The nervous system with questions

The Nervous System
 Is Responsible For:
 Allowing us to interact w/ environment
 Regulation of activities involving internal organs
 „Driving‟ the other sys. of the body
 Network composed of complex structures, that transmit
signals:
 Electrically
 Chemically
… b/w the body‟s organs, tissues & brain

Organization of the Nervous System

 Central Nervous System:
 comprised of the Brain
& Spinal Cord

 Peripheral Nervous System (PNS) pathways are
differentiated:
 Afferent pathways (sensory): ascending.
 sensory impulses toward CNS
 Efferent pathways (motor): descending.
 motor impulses away from CNS
 Somatic NS: voluntary control (i.e. skeletal muscle
contraction)
 Autonomic NS: involuntary control (i.e. subconscious
reg. of body‟s internal environment: resp., HR,
digestion)

 Autonomic NS:
 Sympathetic NS:
 Nerves originating from thoracic & lumbar regions
of spinal column
 Parasympathetic NS:
 Nerves originating from the brain & sacrum

2 Basic Cells w/in the N. System
 Neuron
 Primary cell of N.Sys.
 Fxnal unit of N.Sys.
 Different types
 (Neuroglial Cells)
 Supporting cells:
 Structural support
 Nutrition
 Schwann Cells
 Astrocytes
 Microglial Cells

 100 Billion neurons present in our NS
 ~7 miles of axons (connections)
 One neuron connects with 10,000 other neurons (on
average)
 Some of the more important connections are up to 6ft
long
 Therefore increased metabolic demands!
 Many diseases that affect energy affect the Nervous
System.
 Organ of consciousness, emotions, behavior, intellect &
humanity.

The Neuron
 Can work alone, or in units
 Detect environmental changes & initiate body responses
to maintain a dynamic steady state (Homeostasis)
 Structures differ, so that each neuron is adaptable to
perform specialized fxns. {differentiated}
 Cannot regenerate entirely
 Cell division stops at birth: (G1)

3 Parts to a Neuron:
1. Cell Body: Soma
2. Dendrites: thin processes / extensions:
• carries impulses toward cell body

The Three Parts to a Neuron
3. Axon: projection away from cell body.
• Carries impulses away from it.
• Covered with myelin (lipid insulating layer - called
‘myelin sheath’).
• Increases the velocity of impulse transmission
• Diameter of axon also influences impulse
transmission velocity.
 De-myelinating Diseases:
 MS & Guillain-Barre Syndrome

Integrating the INPUT with the OUTPUT
 The NS has only 3 main (overlapping) jobs:
 Sensory Input: Informing
the CNS:
 Organizing what is happening inside
& outside the body
 Allows info from body receptors (i.e.
Skin) to create an impulse
 that shoots up to the Spinal Cord
& then to the brain

 Integration: CNS makes ‘sense’
of received input from around
the body.
 i.e. Interneurons: neuron
(nerve cell) sits b/w a sensory
fiber & a motor fiber.
 Interneurons bring an
impulse / stimulus to the
CNS, and back to the
nerves that can make an
action happen

 Motor Output:
 The stimulation of
muscles to move
 The stimulation of
glands to secrete
substances
 i.e. Motor fibers- are
„action making‟
nerves

Transmission of the Nerve Impulse
 Impulses have a domino-like effect
 When a neuron get a signal, it passes it onto the next
neuron; which passes it onto the next neuron; which
passes it onto the next neuron; etc.
 def. Nerve-a long collection of neurons
 Entire impulse passes through a neuron in about 7
milliseconds
 How? The Action Potential

The Action Potential
 When neuron at rest: „resting membrane potential‟
 Cell membrane is Polarized
 More Na+ outside; More K+ inside
 When a stimulus reaches resting neuron:
 Gated Na+ channels open on the surface of membrane
 Na+ rushes into the cell
 Inside of the cell becomes (+)
 This Depolarizes the cell
 Creates an ACTION POTENTIAL
 Transmits the stimulus
 ALL–or–NONE: need to overcome threshold

