1. The Nervous System ——The Spinal Cord
Liu jiao
Binzhou Medical University
Department Of Anatomy

2. Divisions
Central nervous system (CNS)
Peripheral nervous system (PNS)

3. Central nervous system (CNS)
Brain
Telencephalon
Diencephalon
Cerebellum
Brain stem
Midbrain
Pons
Medulla oblongata
Spinal cord

4. Reflex and reflex arc
Reflex: a reaction of the organism by the nervous system in response to a stimulus
Reflex arc: has 5 basic components
Receptor ↓
Sensory neurons
CNS
Moter neurons
Effector

5. The Spinal Cord 脊髓 Position It is located in the vertebral canal
Continuous above with medulla oblongata at level of foramen magnum
Ends below at lower border of L1 in adult; at birth at level of L3

6. External features
A long cylindrical structure and slightly flattened anteroposteriorly,
Conus medullaris（conical termination）
Filum terminale （formed by a condensation of pia mater）
Cauda equina
Diameters of the spinal cord are not equal at various level.
Two enlargements
Cervical enlargement : corresponds to the C4 to the T1 segments
Lumbosacral enlargement : corresponds to the L2 to the S3 segments

7. Fissure and sulci Anterior median fissure Posterior median sulcus
Anterolateral sulcus－anterior (motor) roots emerge serially
Posterolateral sulcus－posterior (sensory) roots enter spinal cord, each bear a spinal ganglion which constitutes the first cell-station of the sensory nerves

8. Relationship of segments of spinal cord to vertebrae
A portion of the cord that gives rise to a pair of spinal nerve constitutes a segment.
There are 31 segments
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

9. Relationship of segments of spinal cord to vertebrae
Spinal segments
Vertebral levels (spines)
Upper cervical region (C1~C4)
= C1 ~ C4
Lower cervical and upper thoracic region (C5~T4)
— 1 = C4 ~ T3
Middle thoracic region (T5~T8)
— 2 = T3 ~ T6
Lower thoracic region (T9~T12)
— 3 = T6 ~ T9
Lumber segments
= T10 ~ T12
Sacral and coccygeal segments
= L1

10. Internal structures Central canal Gray matter Lateral horn (column)
Anterior horn (column)
Posterior horn (column)
Intermediate zone
Lateral horn (column)
Anterior gray commissures Posterior gray commissures White matter
Anterior funiculus
lateral funiculus
Posterior funiculus
Anterior white commisure

11. Posterior horn (column):
Marginal layer
Substantia gelatinosa
Nucleus proprius
Nucleus thoracicus
in segments C8~L3

12. Intermediate zone
Intermediaolateral nucleus (lateral horn or column): lies in segments T1~L3, containing sympathetic preganglionic neurons
Sacral parasympathetic nucleus: lies in segments S2~S4, containing parasympathetic preganglionic neurons
Intermediomedial nucleus : for sensation of viscera

13. Anterior horn (column): contain motor neurons
Three kinds of neuron
α-motor neuron: larger multipolar neuron, innervates extrafusal fibers of skeletal m., producing contraction of m.
γ-motor neuron: smaller neuron, innervates intrafusal fibers regulating muscular tonus
Renshaw’s cell: negative feedback mechanism
Two groups of nuclei
Medial nuclear group: present in most segments of spinal cord, innervating axial muscles
Lateral nuclear group: present only in cervical and lumbosacral enlargements, innervating limb muscles

14. Rexed’s lamina 板层 posterior horn is formed by lamina Ⅰ to Ⅵ；
Intermediate zone corresponding to lamina Ⅶ；
Anterior horn is composed laminae Ⅷ and Ⅸ；
lamina Ⅹ is the gray matter surrounding the central canal.

