Anatomy of nervous system

1. ANATOMY OF NERVOUS
SYSTEM

2. ANATOMYOF NERVOUS SYSTEM
• It is also called Neuroanatomy.
• Like other systems in the body, the nervous
system is composed of organs, principally the
brain, spinal cord, nerves, & ganglia. These, in
turn, consist of various tissues, including
nerve, blood, and connective tissue.
• It is the major controlling, regulatory, and
communicating system in the body.
• It is the center of all mental activity including
thought, learning, and memory.

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Brain
Skeletal Muscle
Spinal cord
Neurons
Neurons
Receptor
Neuron is
A Mechanism of Nervous
System Coordination &
Functions

4. ANATOMYOF NERVOUS SYSTEM
• Together with the endocrine system, the
nervous system is responsible for regulating
and maintaining homeostasis.
• Through its receptors, it keeps us in touch
with our env’t, both external and internal.
• Nervous system is organized into two major
divisions: the Central Nervous System (CNS)
and the Peripheral Nervous System (PNS).

5. • CNS: consists of the brain and spinal cord.
• PNS: consists of the 12 pairs of cranial nerves, 31
pairs of spinal nerves and associated ganglia
including the Autonomic Nervous System (ANS).
Brain
Spinal
cord
CNS
Nerves
Ganglia
PNS

6. Basic Functions of the Nervous System
Sensation: Monitors changes/events
occurring in and outside the body. Such
changes are known as stimuli and they are
monitored by receptors.
Integration: The parallel processing and
interpretation of sensory information to
determine the appropriate response.
Reaction: Motor output. The activation of
muscles or glands (via the release of
neurotransmitters).

8. CENTRAL NERVOUS SYSTEM (CNS)
• is composed of the brain and spinal cord.
• is the largest part of the nervous system.
• The brain is within cranial cavity, & spinal cord
is in spinal canal.
• The brain and spinal cord are covered by the
meninges (protective coverings).
• Brain is also protected by the skull & spinal
cord by the vertebrae.

9. THE CENTRAL NERVOUS SYSTEM
Brain
Spinal Cord

10. THE BRAIN
• is located in the cranial cavity.
• is supported & protected by the cranial bones,
meninges, & cerebrospinal fluid.
• Average adult human brain weighs in at 1.3-1.4 Kg
and is larger in male than females. In a newborn
human baby's brain weighs 350-400 g.
• Brain size represents a proportional difference in
body size; but brain size is not correlated to
intelligence but is related to the complexity of the
neural connections within the brain.
• Brain has four ventricles, cavities that are filled
with cerebrospinal fluid.

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1. Cerebrum
2. Diencephalon
3. Brain Stem
4. Cerebellum
The Brain Regions
-Brain has 4 major parts.
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12. The Brain Regions
Cerebellum
Cerebrum
Diencephalon

13. CEREBRUM

14. The Cerebrum
• makes up the largest (83%) part of the brain.
• has gyri (folds), sulci (shallow grooves), and
fissures (deep grooves) of the cerebral cortex.
• has two (right & left) cerebral hemispheres
that are separated by the longitudinal cerebral
fissure, however, deeply connected by the
corpus callosum.
• The right cerebral hemisphere controls the
left side of the body and the left one controls
the right side of the body.

15. The Cerebral Hemispheres
• Each hemisphere has an outer cortex of gray
matter surrounding an interior that is mostly
white matter, except for a few small portions.
• Deep sulci divide each hemisphere into five
lobes.
Right Cerebral
Hemisphere
Left Cerebral
Hemisphere
Longitudinal Cerebral Fissure

16. • Each cerebral hemispheres has five lobes,
namely:
1. Frontal Lobe
2. Parietal Lobe
3. Occipital Lobe
4. Temporal Lobe
5. Insular Lobe
• The main depressions that separate the lobes
are the Longitudinal cerebral fissure, Central
sulcus, Lateral cerebral fissure(sulcus),
Parieto-occipital fissure(sulcus).

