This document provides an overview of the nervous system including its anatomy and physiology. It discusses the central nervous system including the brain, spinal cord and meninges. It describes the peripheral nervous system including cranial nerves and autonomic nervous system. Key cells, structures and functions are defined including neurons, glial cells, neurotransmitters, blood brain barrier and cerebrospinal fluid.
1. MEDICAL SURGICAL NURSING - II:
Nursing management of patients
with neurological disorders
REVIEW OF ANATOMY & PHYSIOLOGY
BY
K.SIVASANKARI
ASSISTANT PROFESSOR
MCON
2. OBJECTIVES
• To understand about the parts of nervous system
• To enumerate the functions of nervous system
• To perceive about cranial nerve function
• To recognize sympathetic & parasympathetic
nerves & its function
• To utilize the critical thinking & nursing process
approach during the assessment of neurological
system
5. INTRODUCTION
• Nervous system consists of two major parts
• Central nervous system – brain & spinal cord
• Peripheral nervous system – cranial nerves,
spinal nerves & autonomic nervous system
6. Function of nervous system
• To control motor, sensory, autonomic,
cognitive & behavioural activities
• Brain contains more than 100 billion cells links
the motor and sensory pathways
• Monitor the body’s processes
7. Contd..
• Respond to internal & external environment
• Maintain homeostasis
• Directs all psychological, biological & physical
activity through complex chemical & electrical
messages
11. CELLS OF NERVOUS SYSTEM
• Basic functional unit of the brain is
NEURON
• Parts – dendrites, cell body and axon
• Neurons are supported, protected &
nourished by glial cells which are 50 times
greater in number than neurons
12. DENDRITES CELL BODY AXON
Branch type
structures for
receiving
electrochemical
messages
•Occurring in
clusters are
called ganglia or
neuclei
•Clusters of cell
bodies with
same function is
called a center
(eg. Resp center)
•Long projection
that carries
electrical
impulses away
from the cell
body
•Some axons
have myelinated
sheath that
increases speed
of conduction
14. NEUROTRANSMITTERS
• Communicate messages from one neuron
to another or from a neuron to target cell
such as muscle or endocrine cells
• These are manufactured and stored in
synaptic vesicles
15. Contd..
• As an electrical action potential moves along
the axon & reaches the nerve terminal,
neurotransmitters are released into the
synapse
• A neurotransmitter can either excite or inhibit
activity of target cell
21. MAJOR NEUROTRANSMITTERS
NEURO
TRANSMITTER
SOURCE ACTION
ACETYLCHOLINE Many areas of the brain,
autonomic nervous
system
Usually excitatory;
parasympathetic effects
sometimes inhibitory
(stimulation of heart by
vagal nerve)
SEROTONIN Brainstem,
hypothalamus, dorsal
horn of the spinal cord
Inhibitory, helps control
mood & sleep, inhibits
pain pathways
DOPAMINE Substantia nigra & basal
ganglia
Usually inhibitory, affects
behaviour (attention,
emotions) & fine
movements
22. NEURO
TRANSMITTER
SOURCE ACTION
NOR EPINEPHRINE (major
transmitters of the
sympathetic nervous
system)
