The document provides an extensive overview of the central nervous system, detailing the structure and function of the spinal cord and brainstem. It describes the anatomy, segments, and neural pathways of the spinal cord, as well as the important roles of the medulla oblongata, pons, and midbrain. Additionally, it covers the gray and white matter composition, cranial nerves, and various tracts that facilitate communication between the spinal cord and the brain.

1. Central nervous
system (BRAIN AND SPINAL
CORD)
Dr sunil pahari , 3rd year resident
Yangtze university , china

3. Spinal cord
It is elongated, slightly flattened
dorsoventrally, located in upper
2/3rd of spinal canal. It is 42-45
cm long in adults with
maximum transverse diameter
being 10-12 mm.
 Starts or continuous with
brain stem and ends at
Conus medullaris at the level
of L1.
 Conus medullaris is conical
shaped it tapers into filum
terminale consisting of pia
matter and neuroglial
elements .
 Protected by vertebras,
Meninges and a cushion of
CSF

6. Enlargement of spinal cord
 In thoracic region it is almost
circular.
 In cervical and lumbosacral area it is
enlarged due to greatly increased
nervous neurons in number.
 The cervical enlargement includes
segments C4-T1 with most of the
spinal nerves forming brachial
plexus
 Segments L2-S3 are included in
lumbosacral enlargement and the
corresponding nerves constitute
most of lumbosacral plexuses.

7. External Longitudinal fissures and sulci
1. Anterior median (ventral)
fissure
2. Posterior median (dorsal)
sulcus
3. Dorsal and ventral nerve root
4. Lateral sulcus

8. Segments of spinal cords
 The part of spinal cord
associated with emergence of a
pair of spinal nerves is called a
segment of spinal cord.
 Spinal cord is divided into 31
segments
 8 cervical
 12 thoracic
 5 lumbar
 5 sacral
 1 coccygeal
 They vary in length and are
about twice as long in the mid
thoracic region as in cervical or
upper lumbar area.
 There are no sharp boundaries
within them

9. Vertebral Level of spinal cord segments
 In the third month of fetal life the spinal
cord fills the length of vertebral canal but
from then on vertebral column grows more
rapidly than the spinal cord.
 At birth spinal cord extends to L3 while in
adults it ends at the lower border level of
body of L1. It is important in surgery.
 A dorsal and ventral root unite to form a
spinal nerve which emerge from vertebral
canal via corresponding Intervertebral
foramina.
 Lumbar and sacral roots descend for a
considerable distance in subarachnoid space
before reaching their respective
Intervertebral foramina.
 The large number of lumbosacral roots
surrounding the filum terminale is known as
cauda equina.

11. Lumbar puncture

12. Internal Structure of Spinal Cord Grey matter
 The Grey matter is
rich in nerve cell
bodies, which form
longitudinal column
along the cord
 Its form and quantity
varies as its proportion
to white matter is
greatest in
lumbosacral and
cervical region.
 In transverse section,
the column form a “H”
–shaped appearance in
the central regions of
the cord.

13. Columns Of Gray Matter and Central Canal
 It consists of the cell columns or horns
 Around the central canal is the grey commissure, connecting the grey matter of two sides. It
encompasses the central canal, which is lined with ependymal cells and filled with CSF. It opens
into inferior portion of 4th ventricle.
 Canal usually disappears in adults except at cervical level.
The Horns:
 The posterior horn extends posterolaterally, Somatic sensory nucleus .
 The anterior horn extends anterolaterally, Somatic motor nucleus .
 Lateral horn b/w the anterior and posterior from T1 to L3 (anterior portion is General visceral
motor; posterior portion is General visceral sensory)

14. Laminae in Gray Matter
 Based upon the cytoarchitecture of
neuronal cell bodies, a cross section of gray
matter is classified into ten Rexed’s
Laminae
They are:
 Lamina I Posteromarginal Nucleus
 Lamina II Substantia Gelatinosa of Rolando
 Lamina III
 Lamina IV, V, VI ----- Nucleus Proprius
 Lamina VII
 - Intermediate Gray
 - Intermediolateral cell column (ILM)
 - Clarke’s column (Nucleus dorsalis)
 - Intermediomedial cell column (IMM)
 Lamina VIII
 Lamina IX ---------- Anterior Horn (Motor)
Cell
 Lamina X ----------- Gray Commissure

