1. Organization of the Nervous System
The Spinal Cord
Organization of the Nervous System
CNS
Brain
Spinal cord
PNS
Somatic
Autonomic
Sympathetic
Parasympathetic

2. The Spinal Cord
Position
Lies in 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

3. The Spinal Cord 1. External features: Shape:
A long cylindrical structure
Enlargements:
cervical enlargement
lumbar enlargement
Two enlargements
Cervical enlargement : corresponds to the C4 to the T1 segments
Lumbosacral enlargement : corresponds to the L2 to the S3 segments

4. 4. Conus medullaris → filum terminale → S2 → coccyx
caudal to the lumbosacral enlargement the spinal cord tapers gradully& becomes the conical termination
Filum termination:
A condensation of pia mater forms~
Cauda equina:
lumbosacral roots descend ,sourrounding the filum terminale..
4. Conus medullaris → filum terminale → S2 → coccyx

5. 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

6. It's a part of spinal cord, which is connected
Spinal segment:
It's a part of spinal cord, which is connected
with the rootlets of a pair of spinal nerve.
31 segments
8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segments

7. Corresponding relationship between spinal segments and vertebrae
spinal segments correspond to vertebrae C1-C C1-C4
C5 ~ T8, T l~ T C4 - C7, C7 ~ T3
T5 ~ T T3 ~ T6
T9-T T6-T9
L1-L T10-T12
S l~S5,Co LI 
- 0
- 1
- 2
- 3

8. 2. Internal structure The central canal Gray matter: parts:
Lateral horn
(only extends from
Tl to L3 segments.)
gray commissure
(anterior and posterior )
posterior horn
central canal
Intermediate
zone
Lateral horn
anterior horn
Gray matter
gray commissure

9. Main nuclei: anterior horn: medial group intermediate zone:
lateral group
intermediate zone:
intermediolateral nucleus
intermediomedial nucleus
posterior horn:
the nucleus
posteromarginalis
the substantial gelatinosa
the nucleus proprius:
the dorsal nucleus
(thoracic nucleus)
in segments C8~L3
the nucleus
posteromarginalis
the substantia
gelatinosa
the nucleus proprius
the dorsal nucleus
(thoracic nucleus)
Intermediomedial
nucleus:
intermediolateral
nucleus
medial group
lateral group

10. White matter
White matter contains three kinds of fibers: ascending, descending, and fasciculus proprius

11. White matter: parts: posterior funiculus lateral funiculus
posterior median sulcus
posterior lateral sulcus
lateral funiculus
anterior lateral sulcus
anterior white
commissure
anterior funiculus
anterior median
fissure

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

13. Functions:
To convey afferent impulses, which come from somatic and visceral receptors to the brain, and conduct efferent impulses from brain to effectors.
Related to reflexes

14. The brain stem

15. The brain Telencephalon Diencephalon Cerebellum Brain stem
mid-brain pons
myelencephalon

16. The brain stem Consists of midbrain pons medulla oblongata
Bulbopontine sulcus

17. 1. Three parts: midbrain, pons and medulla
Ⅰ. General features:
1. Three parts: midbrain, pons and medulla
oblongata (from superior to inferior)
2. Position: spinal cord---diencephalon--cerebellum
Ⅱ. External features:
1. Ventral surface of the brain stem
2. Dorsal surface of the brain stem

18. Located btwn the cerebrum and the spinal cord
Provides a pathway for tracts running between higher and lower neural centers.
Consists of the midbrain, pons, and medulla oblongata.
Each region is about an inch in length.
Produce automatic behaviors necessary for survival.

19. ventral surface of Medulla oblongata
Pyramid: contain pyramidal tract (corticospinal tract)
Decussation of pyramid
formed by crossing fibers of corticospinal tract
Olive : overlying inferior olivary nucleus
hypoglossal nerve
emerge from anterolateral sulcus
Glossopharyngeal n.
vagus n.
accessory n.
emerge from
retroolivary sulcus

20. dorsal surface of Medulla oblongata
Lower portion
Gracile tubercle : overlying gracile nucleus，produced by underlying gracile nucleus
Cuneate tubercle : overlying cuneate nucleus，marks the site of cuneate nucleus
Inferior cerebellar peduncle participate in the 4th ventricle