17. The Lobes of Cerebral Hemispheres

18. • Central sulcus – separates the frontal and
parietal lobes.
• Parietal-occipital sulcus – separates the
parietal and occipital lobes.
• Lateral sulcus – separates the parietal and
temporal lobes.
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19. • Each cerebral hemisphere is divided into 3
regions:
Cerebral Cortex (Gray Mater)
Cerebral White Mater
Basal Ganglia (Gray Mater)
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Regions of the Cerebrum

21. Cerebral Cortex
• The cortex – superficial gray matter; accounts
for roughly 40% of the mass of the brain.
• It enables recognition of sensation,
communication, memory, understanding, and
voluntary movements.
• It has specific parts that are specialized for
specific functions, called functional areas.
• No functional area acts alone; conscious
behavior involves the entire cortex.

22. Functional Areas of the Cerebral Cortex
• Three types of functional areas are:
Motor areas – control voluntary movement
Sensory areas – conscious awareness of
sensation
Association areas – integrate diverse
information

23. Primary Motor Cortex:-located in the frontal
lobe and allows conscious control of skilled,
voluntary mov’ts.
Premotor Cortex:-located in the frontal lobe
and controls learned, repetitions, or patterned
motor skills.
Broca’s Area:-is a motor area located in the
frontal lobe and directs muscles of tongue & is
active as one prepares to speak.
Frontal eye field:-located in the frontal lobe
and controls voluntary eye movement.

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25. Somatosensory Areas:-located in the parietal
lobe. They receives information and
understand sensations such as determining
size, texture, & relationship of parts.
Visual Areas:-located in the occipital lobe.
They receives visual information from the
retinas and interpret the stimuli (e.g, color,
form, & mov’t).
Auditory Areas:-located in the temporal lobe.
They receives information related to pitch,
rhythm, & loudness and also stores memories
of sounds & permits perception of sounds.

26. Olfactory Area:-located in the frontal lobe and
consciously identifying and recalling specific
odors and telling different smells apart.
Prefrontal Area: located in the anterior portions
of the frontal lobe involved with cognition,
recall, and personality. It is necessary for
judgment, reasoning, & ethics.

27. Functional Areas

28. CEREBRAL WHITE MATTER
• Consists of deep myelinated long & short
fibers and their tracts.
• It is responsible for communication b/n the
cerebrum and the other brain regions.
• It also connects & communicates the cerebral
hemispheres, lobes, and functional areas of
the cerebrum.

29. CEREBRAL WHITE MATTER
• According to the size and functions, the
fibers can be classified as follow:
Association fibers – connect different parts
of the same hemisphere.
Commissural fibers – connect corresponding
gray areas of the two hemispheres.
Projection fibers – enter the cerebrum from
lower brain or cord centers.

30. 30
Cerebral White Matter Fibers

31. CEREBRAL WHITE MATTER
1. Association Fibers
• are the shortest fibers of the white matter
region.
• located only within each cerebral
hemisphere.
• Short association fibers: connect adjacent
gyri in the same hemisphere.
• Long association fibers: connect more
widely separated areas and lobes.
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32. Cerebral White Matter Fibers

33. Commissural Fibers
• interconnect the hemispheres.
• integrates activity of the hemispheres.
• communicate the hemispheres with each
other.
• are responsible for coordinating the activities
of the two cerebral hemispheres
• e.g, Corpus Callosum: the largest bundle of
commissural fibers.
33

34. Projection Fibers
• are the longest fibers of the white matter
region.
• connect cerebrum with the other regions of
the brain and the spinal cord.
• Afferent fibers: include the geniculocalcarine
radiation, auditory radiation and thalamic
radiations from the thalamic nuclei to specific
cerebrocortical areas.
• Efferent fibers: to the thalamus, brain stem,
or spinal cord.
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35. 35
Cerebral White Matter Fibers

36. DIENCEPHALON

37. DIENCEPHALON
• located in the central core of the forebrain.
• encloses the third ventricle.
• consists of three structures.
–Thalamus,
–Hypothalamus,&
–Epithalamus,
• These structures effectively enclose the third
ventricle.

38. Hypothalamus
Thalamus
Epithalamus
Diencephalon

39. Thalamus
-composed of bilateral masses of gray matter
held together by a mid-line commissure called
the intermediate mass.
-is egg shaped with paired, gray matter masses.
-is the largest part, makes up 80%, of the
diencephalon.
• All inputs ascending to the cerebral cortex
pass through the thalamus.
• Afferent impulses from all senses converge
and synapse in the thalamus.