15. White matter
 Surrounds the gray matter and is rich in
nerve cell processes, which form large
bundles or tracts that ascend and descend
in the cord to other spinal cord levels or
carry information to and from the brain.
 It consists of ascending ,descending fibers
(tracts), and fasciculus proprius
 It is customary to divide spinal cord into
three pairs of funiculi.
1. The posterior funiculus lies between the
posterior horn and posterior median
septum.
2. The lateral funiculus lies between the
dorsal and ventral horns.
3. The anterior funiculus lies between the
anterior median fissure and the
emerging ventral rootlets.
 Anterior to the grey commissure is the
ventral white commissure . It connects
the white matter on both sides.

16. Neural pathways
 In general, neural pathway (neural tractor
fasiculi) indicates the functional fiber
bundles having the same origin, course
and termination.
 Serve as to join the spinal cord with the
brain. Long tracts connect the spinal cord
with the brain
1. Ascending tracts carry sensory impulses
from spinal cord to the brain.
2. Descending tracts carry the motor
impulses from the brain to spinal cord.
 Long tracts tend to be located
peripherally, while shorter propriospinal
tracts tend to be situated adjacent to
gray matter.

17. Fasciculus propius
• Ascending and descending
association fiber systems of the
spinal cord which lie deep in the
anterior, lateral & posterior
funiculi adjacent to the gray
matter.
• These neurons are confined to
spinal cord and constitute the
propriospinal or intersegmental
tracts. Mostly they are located in
laminae V-VIII.
• Fasciculi proprii aka Flechsig's
fasciculi or Ground bundles
consist of anterior, lateral &
intersegmental fasciculi

18. Tracts of the Spinal Cord
1. Fasciculus Gracilis
2. Fasciculus Cuneatus
3. Tractus spinocerebellaris dorsalis
4. Tractus corticospinalis lateralis
5. Tractus spinothalamicus lateralis
6. Tractus spinocerebellaris ventralis
7. Tractus rubrospinalis
8. Tractus spinotectalis
9. Tractus corticospinalis anterior
10. Tractus olivospinalis
11. Tractus spinoolivaris
12. Tractus tectospinalis
13. Tractus reticulospinalis
14. Tractus vestibulospinalis
15. Tractus spinothalamicus anterior
16. Raphe-spinal & Hypothalamospinal fibers

19. Ascending tracts
• A . Spinothalamic tract
• B. Dorsal / Posterior column
• C. Spinocerebellar tract

20. Ascending Tract
Dorsal column (Fasciculus gracilis and cuneatus)
 Modality: position and vibration
sens.
 They ascend without crossing in
posterior funiculus of spinal cord
to lower brain stem.
Fasciculus gracilis: , conducts lower
half of body. I
Fasciculus cuneatus: lies between
fasciculus gracilis and dorsal
gray column, transmits input
from upper half of body .
 The posterior column contains
fibers from all segments of
ipsilateral half of the body
arranged in an orderly fashion
from medial to lateral, called as
somatotopic organization

21. Spinothalamic tract
 Modality: Pain & Temperature
Sensation, Touch.
Anterior spinothalamic tract: located
in anterior funiculus.
Lateral spinothalamic tract: located in
lateral funiculus .

22. Spinocerebellar tract
The spinocerebellar tract is a set
of axonal fibers originating in the spinal
cord and terminating in the ipsilateral
cerebellum .
function- co ordination of movement.
Posterior spinocerebellar tract:
Anterior spinocerebellar tract:

23. Descending Tracts
corticospinal tract
Important for controlling of voluntery
movement.
 This system arises from cells in
precentral, motor cortex, the
postcentral gyrus and adjacent parietal
cortex descends throughout the
internal capsule and brain stem .
 It divides into three tracts:
1. Lateral corticospinal tracts: 75- 90%
of fibers.
2. Anterior corticospinal tracts
3. Anterolateral corticospinal tracts of
Barnes: uncrossed corticospinal
fibers of lateral tract

24. Function of Corticospinal Tract
 Lateral tract control distal limb
muscles of hand and foot
 Anterior tract . It also projects to
cervical and upper thoracic spinal
cord and thus may be preferentially
involved in control of neck, shoulder
and upper trunk muscles.
 Anterolateral tract provide synaptic
input to lower motor neurons
controlling axial muscles involved in
maintaining body posture.

