1. NERVOUS SYSTEM
Chona Araga, M.D.

2. - Nervous System is a group of tissues
composed of highly specialized cells
possessing the characteristics of
excitability and conductivity

3. MORPHOLOGICAL DIVISIONS:
A. CENTRAL NERVOUS SYSTEM
1. Brain
2. Spinal cord
B. PERIPHERAL NERVOUS SYSTEM
1. Cranial Nerves (12 pairs)
2. Spinal Nerves ( 31 pairs)
3. Autonomic Nervous System

5. FUNCTIONAL DIVISIONS:
A. SOMATIC EFFERENT
- innervating somatic structures like
skeletal muscles and skin.
B. VISCERAL EFFERENT
- innervating visceral or involuntary
structures like smooth muscles, cardiac
muscles and glands. This is the autonomic
nervous system

6. TYPES OF CELLS IN THE
NERVOUS SYSTEM
- The nervous system is composed of a
special tissue containing two major
types of cells:
1. Neurons
- the active conducting elements
2. Neuroglia
- the supporting elements

7. NEURON
- basic unit of the nervous system which
conducts electrical impulses from one part
of the body to another
-consists of a cell body (perikaryon),
containing a single nucleus, and processes
transmitting impulses to and from the body

8. TWO TYPES OF
PROCESSES
 A. DENDRITES – group of short, unsheathed
processes arranged like branches of a tree that
transmit impulses toward the cell body
 B. AXONS – a single, elongated sheathed
process conducting impulses away from the
cell body.
 ACCESSORY CELLS – the non nervous
elements consist of blood vessels, connective
tissue, and supporting cells known collectively
as neuroglia

10. SYNAPSE
- point of connection between neurons.The axon of one
neuron makes functional contact with dendrites of another
neuron.
Main neurotransmitters :
1. epinephrine (adrenalin)
2. norepinephrine (nor adrenaline)
3. acetylcholine
NERVE IMPULSE
A. MYELIN SHEATH – insulating material covering axons in central and
peripheral nervous system
- the thicher the myelin sheath is, the faster the passage of nerve
impulse will be.
- the electril impulse jumps from node to node in myelin sheath instead
of traveling continuously along the nerve fiber. (SALTATORY
CONDUCTION OF IMPULSES)

14. CENTRAL NERVOUS SYSTEM
- Central nervous system includes the brain and spinal cord.
- It is divided grossly into gray and white matter:
A. Gray matter
- so called because of its appearance and preponderance
of nerve cell bodies and true dendrites.
B. White matter
- composed chiefly of myelinated nerve fibers
- white in gross appearance - and few, if any, nerve cell
bodies.
- In the spinal cord an H-shaped central region of gray
matter is surrounded by white matter

16. BRAIN
- part of the central nervous system
contained within the skull.
- most complex and largest mass of nervous
tissue in the body and contains literally
billions of nerve cells.
- The average weight of the human brain in
the adult is approximately 1380gms in the
male and 1250 grams in the females.

17. EMBRYOLOGICAL DIVISIONS
OF THE BRAIN
1. Forebrain (Prosencephalon)
a. Telencephalon (cerebrum)
b. Diencephalon ( thalamus, hypothalamus, epithalamus,
subthalamus)
2. Midbrain (Mesencephalon)
a. Corpora quadrigemina (tectum) - 2 superior colliculi
2 inferior colliculi
b. Cerebral peduncles
c. Cerebral Aqueduct of Sylvius (iter)
3. Hindbrain (Rhombencephalon)
a. metencephalon (cerebellum, pons)
b. myelencephalon (medulla oblongata)

18. 1. PROSENCEPHALON
A. TELENCEPHALON (CEREBRUM)
- represents seven-eights of weight of
brain
- responsible for discriminatory
identification of and integration of
sensory information, memory
reasoning,
- for use of language
- for emotional behavior
- for initiation of movement

19. FISSURES OF CEREBRUM
1. Longitudinal Fissure
- runs from the posterior to the anterior
aspects almost completely dividing it
into 2 hemispheres.
- each hemisphere has a full set of
centers for sensory and motor
activities of the body, and each
associated with one side of the body.
- the hemispheres are connected in the
midline by the corpus callosum

21. 2. Lateral Sylvian fissure
- between the frontal
and parietal lobes
above and temporal
lobe below.
- associated with
centers for speech
and hearing.

22. 3. Central Sulcus (Rolandic
Fissure)
- between frontal and
parietal lobes-
associated with
centers for both
motor and sensory
functions.