 Movement of K+ Outside the Cell:
 K+ gates open, cause K+ to escape outside
 Na+ gates close
 Closing of K+ gates:
 More K+ outside the cell than Na+ inside the cell
 The cell is now in a HYPERPOLARIZED STATE

 Refractory Period: puts everything back to normal
 K+ returns inside & Na+ returns outside
 Because of the Na+/K+ Pump!
 During refractory period, the neuron DOES NOT
respond to ANY incoming stimuli

Transmission of the Nerve Impulse:
The Synaptic Cleft
 This is the gap that separates the axon of one neuron &
the dendrites of another.
 Neurons NEVER touch each other!
 How does the signal get transmitted?
 The depolarization wave reaches the end of the axon
& causes Ca2+ ion channels to open, on the
presynaptic neuron
 Ca2+ enters the presynaptic axonal terminal & fuses
with the NT vesicles (synaptic vesicles)
 NT then gets released into the synapse

The Synaptic Cleft
 NT binds with protein receptors on the dendrites of the
postsynaptic neuron. (NTs have specific receptors)
 2 things can now occur. The NT can:
 stimulate Na+ channels to open. This continues the
impulse [EPSP]
 stimulate K+ channels to open. This hyper-polarizes
the cell & stops the impulse [IPSP]
 The NT then goes back to the presynaptic neuron & gets
recycled for the next impulse transmission

Sympathetic Response
 Cardiovascular Increases in:
 B/P ; HR ; Contractility ; B.flow to Skeletal Muscles.
 Respiratory Efficiency Increases:
 Bronchial dilation ; RR increases
 Pupil Dilation & Sweating Increase
 Piloerection
 Shunting of blood way from GI Tract.
 Shunting of blood away from kidneys.
 Glyconeogenesis & Glycogenolysis.
 Release of Corticosteroids.
 Suppression of Immune & Inflammatory responses.

Sympathetic Transmission Termination
 Once NEpi has been released in the synaptic cleft it
must be removed.
 Effective recycling of NEpi.
 Enzymatic metabolization by:
 Monoamine oxidase (MAO)
 Catechol-o-methyltransferase (COMT)

Click on right answer to go to next page
The nurse monitors for which clinical manifestations
in the client receiving a medication that stimulates
the sympathetic division of the autonomic nervous
system?
a. Decreased heart rate, decreased force of
contraction
b. Increased heart rate, increased force of
contraction
c. Decreased heart rate, increased force of
contraction
d. Increased heart rate, decreased force of
contraction

Correct Answer is B
Stimulation of the sympathetic nervous system
initiates the fight-or-flight response, increasing
both the heart rate and force of contraction.

Parasympathetic Response
 Increase motility and secretions in the GI tract to
promote digestion and absorption.
 Relaxation of GI/GU sphincters - evacuation of wastes.
 Decrease HR, B/P & contractility- to conserve energy &
provide rest to the heart
 Bronchial Constriction & Increased secretions from
bronchial mucosa.
 Pupillary constriction, thereby decreasing light entering
eye (decreases stimulation of the retina).

Parasympathetic Transmission
Termination
 Once ACh has been released in the synaptic cleft it must
be removed.
 Effective recycling of Ach.
 Enzymatic metabolization by:
 Acetylcholinesterase

Click on correct answer to move to next slide:
In preparation for magnetic resonance
angiography, the nurse asks the client which question?
a. “Have you had a recent blood transfusion?”
b. “Do you have allergies to iodine or shellfish?”
c. “Do you have a history of urinary tract
infections?”
d. “Do you currently use oral contraceptives?”

Correct Answer :B
Allergies to iodine and/or shellfish need to be explored
because the client may have a similar reaction to the
dye used in the procedure. In some cases, the client
may need to be premedicated with antihistamines or
steroids before the test.