25. • Reticulospinal tract- The reticulospinal tract that descends from the
reticular formation(a diffuse network of nerve pathways in the
brainstem connecting the spinal cord, cerebrum, and cerebellum,
and mediating the overall level of consciousness.) in two tracts to
act on the motor neurons supplying the trunk and proximal limb
muscles.
• Rubrospinal tract- controlling limb muscle and regulating voluntary
movement.
• Vestibulospinal tract- maintaining balance
• tectospnal tract- visual and auditory stimulation .

26. brain

27. Brain stem
 The major divisions of the brainstem:
medulla oblongata, the pons and midbrain
 It is stalk like in shape and connects the
narrow spinal cord with expanded forebrain
 The superior boundary is optic tract while its
inferior boundary is upper border of first
cervical nerve roots.
Three important functions
1. Serve as conduct for tracts, connecting
brain and spinal cord.
2. Contains important reflex centers
associated with CVS and control of
respiration, also associated with control of
consciousness.
3. Contains important nuclei of cranial nerve
III through XII

28. Medulla oblongata
• The medulla oblongata (or medulla) is located in the hindbrain, anterior to
the cerebellum. The medulla oblongata is a cone-shaped neuronal mass
responsible for multiple autonomic (involuntary) functions ranging from
vomiting to sneezing. The medulla contains the cardiac, respiratory,
vomiting and vasomotor centers and therefore deals with the autonomic
functions of breathing, heart rate and blood pressure.

30.  It connects pons with spinal cord. The junction b/w medulla and
spinal cord is at the level of foramen magnum .It is conical in
shape, broad extremity being directed superiorly. The central
canal of spinal cord continues upward into lower half of medulla,
in the upper half it expands as the cavity of 4th ventricle.
 Anterior median fissure divides medulla into Right and Left half
symmetrically .
 Pyramid is located beside the Anterior median fissure,
 Olive is located lateral to the Pyramid which are oval elevations
produced by the underlying inferior olivary nuclei. Posterior to
olives are inferior cerebellar peduncles which connect medulla to
cerebellum.
 Rootlets of Hypoglossal nerve emerge from between the Pyramid
and Olive
 In the groove b/w the olive and inferior cerebellar peduncle
emerge the roots of Glossopharyngeal ,Vagus and Accessory
emerge from superior to inferior.
 The posterior surface of superior half of medulla forms the lower
part of floor of 4th ventricle(rhomboid fossa) while posterior
surface of inferior half is continuous with posterior half of spinal
cord. On each side of midline there is gracile tubercle and lateral
to it is cuneate tubercle. Superior to gracile tubercle is inferior
cerebellar peduncle.

31. pons
 Pons is convex and is continuous
laterally with the cerebellum . It connects
medulla oblongata to midbrain. It is
about 2.5 mm long
 It is superior to medulla and is separated
by Pontomedullary sulcus.
 Ventral surface of pons is closely
associated with four pairs of cranial
nerves Ⅴ, Ⅵ, Ⅶ, Ⅷ
 Three pairs of cranial nerves Ⅵ,Ⅶ,Ⅷ
emerge from the Pontomedullary sulcus .
 The posterior surface of pons is hidden
from view by cerebellum. It forms upper
half of floor of 4th ventricle and is
triangular.

32. midbrain
 The midbrain is smallest and least differentiated brain stem
segments. It connects pons and cerebellum with forebrain. It is
traversed by a narrow channel, the cerebral aqueduct which is
filled with CSF.
 On posterior surface Four rounded eminences are arranged in
pairs, are called superior and inferior colliculi. (Quadrigemina
corpora).
 The superior colliculi are associated with the optic system,
 The inferior colliculi are associated with the auditory pathway .
Cranial nerve Ⅳ ( trochlear nerve ) emerges from the midbrain.
 On the dorsal surface of brain stem, there are pairs of superior,
middle and inferior peduncles which connect brainstem with
cerebellum. Oculomotor nerve emerging from the medial to the
cerebellar peduncle.