Brain stem,
hypothalamus,
postganglionic neurons of
the sympathetic nervous
system
Usually excitatory, affects
mood & overall activity
GAMMA AMINO BUTYRIC
ACID
Spinal cord, cerebellum,
basal ganglia, some
cortical areas
Inhibitory
ENKEPHALIN, ENDORPHIN Nerve terminals in the
spine, brain stem,
thalamus &
hypothalamus, pituitary
gland
Excitatory, pleasurable
sensation, inhibits pain
transmission
23. CENTRAL NERVOUS SYSTEM
• Brain composed of 2% of total body weight in
an average adult
• Weight of the brain is 1400 gm approximately
in an adult
• Brain is divided into three major areas
– Cerebrum
– Brain stem
– Cerebellum
25. CEREBRUM – Contd..
• Outside surface the cerebrum has many
folded layers called gyri which increases
the surface area of brain
• Between each gyrus there is sulcus
• The two hemispheres are joined at the
lower portion of the fissure by the corpus
callosum
26. Contd..
• The external and outer portion of
hemispheres is made up of grey matter
approximately 2 to 5 mm in depth; it contains
billions of neuron cell bodies, giving it a grey
appearance
27. Contd..
• White matter makes up the innermost layer &
is composed of myelinated nerve fibers &
neuraglia cells that form tracts or pathways
connecting various parts of the brain with one
another
• Cerebral hemispheres are divided into pairs of
lobes as follows
28. Contd..
• Frontal lobe:
– Largest lobe
– Functions – concentration, abstract thought,
information storage, or memory and motor
function
– Contain Broca’s area which is located in left
hemisphere & is critical for motor control of
speech
– Responsible for large part for a person’s affect,
judgement, personality & inhibitions
29. Contd..
• Parietal lobe:
– Predominantly sensory lobe
– Located posterior to frontal lobe
– Functions – analysis sensory information & relays
the interpretation of this information to other
critical areas and is essential to a person’s
awareness of body position in space, size & shape
discrimination & right and left orientation
30. Contd..
• Temporal lobe:
– Located inferior to frontal and parietal lobe
– Functions – contains auditory receptive areas &
plays a role in memory of sound & understanding
of language & music
31. Contd..
• Occipital lobe:
– Located posterior to parietal lobe
– Functions – responsible for visual interpretation &
memory
32. Corpus callosum
It is a thick collection of nerve fibers
Responsible for transmission of information from
one side of brain to other
Information transferred includes sensation, memory
& learned discrimination
33. Contd..
Right handed & some left handed people have
cerebral dominance on the left side of the brain
for verbal, linguistic, arithmetic, calculation &
analytic functions
Non dominant hemisphere is responsible for
geometric, spatial, visual, pattern and musical
functions
35. Thalami:
– Lie on either side of the 3rd ventricle & act
primarily as a relay station for all sensation except
smell
– All memory, sensation & pain impulses pass
through this section of brain
36.
37. Hypothalamus:
–Located anterior & inferior to the thalamus,
and beneath & lateral to the 3rd ventricle
–The infundibulum of hypothalamus connects
it to the posterior pituitary gland
–It plays important role in endocrine system
because it regulates pituitary secretion of
hormones
38. Contd..
– Thermoregulation, site of hunger, regulate sleep
wake cycle, BP, aggressive & sexual behaviour &
emotional responses also control autonomic
nervous system
– Optic chaism & mamillary bodies bodies
(olfaction) are also found in this area
39. Basal ganglia
• Mass of neuclei located deep in the cerebral
hemispheres that are responsible for control
of fine motor movements, including those of
hands & lower extrimities
41. Midbrain
• Connects the pons and cerebrum with the
cerebral hemispheres
• It contains sensory and motor pathways
• Centre for auditory & visual reflexes
• Cranial nerve III and IV originate in the
midbrain
42. Pons
• Pons is situated in front of the cerebellum
between midbrain and medulla and is a bridge
between two halves of cerebellum and
between medulla and midbrain
• Cranial nerves V through VIII originate in pons
• Also contains motor and sensory pathways
• Portion of pons helps to regulate respiration
43. Medulla oblongata
• Motor fiber from brain to spinal cord &
sensory fiber from spinal cord to brain are
located in the medulla
• Cranial nerves IX through XII originates in
medulla
44. Contd..
• Reflex center for respiration, BP, Heart rate,
coughing, vomiting, swallowing & sneezing are
also located in the medulla
• The reticular formation responsible for arousal
& the sleep wake cycle begins in the medulla
& connects with numerous higher structures
45. CEREBELLUM
• It is posterior to the midbrain and pons, and
below the occipital lobe
• It integrates sensory information to provide
smooth coordinated movement
• It controls fine movement, balance, and
position (postural) sense or proprioception
(awareness of position of body parts without
looking at them)
46. STRUCTURES PROTECTING THE BRAIN
• Contained in rigid skull – protects from injury
• Major bones of skull – frontal, parietal,
temporal, occipital, and sphenoid bones
• These bones join at the suture lines and form
the base of the skull
• Indentations in the skull base are known as
fossae
47. Contd..
• Anterior fossa contains frontal lobe, middle
fossa contains temporal lobe, posterior fossa
contains cerebellum & brain stem
• The meninges (fibrous connective tissues that
cover the brain & spinal cord) provide
*protection, *support, and *nourishment
• The layers of meninges are the dura mater,
arachnoid, and pia mater
48.
