p. 63,Fig. 8-1