33. Rhomboid fossa
• The anterior part of the fourth
ventricle is named, from its
shape, the rhomboid fossa,
and its anterior wall, formed
by the back of
the pons and medulla
oblongata, constitutes the
floor of the fourth ventricle.

34. Internal structure
Compared with spinal cord, the internal structure of brain stem appears the
following characters：
1. The structure of medulla oblongata’s inferior part is similar to spinal cord. The
central canal still remains.
2. The gray matter of brain stem don’t continue and form gray column which run
lengthwise through the total length of brain stem like that in spinal cord, but get
together forming all kinds of nucleus separated with each other.
3. The nucleus groups of gray substance of brain stem all link with cranial nerve
basically.
4. it contains many important nuclear groups of vital center, such as center of
heartbeat, blood pressure and respiratory.

35. Grey matter of brain stem
1.Nuclei of cranial nerves
2.non-cranial nerves
nuclei
3. relay nucleus
4.reticular nucleu
somatic motor fiber
visceral motor fiber
visceral sensory fiber
somatic sensory fiber
1. nuclei of cranial nerves
（1）general somatic motor
nuclei (4 pairs)
* dominate skeletal muscle
（lingual muscle，
extraocular muscles）
nucleus of oculomotor nerve
nucleus of trochlear nerve
nucleus of abducent nerve
nucleus of hypoglossal nerve

36. （2）special visceral motor nuclei (4 pairs)
-Motor nucleus of trigeminal nerve
-Nucleus of facial nerve
-Nucleus ambiguus ( send fiber to
glossopharyngeal, vagus and
accessory)
-Accessory nucleus ( supply SCM
muscle and trapezius)
（3）general visceral motor
nuclei (4 pairs)
Dominate smooth muscle、cardiac
muscle and glands
-accessory nucleus of oculomotor nerve
-superior salivatory nucleus
-inferior salivatory nucleus
-dorsal nucleus of vagus nerve

37. （4）general and special visceral sensory nucleus (1 pair)
Receives visceral afferent fibers from
the facial, glossopharyngeal and
vagus nerves, which enter the brain
stem by passing through the
posterolateral sulcus.
Nucleus of solitary tract

38. Non cranial nerve nuclei
1) Gracile and cuneate nuclei- touch and vibration
2) Inferior olivery nuclei - give olive cerebellar fiber
which take part in controlling and regulating
movement .
3) Pontine nuclei- relay station for cerebral cortex to
cerebellum.
4) Nucleus of inferior colliculus- relay station for auditory
pathway.
5) Nucleus of superior colliculus- receive fiber from optic
tract and visual cortex .
6) pretectal nucleus – receive fiber fron retina through
optic tract . Related to the pupillary light reflex.
7) Red nucleus- take part in somatic movement.
8) Substantia niagra – release of dopamine , tremor,
parkinsons dideases .

39. 1. long ascending tracts
(1) medial lemniscus-gracile and cuneate nuclei → ventral
posterolateral nuleus of thalamus
Conducting proprioceptive impulses.
(2) spinothalamic lemniscus-Conducting the impulses of pain,
thermal and tactile sensations from opposite side of body.
(3) lateral lemniscus- Cochlear nuclei → trapezoid body →
inferior colliculus → nucleus of medial geniculate body
Conducting the auditory senses on both sides.
(4) trigeminal lemniscus-Conducting the tactile, pressure, pain
and thermal impulses of head and face of the opposite side.
(5) medial longitudinal fasciculus – extraocular
muscle , coordinate eye movement
2. long descending tracts
(1) pyramidal tract 1. corticospinal tract
2. corticobulbar tract
(1) tectospinal tract- the tectospinal tract (also known as
colliculospinal tract) is a nerve pathway that coordinates head and eye
movements.
Voluntary movement of skeletal
muscle

40. Reticular formation
• The reticular formation is a set of interconnected nuclei that are
located throughout the brainstem. The reticular formation is not
anatomically well defined because it includes neurons located in
diverse parts of the brain.
Traditionally the nuclei are divided into three columns
• In the median column – the raphe nuclei
• In the medial column – gigantocellular nuclei (because of larger size
of the cells)
. In the lateral column – parvocellular nuclei
function
1. Somatic motor control –
2. Cardiovascular control –
3. Pain modulation
4. Sleep and consciousness – .
5. Habituation

41. cerebellum
• The cerebellum ( little brain)
though small in size , serve
important functions for
maintaining tone ,posture and
equilibrium of the body .
• it is situated in posterior cranial
foss behind the pons and
medulla.
EXTERNAL FEATURES:
• Two cerebellar hemisphere
united by median vermis
• each hemisphere is divided into
three lobes: anterior , middle/
posterior, flocculonodular lobe.
PARTS OF CEREBELLUM
• Horizontal fissure , primary
fissure. Uvulonodular fissure.