21. Medulla Oblongata
Nuclei in the medulla are associated w/ autonomic control, cranial nerves, and motor/sensory relay.
Autonomic nuclei:
Cardiovascular centers
Cardioinhibitory/cardioacceleratory centers alter the rate and force of cardiac contractions
Vasomotor center alters the tone of vascular smooth muscle
Respiratory rhythmicity centers: receive input from the pons
Additional Centers: emesis, coughing, hiccupping, and sneezing

22. Ventral surface Pons Basilar part Basilar sulcus
Bulbopontine sulcus : from medial to lateral, the abducent, facial & vestibulocochlear nerves appear
Middle cerebellar peduncle
Trigeminal nerve
Pontocerebellar trigone : the junction of medulla, pons and cerebellum

23. Pons Literally means “bridge” Wedged between the midbrain & medulla.
Contains:
Sensory and motor nuclei for 4 cranial nerves :Trigeminal (5), Abducens (6), Facial (7), &Auditory/ Vestibular (8)
Respiratory nuclei: to maintain respiratory rhythm
Nuclei & tracts that process and relay info to/from the cerebellum
Ascending, descending, and transverse tracts that interconnect other portions of the CNS

24. Dorsal surface of the brain stem
rhomboid fossa
Boundaries
Superolateral:
superior cerebellar peduncle
Inferolateral:
gracile tubercles
cuneate tubercles
inferior cerebellar peduncle
Lateral recess

25. dorsal surface of the brain stem
rhomboid fossa
Median sulcus
Sulcus limitans
Vestibular area
overlies vestibular nuclei
Acoustic tubercle
overlying dorsal cochlear nucleus
Medial eminence
Striae medullares
Facial colliculus:
overlies nucleus of abducent n. and genu of facial nerve

26. dorsal surface of the brain stem
rhomboid fossa
dorsal surface of the brain stem
Hypoglossal triangle : overlying hypoglossal nucleus
Vagal triangle : overlies dorsal nucleus of vagus nerve
Area postrema ：lies between the vagal triangle and gracile tubercles
Locus ceruleus
at the upper end of Sulcus limitans

27. Dorsal surface of Pons Superior cerebellar peduncle
Superior medullary velum
Trochlear nerve

28. Ventral surface Midbrain Crus cerebri
Interpeduncular fossa oculomotor nerves emerge from medial of crus cerebri
Posterior perforated substance

29. Midbrain Dorsal surface Corpora quadrigemina
Superior colliculus constitute centers for visual reflexes
Inferior colliculus associated with auditory pathway
Brachium of superior colliculi
Brachium of inferior colliculi

30. Dorsal surface of Midbrain
Corpora quadrigemina:
Superior colliculus
centers of visual flexes
Inferior colliculus
conduct auditory sensation
Trochlear nerve
Brachium of superior colliculus
Brachium of inferior colliculus

31. Midbrain contains a red nucleus and a substantia nigra
Red nucleus contains numerous blood vessels and receives info from the cerebrum and cerebellum and issues subconscious motor commands concerned w/ muscle tone & posture
Lateral to the red nucleus is the melanin-containing substantia nigra which secretes dopamine to inhibit the excitatory neurons of the basal nuclei.
Damage to the substantia nigra would cause what?

32. Position Fourth ventricle
Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle
Position
Situated ventral to cerebellum, and dorsal to pons and cranial half of medulla

33. Internal structures
Gray matter
Cranial nerve nuclei
Relay nuclei

34. Cranial nerve nuclei
The Cranial nerve nuclei may be divided into 7 kinds:
General Somatic motor nuclei
Special visceral motor nuclei
General visceral motor nuclei
Visceral afferent（sensory）nuclei
( general and special )
General somatic afferent （sensory） nuclei
Special somatic afferent （sensory） nuclei

35. General somatic motor nuclei
Nucleus of oculomotor n.
Nucleus of trochlear n.
Nucleus of abducent n.
Nucleus of hypoglossal n.