40. Diencephalon

41. Thalamus

42. Thalamic Function
• It is relay station, afferent impulses from all
senses converge and synapse in the thalamus,
except those of olfactory nerves.
• Impulses of similar function are “sorted out,”
edited, and relayed as a group.
• Plays a key role in mediating sensation, motor
activities, cortical arousal, learning, and
memory.

43. Hypothalamus
• Located below the thalamus, it caps the
brainstem and forms the inferolateral walls
of the third ventricle.
• Has three regions.
Mamillary area, posteriorly
Infundibulum & Tuber cinereum, centrally
Chiasmatic region, anterioriy

44. Hypothalamic Function
Regulates blood pressure, rate and force of
heartbeat, digestive tract motility, rate and
depth of breathing.
Perception of pleasure, fear, and rage.
Regulates feelings of hunger, satiety, & body
temperature.
Regulates sleep and the sleep cycle.
Release hormones to anterior pituitary, the
ADH & oxytocin.

45. Epithalamus
• Most dorsal portion of the diencephalon;
forms roof of the third ventricle.
• Pineal gland – extends from the posterior
border and secretes melatonin.
• Melatonin – a hormone involved with sleep
regulation, sleep-wake cycles, and mood.
• Choroid plexus – a structure that secretes
cerebrospinal fluid.

46. BRAINSTEM

47. Brainstem
• constitutes 2.5% of total brain mass.
• consists of three regions as external
divisions:
1. Midbrain
2. Pons
3. Medulla oblongata
• Each region is roughly 2.5cm long.
• Its internal anatomy is similar to that of
spinal cord but contains embedded nuclei.

48. Brainstem
Brainstem
Midbrain
Pons
Medulla oblongata

49. • Internal Regions of Brainstem:
1. Tectum
2. Tegmentum
3. Basis

50. The main functions of brainstem:
It produces the rigidly programmed,
automatic behaviors necessary for our
survival.
Acts as a passageway for all the fiber tracts
running between the cerebrum and the
spinal cord.
It is heavily involved with the innervation of
the face and head b/c 10 cranial nerve are
attach to it.

51. MIDBRAIN
• Located b/n the diencephalon and the pons.
• Midbrain structures include:
Cerebral peduncles – two bulging structures
that contain descending pyramidal motor
tracts & various nuclei.
Cerebral aqueduct – hollow tube that
connects the third and fourth ventricles.
Tectum – forming the roof of the midbrain
and contains visual & auditory reflex centers.

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53. PONS
• Bulging brainstem region between the
midbrain and the medulla oblongata.
• Forms part of ant wall of the fourth ventricle.
• Forms the largest connection with
cerebellum.
• Its fibers connect higher brain centers and
the spinal cord.
• It is origin of cranial nerves V (trigeminal), VI
(abducens), VII (facial), & VIII
(vestibulocochlear).

54. MEDULLA OBLONGATA
• is the most inferior part of the brain stem.
• forms the ant wall of the fourth ventricle.
• contains the nuclei of the last 4 cranial nerves.
• has two pairs of prominent projections:
i. Olives:- are two pos longitudinal ridges of
gray matter.
ii. Pyramids:- are two ant longitudinal ridges
formed by corticospinal tracts, w/h form
the pyramidal decussation, crossover point.

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Pyramid
Olive
Cranial Nerve of Brainstem

56. CEREBELLUM

57. CEREBELLUM
• Located pos to the pons and medulla.
• Protrudes under the occipital lobes of the
cerebrum.
• Makes up 11% of the brain’s mass.
• Provides precise timing and appropriate
patterns of skeletal muscle contraction.
• Cerebellar activity occurs subconsciously.

58. CEREBELLUM

59. Cerebellum
un

60. External Anatomy of the Cerebellum
• It has two bilaterally symmetrical cerebellar
hemispheres that are connected medially by
the vermis.
• Cerebellum appears as a large sheet with
folds, called folia – transversely oriented folds.
• Externally, it has outer gray matter cortex,
surrounding the white matter.
• It has three main anatomical lobes, the Ant,
Pos, & Flocculonodular lobes.

