A complete discussion of fetal development, physiology of the child immediately after birth, and growth and development through the early years of life lies within the province of formal courses in obstetrics and pediatrics. However, many physiological principles are peculiar to the infant, and this chapter discusses the more important of these principles.

1. ANATOMY AND
PHYSIOLOGY OF
NERVOUS SYSTEM
Dr. Muhammad Usman Hashmi
PGT Physiology RMU Rawalpindi

2. INTRODUCTION
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The nervous system is a highly complex
part of an animal that coordinates its
actions and
transmitting
sensory information by
signals to and from
different parts of its body.

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6. Cells of the Nervous System
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7. The nervous system has approximately
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10 million
information
sensory neurons that send
about the internal and
external environment to the brain and
500,000 motor neurons that control the
muscles and glands.

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11. • Ganglia are ovoid structures containing cell bodies of neurons
and glial cells supported by connective tissue. Ganglia function like
relay stations - one nerve enters and an other exits.
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15. ANATOMY OF THE BRAIN
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17. The brain accounts for approximately 2% of
the total body weight; it weighs
approximately 1,400 g in an average young
adult. In the elderly, the average brain weighs
approximately 1,200 g.
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20. •Information transferred includes sensation,
memory, and learned discrimination.
•Right-handed people and some left-handed
people have cerebral dominance on the left
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side of the brain for verbal,
and
linguistic,
analytic
arithmetical, calculating,
functions.
•The non-dominant hemisphere is responsible
for geometric, spatial, visual pattern, and
musical functions.

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25. The basal ganglia are masses of nuclei located deep
in the cerebral hemispheres.
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28. The thalamus lies on either side of the
third ventricle and acts primarily as a relay
station for all sensation except smell. All
memory, sensation, and pain impulses also
pass through this section of the brain.
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29. •The hypothalamus is located anterior and
inferior to the thalamus. The
hypothalamus lies immediately beneath
and lateral to the lower portion of the
wall of the third ventricle.
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30. •It includes the optic chiasm (the point at which
the two optic tracts cross) and the mamillary
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emotional response
bodies (involved in olfactory
to
reflexes and
odors). The
infundibulum of the hypothalamus connects it
to the posterior pituitary gland.

31. •Plays an important role in the endocrine
system because it regulates the pituitary
secretion of hormones that influence
metabolism, reproduction, stress
response, and urine production.
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32. by promoting
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•Maintain fluid balance
•Maintains temperature regulation
vasoconstriction or vasodilatation
•Site of the hunger center and is involved in appetite
control

33. •Centers for regulating the sleep–wake cycle,
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blood pressure, aggressive and
behavior, and emotional responses
sexual
(i.e.,
blushing, rage, depression, panic, and fear)
•Controls and regulates the autonomic nervous
system

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37. •Nerve fibers from all portions of the cortex
converge in each hemisphere and exit in the
form of a tight bundle of nerve fibers known as
the internal capsule.
•Having entered the pons and the medulla, each
bundle crosses to the corresponding bundle from
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40. •The midbrain connects the pons and the
cerebellum with the cerebral hemispheres; it
contains sensory and motor pathways and
serves as the center for auditory and visual
reflexes. Cranial nerves III and IV originate in
the midbrain.
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41. •The pons is situated in front of the cerebellum
between the midbrain and the medulla and is a
bridge between the two halves of the cerebellum,
and between the medulla and the cerebrum. Cranial
nerves V to VIII connect to the brain in the pons. The
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Portions of the
pons contains motor
pons
and sensory pathways.
also control the heart,
respiration, and blood pressure.

42. • The medulla oblongata contains motor fibers from the brain to
the spinal cord and sensory fibers from the spinal cord to the
brain. Most of these fibers cross, or decussate, at this level.
Cranial nerves IX through XII connect to the brain in the
medulla.
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44. •The cerebellum is separated from the cerebral
hemispheres by a fold of dura mater, the tentorium
cerebelli. The cerebellum has both
inhibitory actions and is largely
coordination of movement. It also controls
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excitatory and
responsible for
fine
movement, balance, position sense (awareness of where
each part of the body is), and integration of sensory
input.

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46. Structures protecting the brain
The meninges (fibrous connective tissues that cover the brain and spinal cord)
provide protection, support, and nourishment to the brain and spinal cord.
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49. Dura mater
•It is the outermost layer and covers the
brain and the spinal cord. It is tough,
thick, inelastic, fibrous, and gray.
•There are four extensions of the dura:
The falx cerebri, which separates the
two hemispheres in a longitudinal
plane.
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50. The tentorium, which is an infolding of the
dura that forms a tough membranous shelf.
The falx cerebelli, which is between the
two lateral lobes of the cerebellum.
The diaphragm sellae, which provides a
“roof” for the sella turcica.
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51. • When excess pressure occurs in the cranial cavity, brain tissue may be
compressed against the tentorium or displaced downward, a process
called herniation.
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52. •Arachnoid
It is the middle membrane; an extremely thin, delicate
membrane that closely resembles a spider web (hence the
name arachnoid). It appears white because it has no blood
supply.
The arachnoid layer contains the choroid plexus, which is
responsible for the production of cerebrospinal fluid (CSF).
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53. •This membrane also has unique fingerlike projections,
arachnoid villi, that absorb CSF.
•In the normal adult, approximately 500 mL of CSF is
produced each day but 125 to 150 mL is absorbed by
the villi.
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55. •When blood enters the system (from trauma or
haemorrhagic stroke), the villi become obstructed and
hydrocephalus (increased size of ventricles) may result.
•Pia mater—It is the innermost membrane; a thin,
transparent layer that lies closely to brain and extends
into every fold of the brain’s surface.
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56. Cerebrospinal fluid
• Clear and colorless fluid with a specific gravity of 1.007
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58. •The ventricular and subarachnoid system contains
approximately 125 to 150 mL of fluid, while 15 to 25
mL of CSF is located in each lateral ventricle.
•The composition of CSF is similar to other extracellular
fluids (such as blood plasma), but the concentrations
of the various constituents are different.
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59. •The analysis and laboratory report of CSF usually
contains information on color, specific gravity, protein
count, white blood cell count, glucose, and other
electrolyte levels; it may also be tested for
immunoglobulins or lactate.
•Normal CSF contains a minimal number of white blood
cells and no red blood cells.
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60. Cerebral circulation
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•The cerebral circulation receives approximately 15% of
the cardiac output. The brain does not store nutrients
and has a high metabolic demand that requires the
high blood flow.