49. Dura mater
• Outermost layer, covers the brain and the spinal
cord
• Tough, thick, inelastic, fibrous and gray
• 3 major extensions
falx cerebri (folds b/w two hemispheres)
tentorium (folds b/w occipital lobe and
cerebellum)
falx cerebelli (located b/w left & right side of
cerebellum)
50. Dura mater – clinical significance
• When excess pressure occurs in cranial cavity,
brain tissue may be compressed against these
dural folds or displaced around them – a
process called herniation
• Space b/w dura mater and skull and space b/w
periosteum and the dura in the vertebral
column known as epidural space
51. Contd..
• Potential space exists below the dura called
subdural space – blood or abscess can
accumulate in these potential spaces
52. Arachnoid
• Middle membrane; an extremely thin,
delicate membrane that closely resembles
a spider web
• This membrane has CSF in the space below
it known as subarachnoid space
53. Contd..
• This membrane has arachnoid villi, which are
unique finger like projections that absorb CSF
into the venous system
• When blood or bacteria enter the
subarachnoid space, the villi become
obstructed and communicating hydrocephalus
(increased size of ventricles) may result
54. Pia mater
• The innermost, thin, trasperent layer that
hugs the brain closely and extends into every
fold of the brain’s surface
55. Cerebrospinal fluid
• It is a clear and colourless fluid
• Produced in the choroid plexus of the
ventricles and circulates around the
surface of the brain & the spinal cord
• Totally 4 ventricles – right & left & 3rd &
4th
• The two lateral ventricles open into 3rd
ventricle at the interventricular
foramen (foramen of Monro)
56. Contd..
• The 3rd & 4th ventricles connect via the
aqueduct of Sylvius
• The 4th ventricle drains CSF into subarachnoid
space on the surface of brain & spinal cord,
where it is absorbed by the arachnoid villi
• Blockage of flow of CSF anywhere in the
ventricular system produces obstructive
hydrocepalus
57. CSF – contd..
• It is vital in immune & metabolic function
• Produced at teh rate of about 500 mL/day
• Ventricles & subarachnoid space contain
approximately 150 mL of fluid
• The composition of CSF is same like other ECF
but concentration differs. Normal CSF contains
a minimal amount of white blood cells and no
red blood cells
61. Cerebral circulation
• Brain does not store any nutrients and
requires a constant supply of oxygen
• These needs are met through cerebral
circulation
• Brian receives approximately 15% of
cardiac output or 750 mL/min of blood
flow
62. Contd..
• Brain circulation are unique in several aspects –
1st arterial & venous vessels are not parellel due
to venous system plays role in CSF absorption,
• 2nd brain has collateral circulation through circle
of willis, allowing blood flow to be redirected on
demand,
• 3rd blood vessels in the brain have two rather
than three layers, which may make them more
prone to rupture when weakened or under
pressure
63. Arteries
• Common carotid artery (1st bifurcation off the
aorta) supplies to the anterior brain
• Internal carotid arteries arise at the
bifurcation of the common carotid
• Branches of the internal carotid arteries
(anterior & middle cerebral arteries) and their
connections (anterior & posterior
communicating arteries) form the Circle of
Willis
65. Arteries - contd..
• Vertebral arteries (branch from the subclavian
arteries) supplies most of the posterior
circulation of the brain
• At the level of brain stem, vertebral arteries
join to form basilar artery
• Basilar artery divides to form two branches of
posterior cerebral artery
66. Arteries - applied anatomy
• Functionally, the posterior and anterior portions
of the circulation usually remain separate
• However, the Circle of Willis can provide
collateral circulation through communicating
arteries if one vessel occluded or ligated
67. Contd..
• Bifurcations along the circle of Willis are
frequent sites of aneurysm formation.
