The Nervous System
By WILLIAM M. BANAAG, R.N.
The Nervous System
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The Nervous System is the
master controlling and
communicating system of the
body.
The Nervous System
CONTROLS and
COORDINATES ALL
ESSENTIAL FUNCTIONS of the
Human Body.
Function of the Nervous System
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SENSORY FUNCTION:
Nervous system uses its millions of
sensory receptors to monitor changes occurring both inside and
outside of the body. Those changes are called STIMULI, and the
gathered information is called Sensory Input.
INTEGRATIVE FUNCTION: The Nervous System process and
interprets the sensory input ad makes decisions about what should
be done at each moment—a process called Integration.
MOTOR FUNCTION:
The Nervous System then sends
information to muscles, glands, and organs (effectors) so they can
respond correctly, such as muscular contraction or glandular
secretions.
Structural Classification of the Nervous
System:
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Central Nervous System (CNS):
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Consists of the brain and the spinal cord, which act
as the integrating and command centers of the
nervous system.
They interpret incoming sensory information and
issue instructions based on past experience and
current conditions.
Peripheral Nervous System (PNS):
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It is the part of the nervous system outside the
CNS.
They link all parts of the body by carrying impulses
from the sensory receptors to the CNS and from
the CNS to the appropriate glands or muscles.
It consists mainly of the nerves that extend from
the brain and spinal cord.
Cranial Nerves carry impulses to and from the
brain.
Spinal Nerves carry impulses to and from the spinal
cord.
Central Nervous system (CNS)
THE BRAIN
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The brain is located within
the cranial cavity of the
skull and consists of the
cerebral hemispheres,
diencephalon, brain stem,
and cerebellum.
Central Nervous system (CNS)
THE BRAIN
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Cerebral Hemispheres:
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The two cerebral hemispheres (the left and the right
side) form the largest apart of the brain, called the
cerebrum
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Its surface, called cerebral cortex, is convoluted
and exhibits elevated ridges called gyri, which are
separated by shallow grooves called sulci. It also
has deeper grooves called fissures, which separate
large regions of the brain.
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Each cerebral hemisphere is divided by some fissures
and sulci into a number of lobes which are named for
the cranial bones that lie over them.
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The cerebral hemispheres are involved in logical
reasoning, moral conduct, emotional responses,
sensory interpretation, and the initiation of voluntary
muscle activity.
sulc
i
fissur
e
gyri
Point to Remember…
“Pathways of nerve impulses are crossed pathways — meaning that the Left side of the
brain controls the RIGHT side of the body, and the Right side of the brain controls
the LEFT side of the body.”
Functional Areas of the Cerebral
Hemispheres
The cerebral hemispheres has three (3) types of functional
areas…
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Sensory areas
Motor areas
Association areas
Functional Areas of the Cerebral
Hemispheres
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Sensory Areas:
receive
and interpret sensory impulses
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Primary somatosensory area
(Areas 1, 2 & 3) - receives
impulses from somatic sensory
receptors for touch, pain, and
temperature.
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Primary visual area (Area 17) –
receives visual input concerning
shape, color, and movement.
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Primary auditory area (Area 41
& 42) – interprets the basic
characteristics of sounds such as
pitch and rhythm.
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Primary gustatory area (Area
43) – receives impulses related to
taste.
Functional Areas of the Cerebral
Hemispheres
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Motor Areas:
control muscular movement
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Primary motor area (Area 4) –
controls voluntary contractions of
specific muscles or group of
muscles on the opposite side of
the body (e.g. finger maneuver)
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Motor speech area or Brocha’s
area (Area 44) – involves in the
translation of thoughts into
speech.
▪ It is located in only one cerebral
hemisphere (usually the left).
▪ Damage to this area causes inability
to say words properly—you know
what you want to say, but you can’t
vocalize the word.
Functional Areas of the Cerebral
Hemispheres
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Association Areas: deal with
more complex, integrative functions
such as memory, emotions,
reasoning, will, judgement,
personality traits, and intelligence.
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Somatosensory association area
(Areas 5 & 7)
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Its role is to integrate and interpret
sensations
It permits you to: determine the exact
shape and texture of an object without
looking at it; determine the orientation
of one object to another as they are
felt; sense the relationship of one body
part to another.
It stores memories of past sensory
experiences—thus you can compare
sensations with previous experiences.
Visual association area (Areas 18 &
19) – it relates present to past visual
experiences with recognition and
evaluation of what is seen.
Functional Areas of the Cerebral
Hemispheres
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Premotor area (Area 6)
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Frontal eye field area (Areas 8) – it
controls voluntary scanning movements of
the eyes—like for instance, searching for
a word in a dictionary.
Auditory association (Wernicke’s) area
(Area 22)
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It deals with learned motor activities of a
complex and sequential nature, for example,
to write a word.
It controls learned skilled movements and
serves as a memory bank for such movements.
It determines if a sound is a speech, music, or
noise;
It also interprets the meaning of speech by
translating words into thoughts.
Gnostic (gnosis = knowledge) area (Areas
5, 7, 39 & 40)
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It integrates sensory interpretations from
the association areas and impulses from other
areas so that a common thought can be
formed from the various sensory inputs.
It then transmits signals to other parts of
the brain to cause the appropriate response
to the sensory signal.