23. 4. Transverse fissure
- between the cerebellum
and the cerebrum
5. Parieto - occipital
fissure
- between the occipital
and parietal lobes.
6. Calcarine fissure
- found in the occipital
lobe perpendicular to
parieto occipital fissure
around which is the
visual center.

24. LOBES OF THE CEREBRAL
CORTEX
1. Frontal Lobe
- includes all the
cortex lying anterior
to the central sulcus
of Rolando and above
the lateral sulcus
Sylvius
- center for motor
functions and
personality

25. 2. Parietal Lobe
- lies posterior to
central sulcus of
Rolando and above
lateral Sylvian
fissure.
- center for sensory
functions

26. 3. Temporal Lobe
- lies beneath the
lateral sulcus of
Sylvian
- center for hearing
and olfaction

27. 4. Occipital Lobe
- occupies the
posterior extremity
of the cerebral
hemisphere behind
parieto-occipital
fissure
- visual center

28. 5. Insula ( Island of Reil)
- exposed when the
lips of lateral
Sylvian fissure are
separated

29. FUNCTIONS OF THE CEREBRUM
1. seat of advanced intellectual functions
like memory storage, recall, learning
and reasoning for comprehension and
execution of language.
2. perception of all sensations and
sites where one modality of sensation
can be integrated with others.
3. initiation of movements

30. FUNCTIONAL AREAS OF THE
CEREBRUM
2. Primary Motor Area or
Pre-central gyrus
- lies in the frontal lobe
immediately anterior to the
central sulcus
- controls voluntary
movements in the opposite
side of body.
- the body is represented
with head down and lower
extremities up and medially
in the cerebrum.
- Brodmann's area 4

31. 2. Pre-motor Area
- in front of the
motor area
- exerts a
controlling influence
over the motor
area, ensuring an
orderly series of
movements
necessary for
speech.

32. 3. Pre-frontal Area
- concerned with
behavior, character
and emotional state
of the individual.
- concerned with
foresight, good
judgment, abstract
thinking.

33. 4. Primary sensory/Somesthetic Area
or Post-central gyrus
- lies behind the central
sulcus of Rolando in
parietal lobe
- sensations of pain,
temperature, pressure
and touch, position and
movement sensation
from opposite side of
body are received and
interpreted here.
- Brodmann's area 3,1,2

34. 5. Motor speech area
- lies in inferior
frontal gyrus of
dominant
hemisphere
- Broca's area
(Brodmann's area
45, 44)

35. 6. Sensory speech area:
- lies in temporal lobes
posterior to auditory
area of dominant
hemisphere
- Wernicke's area
(Brodmann's area
22)

36. 7. Auditory or Hearing Area
(transverse gyri of Heschl)
- lies below lateral
sulcus within the
temporal lobe
- center for hearing
- Brodmann's area 41
& 42

37. 8. Visual area:
- around the calcarine
fissure, including
greater part of the
occipital lobe
- Brodmann's area 17

38. 9. Olfactory or smell area
- within the temporal
lobe

39. 10. Taste Area
- above lateral sulcus
into the deep layers
of the sensory area

40. BASAL GANGLIA
masses of gray matter
embedded in the white matter
of the cerebral hemispheres
- include the caudate nucleus
(medial portion) and the
putamen and globus
pallidus called lentiform
nucleus.
- constitute the corpus striatum
- Basal ganglia play a role in the
control of motor function, and
injury produces unilateral or
bilateral tremor, rigidity and
uncontrolled aimless
movements.

41. B. DIENCEPHALON
1. Thalamus
- paired mass of gray matter situated
below corpus callosum.
- subcortical sensory integrating
cortex
- relay center for sensory impulses
(except olfactory) from peripheral
receptors to cerebral cortex;
responsible for crude awareness of
sensation
- processes and relays coordinating
motor impulses from the basal
ganglia and cerebellum to the
cerebral motor cortex.
- relay and integration center for
emotional behavior

42. 2. Hypothalamus
- involved in the
regulation of body
temperature, feeding
activities,concentration
and volume of
extracellular fluid,
autonomic nervous
system responses,
endocrine functions.