Aneurysms are out-pouchings of blood vessel
due to vessel wall weakness. Aneurysms may
rupture & cause hemorrhagic shock
68. Veins
• Venous drainage for the brain does not
follow the arterial circulation as in other
body structures
• The veins reach the brain’s surface, join
larger veins, & then cross the subarachnoid
space & empty into the dural sinuses, which
are the vascular channels embedded in the
dura
69. Contd..
• The network of the sinuses carries venous
outflow from the brain & empties into the
internal jugular veins, returning the blood to
the heart
• Cerebral veins are unique because they do not
have valves to prevent blood from flowing
backward and depend on both gravity & BP
for flow
70. Blood- Brain Barrier (BBB)
• CNS is inaccessible to many substances that
circulate in the blood plasma (e.g dyes,
medications & antibiotic agents) because of
the BBB
• It is formed by endothelial cells of brain’s
capillaries, which form continuous tight
junctions, creating a barrier to
macromolecules & many compounds
71. Contd..
• All substances entering the CSF must filter
through the capillary endothelial cells &
astrocytes
• BBB has a protective function but can be
altered by trauma, cerebral edema & cerebral
hypoxemia – which has impact on treatment
& selection of medication for CNS disorder
72.
73. The spinal cord
• It is continuous with the medulla, extending
from the cerebral hemispheres and serving
as the connection between the brain and
the periphery
• Approximately 45 cm (18 inches) long and
about thickness of a finger, it extends from
the foramen magnum at the base of the
skull to the lower border of the first lumbar
vertebra, where it tapers to a fibrous band
called the conus medullaris
74. Contd..
• Continuing below the second lumbar space
are the nerve roots that extend beyond the
conus, called cauda equina (horse’s tail)
• Meninges surround the spinal cord
75. The spinal cord – contd..
• In a cross-sectional view, the spinal cord has
H-shaped central core of nerve cell bodies
(gray matter) surrounded by ascending &
descending tracts (white matter)
• The lower portion of H is broader than the
upper portion & corresponds to the anterior
horns
76. Contd..
• The anterior horn contain cells with fibers that
form the anterior (motor) root & are essential
for the voluntary & reflex activity of the
muscles they innervate
• The thinner posterior (upper horns) portion
contains cells with fibers that enter over the
posterior (sensory) root & thus serve as a
relay station in the sensory/reflex pathway
77. The spinal cord – Contd..
• The thoracic region of the spinal cord has a
projection from each side at the crossbar of H-
shaped structure of gray matter called the
lateral horn
• It contain the cells that give rise to the
autonomic fibers of the sympathetic division.
The fibers leave the spinal cord through the
anterior roots in the thoracic & upper lumbar
segments
78.
79. The spinal tracts
• White matter of the spinal cord is composed
of myelinated and unmyelinated nerve fibers
– fast conducting myelinated fibers form
bundles (bundles with common function
called tracts)
• There are six ascending tracts
80. Contd..
• Two tracts, known as the fasciculus cuneatus
& gracilis or the posterior columns, conduct
sensation of deep touch, pressure, vibration,
position, and passive motion from same side
of the body
• Before reaching cerebral cortex, these fibers
cross to the opposite side in the medulla
82. The spinal tracts-contd..
• The anterior and posterior spinocerebellar
tracts conduct sensory impulses from muscle
spindles, providing necessary input for
coordinated muscle contraction.They ascend
uncrossed & terminate in the cerebellum
83. Contd..
• The anterior & lateral spinothalamic tracts are
responsible for conduction of pain,
temperature, proprioception, fine touch, and
vibratory sense from the upper body to the
brain
• They cross to the opposite side of the cord
and then ascend to the brain, terminating in
the thalamus
85. The spinal tracts-contd..
• There are eight descending tracts. The
anterior & lateral corticospinal tracts
conduct motor impulses to the anterior
horn cells from the opposite side of the
brain, cross in the medulla, and control
voluntary muscle activity
• The three vestibulospinal tracts descend
uncrossed and are involved in some
autonomic functions (sweating, pupil
dilatation & circulation) & involuntary
muscle control
86. Contd..
• The corticobulbar tract conducts impulses
responsible for voluntary head & facial muscle
movement & crosses at the level of the brain
stem.