Brain Lateralization
On gross examination, the brain appears the same on both sides, however
there are functional differences…
RIGHT HEMISPHERE
LEFT HEMISPHERE
Right side control
Spoken and written
language
◼ Numerical and
scientific skills
◼ Reasoning
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Left side control
Musical and artistic
awareness
Space and pattern
perception
Insight
Imagination
Generating mental
images to compare
spatial relationship
Look at the chart and say the COLOR not the word.
YELLOW BLUE ORANGE
BLACK RED GREEN
PURPLE YELLOW RED
ORANGE GREEN BLACK
MAGENTA CYAN BROWN
PINK
Left – Right Conflict
Your right brain tries to say the color but your left brain insists on
reading the word.
Memory
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Memory is the storage and retrieval of information
Stages of Memory
•Short-term memory (STM, or working memory) – a fleeting memory of the
events that continually happen
✓STM lasts seconds to hours and is limited to 7 or 8 pieces of information
•Long-term memory (LTM) has limitless capacity
Transfer from STM to LTM
Factors that affect transfer of memory from STM to LTM include:
•Emotional state – we learn best when we are alert, motivated, and aroused
•Rehearsal – repeating or rehearsing material enhances memory
•Association – associating new information with old memories in LTM enhances
memory
Can you improve
your ability to
learn and
remember new
information?
YES!
Prove It Yourself…
Improve Your Memory
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The following techniques take
advantage of the brain’s storage and
retrieval
mechanisms:
Concentrate.
Paying attention
increases
brain activity—promoting consolidation of
information into long-term memory.
Minimize Interference.
Go where it is quiet. A noisy environment will impair your ability
to concentrate.
Break down large amount of information into smaller topic.
Give yourself time to
review each topic, and take a break in between.
Rephrase material in your own words.
Restate the information in a way that makes
sense to you personally.
Test yourself. Create outlines or diagrams. Use practice and review questions when they
are available.
Central Nervous System (CNS)
THE SPINAL CORD
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The spinal cord is a reflex
center and conduction
pathway which is found
within the vertebral canal.
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It extends from the
foramen magnum to L1 or L2.
Peripheral Nervous system (PNS)
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Nerve:
Nerve is a bundle of
neuron fibers found outside
the CNS.
▪ Cranial nerves:
▪ Cranial nerves are 12 pairs of nerves
that extend from the brain to serve
the head and neck region, except
the Vagus nerve, which extend into
the thorax and abdomen.
▪ Spinal nerves:
▪ Spinal nerves are 31 pairs of nerves
formed by the union of the dorsal
and ventral roots of the spinal cord
on each side.
Peripheral Nervous system (PNS)
The PNS has two (2) functional divisions…
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Sensory or Afferent Division:
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Consists of nerve fibers that convey
impulses to the central nervous system
from sensory receptors located in
various parts of the body.
▪ Sensory fibers that deliver impulses
from the skin, skeletal muscles, and
joints are called somatic (soma =
body) sensory fibers.
▪ Sensory fibers that transmit impulses
from the visceral organs are called
visceral sensory fibers, or visceral
afferents.
▪ The sensory division keeps the CNS
constantly informed of events going on
both inside and outside the body.
Motor or Efferent Division:
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Carries impulses from the CNS to
effector organs, muscles and glands.
Peripheral Nervous system (PNS)
Motor Division:
▪ The Somatic Nervous System
(SNS):
▪ Allows us to consciously, or
voluntarily, control our skeletal
muscles.
▪ This subdivision is often referred
to as the voluntary nervous
system, however, skeletal muscle
reflexes are also initiated
involuntarily by fibers of this same
subdivision.
▪ The Autonomic Nervous
System (ANS):
▪ Regulates events that are
automatic, or involuntary, such as
the activity of smooth muscles and
glands.
▪ This subdivision is commonly called
the involuntary nervous system
Peripheral Nervous system (PNS)
Motor Division (Autonomic Nervous
System):
◼ Sympathetic (stimulates)
It is the “fight or flight” subdivision,
which prepares the body to cope with
some threats
▪ Its activation results in increased
heart rate and blood pressure.
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Parasympathetic (inhibits)
It is the “housekeeping” system and is
in control most of the time.
▪ This division maintains homeostasis by
seeing that normal digestion and
elimination occur and that energy is
conserved.
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Nervous System
Reflex
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Reflexes are programmed,
rapid, predictable, and
involuntary responses to
stimuli.
Reflexes may be inborn or
learned (acquired)
Reflexes occur over neural
pathways called reflex arc
and involve both CNS and
PNS structures.
Reflex Arc
Five (5) Basic Element of Reflex Arc
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Receptor
Sensory neuron
Integration center
Motor neuron
Effector
Reflex
Types of Reflexes
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Somatic Reflexes – include all reflexes that stimulate the
skeletal muscle (e.g. When you quickly pulled your hand away
from a hot object, a somatic reflex is working).
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Autonomic Reflexes – regulate the activity of smooth muscles,
the heart, and glands (i.e. Secretion of saliva and changes in
the size of the eye pupils); autonomic reflexes regulate such
body functions as digestion, elimination, blood pressure and
sweating.
That’s
all…
Thank you for
listening.