43. 2. MESENCEPHALON
- connects the
forebrain and
hindbrain
- concerned with motor
coordination
- connects the pons
and the cerebellum
with the cerebrum
consists of:

44. a. Cerebral Peduncles (found anteriorly)
- pair of cylindrical bodies made up of nerve
fiber tracts which connect the forebrain
with the hindbrain.
b. Corpora Quadrigemina ( found posteriorly)
- 4 rounded nuclear masses
1. superior colliculi
- upper 2; for visual reflexes
2. inferior colliculi
- lower 2; for auditory reflexes

47. 3. RHOMBENCEPHALON
CEREBELLUM ( Part of
metencephalon )
- oval in shape with a
central constriction and
lateral expanded
portions.
- the constricted central
portion is called the
vermis (Latin of worm)
and the lateral
expanded portions the
hemispheres

48. - divided into lobes by deep
and distinct fissures,
these lobes include the:
a. anterior concerned
with the function
of
b. posterior / movements
c. flocculonocular lobes
- concerned with the
function of equilibrium

50. PONS ( Part of metencephalon )
- lies anterior to the
cerebellum and between
the midbrain and
medulla.
- bridge-like structure,
consisting almost
entirely of white matter
linking the various parts
of the brain

51. MEDULLA OBLONGATA
( myelencephalon )
- continuous with the spinal cord
inferiorly and with the pons
superiorly
- lies ventral to the cerebellum
- has a number of vital regulatory
and reflex centers, including
those controlling the circulatory
system, breathing, swallowing,
vomiting, coughing, sneezing.

52. VENTRICLES OF THE BRAIN
- spaces inside brain filled with cerebrospinal fluid.
- the Ventricular System includes:
1. lateral ventricle
- found inside the cerebral hemispheres
- each lateral ventricle communicates with the third ventricle
by way of an interventricular foramen (foramen of
Monroe)
2. third ventricle
- small, slitlike cavity in the center of the diencephalon in
between the 2 thalamic continuous with the cerebral
aqueduct of Sylvius, a canal which passes through the
midbrain.
3. fourth ventricle
- lies between the cerebellum on the posteriorly side and the
pons and medulla on the anteriorly side.
- communicates with subarachnoid space through Foramen
of Luschka and Magendie

54. MENINGES
-Three membranes collectively known as
the meninges provide protection to the
brain and spinal cord
- from outside in, these are the:
A. Dura mater
B. Arachnoid mater
C. Pia mater

56. A. DURA MATER
- the dura mater (latin for
hard mother), the outer
meninx, is made of
dense, fibrous tissue.
- There are 2 portions of
the dura mater
1. cranial
2. spinal

57. B. ARACHNOID MATER
- delicate serous membrane located
between the dura and pia.
- As the name implies, it has the microscopic
appearance of a spider web
- the cranial portion invests the brain loosely
and, with the exception of the longitudinal
fissure, it passes over the various
convolutions and sulci and does not dip
down into them

59. C. PIA MATER
- The pia mater (gentle mother) is a vascular
membrane consisting a plexus of fine blood
vessels held together by areolar connective
tissue.
- The cranial portion invests the surface of the
brain and dips down into the sulci.

61. CEREBROSPINAL FLUID
- the cerebrospinal fluid circulating within
the ventricles, the central canal of the
spinal cord and also within the
subarachnoid space.
- colorless, with a composition similar to
that of lymph

62. SPINAL CORD
- the elongated and almost
cylindrical part of the CNS,
which lies within the vertebral
canal.
- is continuous with the medulla
oblongata above and extends
from the level of foramen
magnum to the lower border
of 1st lumbar vertebra in
adult and level of L3 vertebra
in children.
- average length: 45 cm

63. - 2 enlargements:
1. cervical enlargement (where nerve supply of arms
arises from)
- level of 4th cervical to 2nd thoracic vertebrae
2. lumbar enlargement (where nerve supply of legs arises
from)
- level of 10th thoracic vertebra; widest at the
12th thoracic vertebra
- it narrows down as a conus medullaris, where it
gives rise to the thread-like filum terminale that
terminates in the first coccygeal vertebra.
- the lumbar and sacral spinal nerves descend along
the filum terminale in a bundle known as the cauda
equina

65. PERIPHERAL NERVOUS
SYSTEM:
SPINAL AND CRANIAL NERVES
I . SPINAL NERVES
- a bundle of nerve fibers
attached to spinal cord
- 31 pairs of nerves called spinal
nerves arise from the spinal cord
along almost its entire length and
emerge from the vertebral canal
through the intervertebral foramina

66. 1. dorsal root
- containing fibers of sensory neurons
2. ventral root
- containing fibers of motor neurons
- these 2 roots join together to form
spinal nerve

67. - There are eight pairs
of cervical spinal
nerves, 12 thoracic,
5 lumbar, 5 sacral,
1 coccygeal

69. PLEXUSES
- group of nerve fibers from ventral rami of cervical , lumbar and
sacral spinal
nerves. Posterior rami never form plexuses.
1. Cervical Plexus
- formed by the first 4 cervical nerves (C1C2C3C4)
- this supplies the back and sides of the head and the front of the
neck
- gives off the phrenic nerve to the diaphragm
2. Brachial Plexus
- lower 4 cervical (C5C6C7C8) nerves and 1st thoracic (T1)
supplies the skin and muscles of the upper limb
- gives off large nerves: circumflex, radial. median ulnar and
musculocutaneous nerves.