61. Anatomical Lobes

62. Regions of the Cerebellum
• Each fold or folium contains a core of white
matter covered superficially by gray matter.
• cerebellum has 3 regions:
• Gray Matter: outer layer called the cortex.
• White Matter: inner to the gray matter.
• Intracerebellar Nuclei: are 4 masses of gray
matter embedded in the white matter.

63. Cerebellar Peduncles
• Three paired fiber tracts that connect the
cerebellum to the brain stem.
• All fibers in the cerebellum are ipsilateral.
• Superior cerebellar peduncles: connect the
cerebellum to the midbrain.
• Middle cerebellar peduncles: connect the
pons to the cerebellum.
• Inferior cerebellar peduncles: connect the
medulla to the cerebellum.

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• Cerebellum coordinates rapid
equilibrium and balance, and
it may be temporarily affected
by alcohol. These alterations
can produce ataxia – a
disturbance in balance.

65. Cerebellar Processing Function
• Cerebellum receives impulses of the
intention to initiate voluntary muscle
contraction.
• Proprioceptors and visual signals “inform”
the cerebellum of the body’s condition.
• Cerebellar cortex calculates the best way to
perform a movement.
• A “blueprint” of coordinated movement is
sent to the cerebral motor cortex.

66. SPINAL CORD

67. SPINAL CORD
• is the second division of the CNS enclosed
within the vertebral column.
• extends from the foramen magnum to L1.
• its average length is about 45 cm.
• protected mainly by the vertebral column,
meninges, and CSF.
• provides two-way communication to and
from the brain and also gives reflex
response.

68. SPINAL CORD
Brain
Spinal Cord

69. External Anatomy of Spinal Cord
• Conus medullaris – terminal portion of the
spinal cord.
• Cauda equina – collection of nerve roots at
the inferior end of the vertebral canal.
• Filum terminale – fibrous extension of the pia
mater; anchors the spinal cord to the coccyx.
• Cervical & lumbar enlargements –widens
laterally b/c of increased numbers of lower
motor neurons, where nerves serving the
upper and lower limbs emerge.

70. External Anatomy of Spinal Cord
• Posterior median sulcus – a shallow groove
that divides posterior funiculi.
• Anterior median fissure – a deep groove
that separates the anterior funiculi.
• Right & left Hemispheres – externally
indicated by the above posterior median
sulcus & anterior median fissure.
• Spinal nerves – 31 of nerves pairs attached
to the cord by paired roots.

71. Spinal Cord
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Ant Median Fissure
Pos Median Sulcus
Lumbar Enlargement
Cervical Enlargement
Conus Medullaris
Filum Terminale

72. Gray Matter in the Spinal Cord
• is surrounded by the white matter.
• consists of cell body, neural processes, and
neuroglia and has the following regions.
–Gray Commissure – connects masses of
gray matter; encloses central canal.
–Anterior Gray Horns – interneurons and
somatic motor neurons.
–Posterior Gray Horns – interneurons.
–Lateral Gray Horns – contain sympathetic
nerve fibers.

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WHITE
MATTER
Gray Matter

74. White Matter in the Spinal Cord
• surrounds the gray matter.
• consists of fibers that run in three directions
– ascending, descending, and transversely.
• divided into three funiculi (columns):
–Posterior White Columns
–Lateral White Columns
–Anterior White Columns

75. White Matter in the Spinal Cord
• Each funiculus contains several fiber tracks.
• Fiber tract names reveal their origin and
destination.
• Fiber tracts are composed of axons with
similar functions.
• Most pathways consist of two or three
neurons.
• The pathways are paired (one on each side of
the spinal cord or brain).