15. Important Subdivision of Spinal Cord Gray Matter
Region
Lamina
Nucleus
Posterior horn Ⅰ
Marginal layer Ⅱ
Substantia gelatinosa
Ⅲ, Ⅳ
Nucleus proprius
Intermediate zone Ⅶ
Nucleus thoracicus (C8~L3)
Intermediolateral nucleus (T1~L3)
Sacral parasympathetic nucleus (S2~S4)
Intermediomedial nucleus
Anterior horn Ⅸ
Motor neuron

16. Ⅲ) White matter
White matter contains three kinds of fibers: ascending, descending, and fasciculus proprius

17. Ascending tracts Fasciculus gracilis Fasciculus cuneatus
Posterior spinocerebellar tract
Anterior spinocerebellar tract
Spinothalamic tract

18. Fasciculus gracilis and fasciculus cuneatus
Fasciculus gracilis and fasciculus cuneatus enter the ipislateral posterior funiculus of the spinal cord
The fiber arising from sacral, lumbar and lower 8 thoracic segements make up the fasciculus gracilis.
While the fiber arising from the upper 4 thoracic and cervical segements make up the fasciculus cuneatus.
The two tracts conduct impuls of the discriminating tactle (ability to recognize the size, shape, and texture of an object) and kinesthetic (sense of position, movement and vibration) T3 T4 T5
Spinal ganglion T6

20. Ascending tracts Spinothalamic tract 脊神经节
It includes lateral and anterior spinothalamic tracts, and its fibers associated with pain and thermal senses.
The fibers cross in the anterior commissure and ascend in the opposite lateral funiculus
They transmit impulses associated with rough touch, pain and thermal senses on the opposite side of the body.
脊神经节

22. Ascending tracts Tract Site of origin Funiculus Termination Function
Fasciculus gracilis
Spinal ganglia below segment T5
Posterior
Gracile nucleus
Convey proprioceptive and fine touch sensation of trunk and limbs
Fasciculus cuneatus
Spinal ganglia above segment T4
Cuneate nucleus
Posterior spinocerebellar
Homolateral nucleus thoracicus
Lateral
Cerebellum
Unconscious proprioception from lower limb and lower portion of trunk
Anterior spinocerebellar
Contralateral Laminae
Ⅴ~Ⅶ
Spinothalamic
Laminae Ⅰ,
Ⅳ~Ⅶ
Lateral and anterior
Dorsal thalamus
Pain, temperature and simple touch sensation of trunk and limbs

23. Descending tracts Fasciculus proprius Lateral corticospinal tract
Rubrospinal tract
Reticulospinal tract
Vestibulospinal tract
Tectospinal tract
Medial longitudinal fasciculus
Anterior corticospinal tract

24. Corticospinal tract
This tract arises from the cerebral cortex, descends through the internal capsule and brain
Stem, and is divided into:
1) Lateral corticospinal tract It decussates obliquely in the medulla oblongata and descends in lateral funiculus.
2) Anterior corticospinal tract It occupies a strip adjacent to the anterior median fissure, terminating in the bilateral anterior horns.

25. Descending tracts Tract Site of origin Funiculus Termination Function
Lateral corticospinal
Cerebral cortex
Lateral
Laminae
Ⅳ~Ⅸ
anterior horn
Voluntary movement
Anterior corticospinal
Anterior
Rubrospinal
Red nucleus
Ⅶ~Ⅶ
Excitatory of flexors
Vestibulospinal
Homolateral vestibular nuclei
Ⅶ~Ⅷ
Excitatory of extensors
Reticulospinal
Reticular formation
Anterior and lateral
Medial longitudinal fasciculus
Vestibular nuclei
Coordinate neck with eye movement
Tectospinal
Superior colliculus
Ⅵ~Ⅷ
Fasciculus proprius
Spinal cord
Anterior, lateral and posterior
Intrinsic reflex mechanism of spinal cord

27. Main functions of spinal cord
Conduction of excitations
Reflex activity

28. Reflex arc

29. Reflex arc

30. The clinical consideration
Pathologic lesion in the spinal cord can produce characteristic syndromes (abnormal masses compression, mechanical injury). Complete hemisection of spinal cord produce Brown-sequard syndrome.

31. Brown-sequard syndrome.
the signs and symptoms of patient include ipislateral motor neuron paralysis in the segments of the lesion (resulting from damage to corticospinal tract),
ipislateral loss of propriceptive, vibratory, and two point discrimination senses (resulting from damage to fasciculus gracilis and cuneatus ).
A contralateral loss of pain and temperature senses below one or two segments at the damaged level (resulting from damage to the spinothalamic tracts).

32. Thank you