70. 3. Lumbar Plexus
- from L1 -L4 spinal nerves
a. Obturator Nerve
- arising from anterior division of L2L3L4 spinal nerves
- supplies the muscles and skin on medial aspect of thigh
b. Femoral nerve
- arising from the posterior divisions of L2L3L4 spinal nerves
- supplies muscles and skin on anterior aspect of the thigh

71. 4. Sacral Plexus
- from L4L5S1S2S3
spinal nerves
- the largest branch of
which is the sciatic
nerve (the largest
nerve in the body)

72. The thoracic spinal nerves do not form plexuses.
T1 - T11 spinal nerves - INTERCOSTAL NERVES
T 12 spinal nerves - SUBCOSTAL NERVE
Sciatic Nerve divides into:
a. tibial nerve
- supplies most of the posterior thigh
muscles, posterior leg and sole by dividing
into medial and lateral plantar nerves
b. common peroneal nerve
- supplies short head of biceps femoris and
anterolateral leg and dorsum of the foot.

73. II. CRANIAL NERVES
- The cranial nerves are 12 pairs of symmetrically arranged
nerves attached to the
brain.
- The cranial nerve includes the following:
1. Olfactory (I)
2. Optic (II)
3. Oculomotor (III)
4. Trochlear (IV)
5. Trigeminal ( V)
6. Abducens (VI)
7. Facial ( VII)
8. Vestibulocochlear (acoustic) (VIII)
9. Glossopharyngeal (IX)
10. Vagus (X)
11. Accessory (XI)
12. Hypoglossal (XII)

76. CLASSIFICATION OF CRANIAL
NERVES
SENSORY NERVES
- carry impulses towards brain. Also
called afferent fibers
- cranial nerves I (olfactory), II (optic)
and VIII (vestibulocochlear)
however carry only sensory fibers ( from
the nose, eye, and ear, respectively)

78. MOTOR NERVES
- carry impulses away from the brain.
Also called efferent fibers
- cranial nerves III (oculomotor), IV
(trochlear) and VI (abducens), which
supply the eye muscles, XI
(accessory) and XII (hypoglossal), which
innervates the tongue, have been
described as purely motor nerves.

80. MIXED NERVES
- carry both sensory and motor nerve fibers
- cranial nerves V, VII, IX, X are mixed
nerves

81. AUTONOMIC SYSTEM
- The autonomic nervous system may be divided, both functionally
and structurally into sympathetic and parasympathetic nervous
divisions.
1. Sympathetic or Thoracolumbar Divisions of the autonomic
nervous system arises from all the thoracic and the first
three lumbar segments of the spinal cord.
2.Parasympathetic or Craniosacral Divisions of the autonomic
nervous system arises from the third, seventh, ninth, and
tenth cranial nerves and from the second, third, and fourth
sacral segments of the spinal cord.

82. FUNCTIONS OF THE
ANS SYMPATHETIC PARASYMPATHETIC
ORGAN
Eye
Iris Dilates pupil Constricts pupil
Ciliary muscle Flattens lens Bulges lens
Peripheral blood vasoconstriction Vasodilatation
vessels
Salivary glands Stimulates Stimulates serous
viscous ( mucous) secretion
Lacrimal glands None Stimulates
secretion
Sweat glands Copious sweating None

83. FUNCTIONS OF THE
ANS
ORGAN SYMPATHETIC PARASYMPATHETIC
HEART
SA NODE Increased rate Decreased rate
MUSCLE Increased force
of contraction
LUNGS
Bronchi Dilation Constriction
Stomach Dec. motility and Increased motility
Wall tone;
Stimulates secretion of
Glands alkaline juice with low Stimulates secretion
enzyme activity of acid with high enzyme

84. FUNCTIONS OF THE
ANS
ORGAN SYMPATHETIC PARASYMPATHETIC
SUPRARENAL
GLAND
Secretion of None
Medulla
epinephrine
URINARY
BLADDER
Wall Inhibition Excitation
Sphincter Excitation Inhibition
PENIS EJACULATION ERECTION

85. FUNCTIONS OF THE
ANS
ORGAN SYMPATHETIC PARASYMPATHETIC
ARRECTOR PILI
MUSCLES OF HAIR CONTRACTION None
FOLLICLES
ARTERIOLES
Splanchnic CONSTRICTION DILATATION
region and skin

86. Thank you