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WHITE
MATTER
White Matter

77. Spinal Roots & Spinal Nerves
• Each segment pertains to 4 roots.
• Ventral roots: motor outflow tracts
• Dorsal roots: largely sensory tracts
• Dorsal root (spinal) ganglia: swellings of soma
• Peripheral nerves: spinal nerves outside the
vertebral column.
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79. PERIPHERAL NERVOUS SYSTEM
(PNS)
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80. Peripheral Nervous System
• communicates b/n CNS & rest body parts.
• Formed by 31 pairs of spinal nerves & 12 pairs
of cranial nerves.
Sensory Nerve Fibers: may be somatic (from
skin, skeletal muscles or joints) or visceral
(from organs).
Motor Nerve Fibers: may be somatic nervous
system (skeletal muscles) or autonomic
nervous system (involuntary to smooth
muscle, cardiac muscle, & glands).
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81. PNC
Spinal Nerves
Cranial Nerves

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Spinal Nerves
• are 31 pairs of nerves, each connected
to spinal cord by the dorsal & ventral
roots and grouped based on the
backbone regions:
8 paired cervical nerves
12 paired thoracic nerves
5 paired lumbar nerves
5 paired sacral nerves
1 pair of coccygeal nerves

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Spinal Nerves

84. Trochlear (IV)
Trigeminal (V)
Abducens (VI)
Facial (VII)
Vestibulocochlear (VIII)
Glossopharyngeal (IX)
Vagus (X)
Hypoglossal (XII)
Accessory (XI)
CRANIAL NERVES
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CN I (Olfactory nerves)
• are pure sensory, transmit sense of smell
from nasal mucosa to brain.
• form olfactory bulb then olfactory tract.
Brain
Nasal Cavity
Olfactory
nerve

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CN II (Optic Nerves)
• are pure sensory, transmit sense of vision
from the eyes to the brain.
• Crossing over occurs at the optic chiasma.

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CN III (Oculomotor Nerves)
• are pure motor and arise from midbrain.
• innervate most of the extraocular muscles.
• Disorders of these nerves or muscles can
result in eye paralysis, such as diplopia
(double vision) or ptosis (dropping of the
eyelid).

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Oculomotor Nerve

89. CN IV (Trochlear Nerves)
• are pure motor and arise from midbrain.
• innervate one of the extraocular muscles.
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90. CN V (Trigeminal Nerves)
• arise from pons and each nerve has 3 parts:
ophthalmic, maxillary, & mandibular.
• are mixed nerve, containing both sensory part
that transmits sense of touch, T0, & pain from
the face to the brain and motor part that
innervate muscles of mastication.
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Trigeminal
Nerve
Ophthalmic
Maxillary
Mandibular

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medially deviated
eyeball
CN VI (Abducens Nerves)
• are pure motor and arise from pons.
• innervate one of the extraocular muscles,
the lateral rectus muscle.
• injury to one nerve results in medial
deviation of the eyeball.

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Facial
Nerve
CN VII (Facial Nerves)
• arise from pons and supplies facial region.
• are mixed nerve, containing both sensory part
(w/h transmits sense from the anterior 2/3 of
the tongue to the brain) and motor part (w/h
innervate facial expression muscles & salivary,
lacrimal, & nasal glands). Pons
Tongue

93. • injury to one of the two facial nerves results
in a deviation of the affected side of the face
to the normal side.
• is b/c of facial expression muscles paralysis.
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Facial Expression Muscles
Deviated
facial part

94. CN VIII (Vestibulocochlear Nerves)
• are pure sensory and extend b/n the pons and
inner ear.
• each has two parts:
i. Vestibular nerve, concerned to body
balance.
ii. Cochlear nerve, transmits sound, thus, it
is concerned to hearing.
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95. Vestibulocochlear Nerve
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96. CN IX (Glossopharyngeal Nerves)
• arise from medulla and are mixed nerves.
• Motor part supplies the swallowing muscles.
• Sensory part supplies taste, touch, heat from
pharynx & pos tongue.
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Glossopharyngeal
Nerve
Tongue
swallowing muscles

97. CN X (Vagus Nerves)
• are mixed nerves w/h arise
from medulla and descend
to thorax and abdomen.
• Sensory part supplies taste
buds in pos tongue &
pharynx.
• Motor part innervates the
thoracic & abdominal
organs.
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98. CN XI (Accessory Nerves)
• are pure motor and arise from medulla.
• innervate muscles of the larynx, pharynx, &
soft palate.
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CN XII (Hypoglossal Nerves)
• are pure motor and arise from medulla.
• innervate muscles of the tongue.
• If one nerve injured, tongue deviates to the
normal side.
Tongue deviated to left