43. Morphological and functional division of cerebellum
• 1. Archiocerebellum- it is made up
of flocculonodular lobe and
lingula.it controll the bilateral
movement used for locomotion
and maintanance of equilibrium.
• 2. paleocerebellum- it is made up
of anterior lobe ,pyramid and
uvula. Its connection are chiefly
spinocerebellar. It controls tone,
posture, and crud movement of
limb.
• 3. neocerebellum- made up of
posterior middle lobe. It is
concerned with regulation of fine
movement.

46. Ventricular system

47. DIENCEPHALON
Between the brain stem and the
hemispheres of the cerebrum
-dorsal thalamus
-hypothalamus
-Metathalamus ( MGB & LGB)
-Epithalamus (pineal BODY)
-subthalamus (ventral thalamus)

48. THALAMUS
• Large mass of grey matter situated
in the lateral wall of third venticle.
• The grey matter is divided to form
several nuclei.
anterior nuclei , medial nuclei ,
ventral nuclei, intralaminar nuclei .
- proprio ceptive impulses ascend
throught it .
METATHALAMUS
- Medial geniculate body - auditory
impulse to cerebral cortex
- lateral geniculate body - visual
pathway to occipital cortex

49. thalamus

50. hypothalamus
• It lies below the dorsal thalamus
and forms the floor and inferior part
of lateral wall of third ventricle.
• When observeed from below
,hypothalamus is seen to be related
to the following structure from
anterior to posterior –
• optic chiasma
• tuber cinerium
• infundibulum
• mamillary body
• Function- endocrine fxn ,
neurosecretion ,tempreature
regulation, regulation of food and
water intake, emotion fear ,
pleasure reward.
Paraventricular nucleus
supraoptic nucleus

51. Telencephalon ( cerebrum)
• Largest part of brain .
• Cerebrum is made up of two
hemispheres which are incompletely
seperated from each other by
median longitudinal fissure .
• the hemisphere connected together
by corpous callosum
EXTERNAL FEATURE
1) Three surface- superiolateral ,
medial ,inferior
2) four border- superomedial,
inferiolateral,medialorbital, medial
occipital
3) Three poles – frontal, occipital ,
temporal
4) four lobes – frontal ,parietal,
temporal, occipital

52. Sulcus and gyrus of cerebrum

54. Limbic system

55. Cerebral cortex
• The cerebral cortex is the cerebrum's
(brain) outer layer of neural
tissue in humans and other mammals. It
is divided into two cortices, along
the sagittal plane: the left and
right cerebral hemispheres divided by
the medial longitudinal fissure. The
cerebral cortex plays a key role
in memory, attention, perception, aware
ness, thought,language,
and consciousness.
• Divided into 6 layers
. molecular
• external granular
• external pyramidal
• Internal granular
• Internal pyramidal
• polymorphic

56. Functional localization of cerebral cortex

57. • A) primary somato sensory
area- it occupies the
postcentral gyrus and
posterior part of para
centra gyrus.
• B) primary motor area – it
is located into pre central
gyrus .

58. Medullary area
• A..Corpus callosum - is the
largest commisure of the
brain which connect two
cerebral hemisphere.
• 4 parts - rostrum ,genu ,
trunk and splenium .
• Function- help in
coordinating activity in two
hemisphere.
• B.. Anterior commisure
• C.. fornix

59. Basal ganglia
• A region of the base of the brain
that consists of three clusters of
neurons (caudate nucleus,
putamen, and globus pallidus) that
are responsible for involuntary
movements such as tremor,
athetosis, and chorea. The basal
ganglia are abnormal in a number
of important neurologic conditions,
including Parkinsons
disease and Huntington's disease.
• Corpus striatum= putamen +
caudate
• Corpous lentiform= putamen + gp