• The rubrospinal & reticulospinal tracts
conduct impulses involved with involuntary
muscle movement
88. Vertebral column
• The bones of the vertebral column
surround & protect the spinal cord &
normally consist of 7 cervical, 12
thoracic, and 5 lumbar vertebrae, as
well as the sacrum (a fused mass of 5
vertebrae), and terminate in the coccyx
• Nerve roots exit from the vertebral
column through the intervertebral
foramina
89. Contd..
• The vertebrae are separated by disks, except for
the first and second cervical, the sacral and the
coccygeal vertebrae
• Each vertebrae has a ventral solid body & a dorsal
segment (arch), which is posterior to the body
• The arch is composed of two pedicles & two
laminae supporting seven processes
• The vertebral body, arch, pedicles, and laminae
all encase & protect the spinal cord
90.
91. The peripheral nervous system
• It includes,
• cranial nerves,
• the spinal nerves, and
• autonomic nervous system
92. Cranial nerves
• Twelve pairs of cranial nerves emerge from
the lower surface of the brain and pass
through openings in the base of the skull
• Three cranial nerves are entirely sensory (I,II
and VIII), five are motor (III,IV,VI,XI, and XII),
and four are mixed sensory and motor
(V,VII,IX, and X) – S2M2XMXSX2M2
93. Contd..
• The cranial nerves are numbered in order in
which they arise from the brain
• The cranial nerves innervate the head, neck,
and special sense structures
94.
95. Cranial nerves
Cranial nerve Type Function
I (olfactory) Sensory Sense of smell
II (optic) Sensory Visual acuity and visual fields
III (oculomotor) Motor Muscles that move the eye and
lid, pupillary constriction, lens
accommodation
IV (trochlear) Motor Muscles that move the eye
V (trigeminal) Mixed Facial sensation, corneal reflex,
mastication
VI (abducens) Motor Muscles that move the eye
96. Cranial nerve Type Function
VII (Facial) Mixed Symmetry of facial expression and
muscle movement in upper and
lower face, salivation and tearing,
taste, sensation in the ear
VIII (Acoustic/
vestibulocochlear)
Sensory Hearing & equilibrium
IX
(Glossopharyngeal)
Mixed Taste, sensation in pharynx and
tongue, pharyngeal muscles,
swallowing
97. X (vagus) Mixed Muscles of pharynx, larynx, &
soft palate, sensation in external
ear, pharynx, larynx, thoracic and
abdominal viscera,
parasympathetic innervation of
thoracic and abdominal organs
XI (Spinal
Accessory)
Motor Sternocleidomastoid and
trapezius muscles
XII (hypoglossal) Motor Movement of the tongue
98. Spinal nerves
• The spinal cord is composed of 31 pairs of spinal
nerves
• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral and
• 1 coccygeal
• Each spinal nerve has ventral root & dorsal root
99.
100. Spinal nerves – contd..
• The dorsal roots are sensory and transmit
sensory impulses from specific areas of the
body known as dermatomes to the dorsal
horn ganglia
• The sensory fiber may be somatic, carrying
information about pain, temperature, touch,
and position sense (proprioception) from the
tendons, joints, and body surfaces; or visceral,
carrying information from the internal organs
101. Contd..
• The ventral roots are motor & transmit
impulses from the spinal cord to the body;