61. •In contrast to other organs that may tolerate
decreases in blood flow because of their adequate
collateral circulation, the brain lacks additional
collateral blood flow, which may result in irreversible
tissue damage when blood flow is occluded for even
short periods of time.
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64. veins and
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Cerebral
sinuses are unique
because, unlike other
the body,
not have
veins in
they do
valves to
blood from
backward
depend
prevent
flowing
and
on both
and blood
gravity
pressure.

65. Blood–brain barrier
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• The CNS is inaccessible to many substances that circulate in the
blood plasma (e.g., dyes, medications, and antibiotics). After
being injected into the blood, many substances cannot reach the
neurons of the CNS because of the blood–brain barrier. This
barrier is formed by the endothelial cells of the brain’s capillaries,
which form continuous tight junctions, creating a barrier to
macromolecules and many compounds.

66. •All substances entering the CSF must filter through
the capillary endothelial cells and astrocytes. Often
altered by trauma, cerebral oedema, and cerebral
hypoxemia, the blood–brain barrier has implications
in the treatment and selection of medication for CNS
disorders as well as serving a protective function.
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68. • Brain waves are
rhythmic
fluctuation of
electric potential
between parts of
the brain as seen
on an
electroencephalo
gram (EEG). To
measure brain
waves electrodes
are placed
the scalp
onto
using
the EEG.
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69. Anatomy of the spinal cord
•Approximately 45 cm (18 in)
long and about the 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.
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70. • Continuing below the second lumbar space are the nerve roots
that extend beyond the conus, which are called the cauda
equina because they resemble a horse’s tail. Similar to the
brain, the spinal cord consists of gray and white matter.
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74. Vertebral Column
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The vertebrae
are separated
by disks,
except for the
and
first
second
cervical, the
sacral, and the
coccygeal
vertebrae.

77. THE PERIPHERAL NERVOUS
SYSTEM
The peripheral nervous system includes
the cranial nerves, the spinal nerves, and
the autonomic nervous system.
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79. Three are
entirely sensory
(I, II, VIII), five
VI, XI,
and
mixed
are motor (III,
IV, and
XII), four
are (V,
VII, IX, and X) as
they have both
and
sensory
motor
functions.
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80. SPINAL NERVES
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81. AUTONOMIC NERVOUS SYSTEM
•The autonomic nervous system 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.
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83. •Sympathetic stimuli are mediated by nor-epinephrine and
parasympathetic impulses are mediated by acetylcholine.
•Sympathetic neurons are located in the thoracic and the
lumbar segments of the spinal cord; their axons, or the pre-
ganglionic fibers, emerge by way of anterior nerve roots
from the eighth cervical or first thoracic segment to the
second or third lumbar segment.
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84. Sympathetic Syndromes
•Dilation of the pupil of the eye on the same side as a
penetrating wound of the neck (evidence of disturbance of
the cervical sympathetic cord)
•Temporary paralysis of the bowel (indicated by the
absence of peristaltic waves and the distention of the
intestine by gas) after fracture of any one of the lower
dorsal or upper lumbar vertebrae with hemorrhage into
the base of the mesentery
•Marked variations in pulse rate and rhythm that often
follow compression fractures of the upper six thoracic
vertebrae.
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85. MOTOR SYSTEM FUNCTION
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Cortical
homunculus
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88. •Coordination of Movement. The smoothness,
accuracy, and strength that characterize the
muscular movements of a normal person are
attributable to the influence of the
cerebellum and the basal ganglia.
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89. SENSORY SYSTEM FUNCTION
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Integrating Sensory Impulses
• The thalamus integrates all sensory impulses except
olfaction. It plays a role in the conscious awareness of pain
and the recognition of variation in temperature and touch.
The thalamus is responsible for the sense of movement and
position and the ability to recognize the size, shape, and
quality of objects.

90. Receiving Sensory Impulses
• Afferent impulses travel from their points of origin to their
destinations in the cerebral cortex via the ascending pathways
directly, or they may cross at the level of the spinal cord or in
the medulla, depending on the type of sensation that is
registered. Sensory information may be integrated at the level
of the spinal cord or may be relayed to the brain.
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91. Sensory Losses
• Destruction of a sensory nerve results in total loss of sensation in
its area of distribution. Transection of the spinal cord yields
complete anesthesia below the level of injury. Selective destruction
or degeneration of the posterior columns of the spinal cord is
responsible for a loss of position and vibratory sense in segments
distal to the lesion, without loss of touch, pain, or temperature
perception.
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92. CONCLUSION
• As discussed throughout the presentation, learning about anatomy
and physiology of brain and spinal cord will help nurses to
understand the functioning of nervous system and various
neurological disorders.
• Nurses can do neurological assessment of patients, observe the
sign and symptoms, provide the necessary nursing care, prevent
mplications and support the patient psychologically.
an
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93. REFERENCES
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4.B D Chaurasia. HUMAN ANATOMY Regional and applied dissection and
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449.

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