Neurotransmitters >30 NTs:
 NEpi & Epi
 ACh
 Dopamine
 Histamine
 Serotonin
 AAs (i.e. GABA)
 Enkephalins
 Endorphins

Thinking about your Brain
 The brain weighs only 3
pounds & requires 15-20%
of the total CO
 Different parts of your
brain are responsible for
different fxns
 Major parts of brain:
 Cerebrum
 Cerebellum
 Brain Stem
 Diencephalon
 4 connective cavities of
the brain (ventricles)

Cerebrum Largest part of brain
 Controls consciousness
 Divided in L / R halves
called Cerebral
Hemispheres
 Each 1/2 has 4 lobes:
 Frontal
 Parietal
 Temporal
 Occipital

 Cortex (cerebrum’s outer layer)- is gray
 The „curvy bumps‟ are called gyri
 Shallow grooves that separate the gyri are called
sulci.
 Deeper grooves are called fissures
 The Corpus Callosum is located at the base of the
longitudinal fissure
 network of myelinated fibers that join the L & R
cerebral hemispheres

Frontal Parietal Temporal Occipital
Speech
Production
General
Interpretation
Area
Interpretation
of
Sensations
Recognizing
objects
visually
Concentration Understanding
speech
Remembering
visually
Vision
Problem
solving
Ability to use
words
Remembering
through
sounds
Combining
images received
visually
Planning
Exec. Fxns
Sensations
felt
Hearing
Voluntary
muscle
control
Learning

Which deficit will the nurse expect to find in
a client who has experienced an injury to
the frontal lobe of the brain?
Choose the right answer to move to the next slide:
 a. Inability to interpret taste sensations
 b. Inability to interpret sound
 c. Impaired judgment
 d. Impaired learning

 Yes, the answer is “C”: Impaired judgment
 The frontal lobe is responsible for many
functions, including judgment, reasoning,
voluntary eye movement, and motor
functions.

Cerebellum Lies just below the cerebrum
 Divided by a fissure
 Gray on the outside
 Controls & coordinates
skeletal muscle mvmts. [The
cerebrum sends out the
signal to the cerebellum for
mvmt]
 Maintains muscle tone (at all
times)

The Brain Stem
 Comprised of 3 structures:
 Midbrain: “station” for info. passing b/w:
 SC & cerebrum
 SC & cerebellum
 Pons: “bridge” that joins the cerebellum with the
cerebrum
 Filled w/ axonal bundles that
integrate info. from eyes & ears
 Controls respirations
 Medulla Oblongata:
 HR; Resps; B/P regulation
 Centers for
coughing, vomiting, sneezing, swallowin
g & hiccups
 Becomes the SC after it passes through the
foramen magnum

The Reticular Formation
 Collection of nerve cell bodies (nuclei)
within the brainstem called the
Reticular Formation
 Controls vital reflexes:
 Cardiovascular fxning
 Respiration
 Maintains wakefulness

Bypassing the Brain-The Reflex Arc
 Happen automatically (i.e. When you touch something
very hot or sharp)
 Sensory neurons detect: Pain / Temp / Pressure
 If a sensory neuron detects something that could harm
your body (i.e. Sharp object)
 An impulse passes from the receptor throughout
the sensory neuron, to the SC & then to a motor
neuron, which stimulates muscles to retract your
finger from the sharp object.

Bypassing the Brain - The Reflex Arc
 Reflexes occur so fast - you don‟t even think
(cognitively) about how to react!
 The impulse does not make it to the brain in time to
generate a rxn!
By the time the impulse gets to the brain, the SC has
already taken care of the problem.
 Reflex Arcs:
 Save time & damaging consequences

The Ventricles
 2 Lateral: one on each side of the brain
 3rd: in the center of the brain
 4th: lies on the top of the brainstem
 Cerebral Aqueduct connects the 3rd & 4th ventricles
together & becomes the central canal of the SC

 The ventricles & cerebral aqueduct serve as a system to
circulate CSF
 CSF is a clear fluid that is made by the cells that line the
ventricles
 CSF is contained in the 4 ventricle, the subarachnoid
space & the central canal of the SC. Fxns to:
 Pick up wastes
 Cushions the CNS
 Keeps the ions in balance
 Stabilizes the membrane potentials.