these fibers are also either somatic or visceral
• The visceral fibers include autonomic fibers
that control the cardiac muscles and glandular
secretions
102. Autonomic nervous system
• It regulates the activities of internal organs
such as the heart, lungs, blood vessels,
digestive organs, and glands
• Maintenance and restoration of internal
homeostasis is largely the responsibility of the
autonomic nervous system
103. Contd..
• Two major divisions – sympathetic nervous
system (mostly excitatory response – ‘fight-or-
flight’) and parasympathetic nervous system
(controls mostly visceral function)
104. Effects of autonomic nervous system
Structure or activity Parasympath
etic effects
Sympathet
ic effects
Pupil of the eye constricted Dilated
Circulatory system
• rate & force of
heart beat
Decreased Increased
114. Motor & sensory pathways of nervous
system
• Motor pathways
• The corticospinal tract begins in the motor
cortex, a vertical band within each frontal
lobe, and controls voluntary movements of
the body
• The exact locations within the brain at which
the voluntary movements of the muscles of
the face, thumb, hand, arm, trunk, and leg
originate are known
115. Motor pathways – contd..
• Upper & lower motor neurons
• Upper motor neurons travel in several neural
pathways through the central nervous system
(CNS)
116. Tract Pathway Function
corticospinal
tract
from the motor cortex
to lower motor
neurons in the ventral
horn of the spinal
cord
The major function of this
pathway is fine voluntary
motor control of the
limbs. The pathway also
controls voluntary body
posture adjustments.
corticobulbar
tract
from the motor cortex
to several nuclei in
the pons and medulla
oblongata
Involved in control of
facial and jaw
musculature, swallowing
and tongue movements.
colliculospinal
tract
(tectospinal
tract)
from the superior
colliculus to lower
motor neurons
Involved in involuntary
adjustment of head
position in response to
visual information.
117. rubrospinal
tract
from red nucleus
to lower motor
neurons
Involved in
involuntary
adjustment of arm
position in response
to balance
information; support
of the body.
vestibulospina
l tract
from vestibular
nuclei, which
processes stimuli
from semicircular
canals
It is responsible for
adjusting posture to
maintain balance.
reticulospinal
tract
from reticular
formation
Regulates various
involuntary motor
activities and assists
in balance.
118. Lower motor neurons (LMNs) are motor
neurons located in either the anterior grey
column, anterior nerve roots (spinal lower
motor neurons)
Classification
• Lower motor neurons are classified based on
the type of muscle fiber they innervate:
• Alpha motor neurons (α-MNs) innervate
extrafusal muscle fibers, the most numerous
type of muscle fiber and the one involved in
muscle contraction.
119. Contd..
• Beta motor neurons (β-MNs) innervate
intrafusal fibers of muscle spindles with
collaterals to extrafusal fibers (type of slow
twitch fibers).
• Gamma motor neurons (γ-MNs) innervate
intrafusal muscle fibers, which together with
sensory afferents compose muscle spindles.
120.
121. Clinical significance
• Damage to lower motor neurons, lower
motor neuron lesions (LMNL) cause muscle
wasting, decreased strength and decreased
reflexes in affected areas. Damage to the
upper motor neuron causes muscle atrophy
with long standing lesion.
122. Contd..
• These findings are in contrast to findings in
upper motor neuron lesions. LMNL is
indicated by abnormal EMG potentials,
fasciculations, paralysis, weakening of
muscles, and neurogenic atrophy of skeletal
muscle. Bell's Palsy, Bulbar palsy, Poliomyelitis
and Amyotrophic lateral sclerosis (ALS) are all
pathologies associated with lower motor
neuron dysfunction.
123. Sensory system function
• The sensory nervous system is a part of the
nervous system responsible for processing
sensory information. A sensory system
consists of sensory neurons (including the
sensory receptor cells), neural pathways, and
parts of the brain involved in sensory
perception.
124. Contd..
• Commonly recognized sensory systems are
those for vision, hearing, touch, taste, smell,
and balance. In short, senses are transducers
from the physical world to the realm of the
mind where we interpret the information,
creating our perception of the world around
us.
125. Human sensory system
• The human sensory system consists of the
following subsystems:
• Visual system
• Auditory system
126. Contd..
• Somatosensory system consists of the
receptors, transmitters (pathways) leading to
S1, and S1 that experiences the sensations
labelled as touch or pressure, temperature
(warm or cold), pain (including itch and tickle),
and the sensations of muscle movement and
joint position including posture, movement,
and facial expression (collectively also called
proprioception)