36. General somatic motor nuclei
Nucleus
Site
Cranial n.
Function
Nucleus of
Oculomotor n.
Midbrain Ⅲ
Supreior, inferior,and medial recti, inf. obliquus, levator palpebrae superioris
trochlear n. Ⅳ
Superior obliquus
Nucleus of abducent n.
Pons Ⅵ
Lateral rectus
Nucleus of hypoglossal n.
Medulla Ⅻ
Muscles of tongue

37. Special visceral motor nuclei
Motor nucleus of trigeminal n.
Nucleus of facial n.
Nucleus ambiguus
Accessory nucleus

38. [Special visceral] Somatic motor nuclei
Nucleus
Site
Cranial n.
Function
Motor nucleus of trigeminal n.
Pons Ⅴ
Masticatory muscles
Nucleus of facial n. Ⅶ
Facial m., platysma, posterior belly of digastric, stylohyoid, stapedius
Nucleus ambiguus
Medulla
Ⅸ,Ⅹ.Ⅺ
Skeletal m. of pharynx, larynx and upper part of esophagus
Accessory nucleus
Medulla-cervical cord Ⅺ
Sternocleidomastoid, trapezius

39. General visceral motor nuclei
Accessory oculomotor nucleus
Superior salivatory nucleus
Inferior salivertory nucleus
Dorsal nucleus of vagus n.

40. General visceral motor nuclei
Nucleus
Site
Cranial n.
Function
Accessory oculomotor nucleus
Midbrain Ⅲ
Sphincter pupillae and ciliary m.
Superior salivatory nucleus
Pons Ⅶ
Submandibular, sublingual and lacrimal glands
Inferior salivertory nucleus
Medulla Ⅸ
Parotid gland
Dorsal nucleus of vagus n.
medulla Ⅹ
Many cervical, thoracic and abdominal viscera

41. Visceral sensory nuclei
Nucleus of solitary tract

42. Visceral sensory nuclei ( general and special )
Nucleus
Site
Cranial n.
Function
Nucleus of solitary tract
Medulla
Ⅶ,Ⅸ,Ⅹ
Taste and visceral sensation

43. General somatic sensory nuclei
Mesencephalic nucleus of trigeminal n.
Pontine nucleus of trigeminal n.
Spinal nucleus of trigeminal n.

44. General somatic sensory nuclei
Nucleus
Site
Cranial n.
Function
Mesencephalic nucleus of trigeminal n.
Midbrain Ⅴ
Proprioception of head
Pontine nucleus of trigeminal n.
Pons
Tactile sensation of head
Spinal nucleus of trigeminal n.
Medulla
Pain & temperature sense of head

45. Special somatic sensory nuclei
Cochlear nuclei
Vestibular nuclei

46. Special somatic sensory nuclei
Nucleus
Site
Cranial n.
Function
Cochlear nuclei
Pons and medulla Ⅷ
Sense of hearing
Vestibular nuclei
Sense of equilibrium

47. Non- Cranial nerve nuclei
Nucleus
position
Gracile nucleus
Medulla (underneath gracile tubercle)
Cuneate nucleus
Medulla (underneath cuneate tubercle)
Pontine nucleus
Pons
Nucleus of inferior colliculus
Midbrain
Inferior colliculus superior colliculus
Red nucleus
Substantia nigra

48. White matter Ascending tracts Medial lemniscus Spinal lemniscus
Trigeminal lemniscus
Lateral lemniscus
Descending tracts
Pyramidal tract
Corticospinal tract
Corticonuclear tract

49. white matter of brain stem
The long ascending &
descending tracts
long ascending tracts:
1. Medial lemniscus
(fine touch and
proprioceptive sense)
2. Spinothalamic
Lemniscus
[superficial sensation]
3. Trigeminal lemniscus
[superficial sensation of
opposite side head and
facial ]
4.lateral lemniscus[Sense of hearing)

50. Descending tracts pyramidal system ①corticospinal tract lateral anterior ②corticonuclear tract formatio reticularis keep waking state nuclei of median raphe（5-HT）。

51. White matter — ascending tracts
Medial lemniscus -
decussation of medial lemniscus

52. White matter — ascending tracts
Spinal lemniscus

53. White matter — ascending tracts
Trigeminal lemniscus

54. White matter — ascending tracts
Lateral lemniscus

55. White matter — descending tracts
Pyramidal tract
Corticospinal tract
Corticonuclear tract

56. White matter — descending tracts
Pyramidal tract
Corticospinal tract
Corticonuclear tract

57. Reticular formation of brain stem
The reticular formation is recognized as the extensive area outside the more conspicuous fiber bundles and nuclei of the brain stem, in which the grey were intermingled with whiter matter. Its major function may sum up as follows:

58. Reticular formation of brain stem
Ascending reticular activating system (ARAS)
Motor central and vital centres
Reticulospinal tract
Cardiovascular center and respiratory center
Serotonergic rapheal nuclei