Spinal Tap CSF is drawn through a
needle for analysis from
the subarachnoid space
 Can be tested for:
 presence of bacteria
(which may cause
meningitis)
 presence of proteins
that can indicate
other diseases (i.e.
Alzheimer's)

Regulating Systems : The Diencephalon
 Made up of the Hypothalamus & Thalamus
 Hypothalamus regulates:
 Sleep
 Hunger & Thirst
 Body Temp
 B/P
 Fluid Levels
 Maintains Homeostasis
 Controls pituitary gland signaling to the
Endocrine System, for secreting hormones

Regulating Systems : The Diencephalon
 Thalamus is the gateway to the cerebrum.
 Whenever an impulse travels from somewhere in
your body, it passes through the Thalamus
 The Thalamus then relays the impulse to the proper
location in the cerebral cortex, which then interprets
the message

Click on right answer to move to next slide:
During electroencephalography, the client is instructed to
breathe deeply (hyperventilate). What is the nurse’s
interpretation of this action?
a. Seizure activity may be increased because of
cerebral vasodilation associated with hyperventilation.
b. Seizure activity may be increased because of
cerebral vasoconstriction secondary to hyperventilation.
c. Seizure threshold is lowered by acidosis associated
with hyperventilation.
d. Seizure threshold is lowered by hypoxemia
associated with hyperventilation.

Correct Answer B
Hyperventilation produces cerebral
vasoconstriction and alkalosis, which
increases the likelihood of seizure activity.
The client is asked to breathe deeply 20 to
30 times for 3 minutes.

Disorders of the NS
 Multiple Sclerosis (MS)
 Affects the myelin sheath that covers the axon of a
nerve
 The myelin sheath develops lesions that become
inflamed & irritated.
 Leads to demyelination of the white matter of the
brain & spinal cord
 After the myelin destruction, neuroglial tissue
proliferates in the white matter of the CNS. When the
lesion heals, hard yellow scar tissue (plaques) are left
behind.

 As the disease affects more nerves, the number of
scleroses increases, leading to multiple damage sites
 The hard scar tissue interferes w/ the nerve‟s ability to
conduct an impulse through the axon
 If an impulse can‟t be transmitted, a mvmt or
response cannot occur
 As the dx progresses, mvmt becomes increasingly
difficult & then impossible

Structures most commonly involved are the optic &
occulomotor nerves & the spinal tract nerves. Does not
affect the Peripheral NS
 Characterized by exacerbations & remissions
 Seen primarily in ages 18 – 40 y/o. [ F > M ]
 Exact cause is unknown:
 Slow acting viral infection?
 An autoimmune response? GENETICS?
 An allergic response?
 Trauma; anoxia; toxins; nutritional deficiencies;
vascular lesions; anorexia?

Alzheimer‟s Disease
 „mind‟ slipping away
 Progressive degenerative disorder of the cerebral cortex
{Cortical Degeneration}
 Accounts for >1/2 of all cases of Dementia
 Pt‟s can‟t care for themselves. They‟ve forgotten how to
perform ADLs.
 Bundles of a fibrous protein [ADAP: Alzheimer‟s Dx
Assoc. Protein] , are tangled around the nucleus of a
neuron
 Amyloid plaques (globs of protein) also surround
axonal branches. Plaques are thought to kill / destroy
the neuron

 Cause unknown:
 Neurochemical factors:
 Possible deficiencies:
 *ACh; Somatostatin; Substance-P; NEpi
 Slow-growing CNS virus?; Trauma ?
 Genetics (abnormal chromosome 21)
 Insidious Onset & Cannot be completely confirmed till
after death
 Tests that can help diagnose possibility:
 PET (Positron Emission Tomography)
 CT ; MRI; EEG
 CSF analysis; Cerebral Angiogrophy

http://web.kamogawa.ne.jp/~miyake/ADunrabelingADEAR/ADEAR2003.htm

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