Download Fundamentals of the Nervous System

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Fundamentals
of the Nervous
System
1
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Summary
The nervous system is divided into
two main branches and two divisions:
Branches
• The Central Nervous system
• The Peripheral nervous system
Divisions
• The efferent division has neurons that carry signals
away from the brain and spinal cord to the periphery
(the body)
• The afferent division contains neurons that carry
impulses from the periphery to the CNS.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
2
Function of the Autonomic
Nervous System
• The ANS is an involuntary
system responsible for
the control of smooth
muscle.
• The connection
between neurons and
organs or tissues relies
on neurotransmitters
and synaptic
transmission.
• The autonomic nervous
system (ANS) is
subdivided into:
• Sympathetic nervous
system (SNS)
• Parasympathetic
nervous system (PNS)
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Autonomic Nervous System:
Sympathetic
• Central Nervous System (CNS) excitatory
sympathetic neuron activation
• Responds to stress or danger
• Initiate the fight-or-flight response
• Chief neurotransmitters are called ADRENERGIC
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Alarm or Acute Stress
• Adrenal glands release epinephrine to …
• Enhance strength and speed
• Dilate pupils for better vision
• Shunt blood away to the muscles, heart, lungs
• Corticosteroids release from the adrenal glands to …
• Increase muscle endurance and stamina
• Decrease nonessential functions like digestion
• Inhibit reproduction, growth and immunity
• Endorphins are released to…
• Reduce sensitivity to pain and injury.
• Interact with opioid receptors in the brain to limit the
perception of pain.
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5
DIRECT SNS ADRENERGIC DRUGS
• The therapeutic uses of sympathetic drugs are related to
providing extra-adrenergic stimulation.
• One of the most frequent indications for adrenergic
agonist drugs is shock:
• Tachycardia
• Severe hypotension
• Circulatory collapse
• Shock is the result of inadequate tissue perfusion,
leaving the cells without the oxygen and nutrients they
need to function normally and survive.
Prototype drug: Epinephrine
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6
Epinephrine:
Core Drug Knowledge
• Pharmacotherapeutics
• Wide variety of indications—asthma, shock, etc.
• Pharmacokinetics
• Administered—parenterally, topically, or by
inhalation. Metabolism: liver. Absorption: into the
tissues. Excreted: kidneys. Duration: 1 to 4 hours.
• Pharmacodynamics
• It stimulates all adrenergic receptors and causes
adverse effects in the cardiovascular system and
CNS.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Epinephrine
• Contraindications and precautions
• Absolute contraindications to epinephrine
include hypersensitivity, sulfite sensitivity,
closed-angle glaucoma, and using during labor.
• Adverse effects
• Severe adverse effects include hypertensive
crisis, angina, cerebral hemorrhage, and cardiac
arrhythmias.
• Drug interactions
• Tricyclic antidepressants, oxytocin, some
anesthetics, and beta-adrenergic drugs.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Epinephrine
• Maximizing therapeutic effects
• Close monitoring of vital signs
• Careful monitoring for adverse effects.
• Minimizing adverse effects
• When treating anaphylactic shock, monitor
blood pressure.
• Assisting the patient with menu planning may
help to promote appetite and counteract the
anorectic influence of epinephrine.
• Monitor and treat insomnia
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Adrenergic Receptor Agonist
• Adrenergic receptors located throughout the body are
important in blood pressure control:
• Alpha-adrenergic (Alpha-1 and Alpha-2) receptors
• Beta-adrenergic receptors - antagonists
[We will discuss these in more depth later in the semester]
Beta-adrenergic Agonist
• Dopamine creates norepinephrine with use of other
chemicals like beta-hydroxylase. Norepinephrine is a then
precursor neurotransmitter to epinephrine.
Dopamine is important in emergency cardiac
treatment to support circulation, prevent circulatory
collapse and raise blood pressure.
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10
Cardiogenic Shock
https://www.youtube.com/watch?v=GTZ8Zh8jPxA
11
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Autonomic Nervous System:
Parasympathetic
• The Autonomic Nervous System (ANS) maintains
regulatory functions of the body e.g. bowels,
bladder, digestion, blood flow, heart rate
• Chief neurotransmitters are called CHOLINERGIC
• Drugs can have cholinergic effects or side effects
[Will be covered in later lectures]
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12
SNS and PNS Effects on the Body
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Neurotransmitters
https://www.youtube.com/watch?v=p5zFgT4aofA
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REVIEW: Agonists and Antagonists
Agonists are medications that mimic natural
neurotransmitters thus “turning on” their receptors.
Antagonists are medications that either:
A) block natural chemicals at the postsynaptic neuron, or
B) prevent the pre-synaptic neuron from the
reuptake of natural
neurotransmitters.
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Practice Question:
A priority nursing assessment for a patient who is to
receive an alpha- or beta-adrenergic antagonist would be
to:
A. Assess heart rate
B. Check blood glucose
C. Measure urinary output
D. Monitor respiratory rate
Answer: A. Assess heart rate
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Practice Question:
A nurse in the intensive care unit is caring for a patient in
shock and has started IV administration of dopamine. For
a patient in shock, dopamine helps to:
A. Decrease heart rate
B. Decrease blood pressure
C. Increase blood pressure
D. Increase body temperature
Answer: C. Increase blood pressure
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Practice Question:
A patient is prescribed regular doses of epinephrine.
Which of the following nursing diagnoses is related to
comfort and is most appropriate for this patient?
A. Imbalanced Nutrition: Less than body
requirements
B. Disturbed Sleep Pattern: Insomnia due to CNS
excitation
C. Disturbed Sensory Perception
D. Ineffective Tissue Perfusion
Answer: B. Disturbed Sleep Pattern
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18
Practice Question:
A patient has recently been prescribed a drug that
treats his hypertension by blocking the sympathetic
receptors in his sympathetic nervous system. This
action is characteristic of:
A. An adrenergic antagonist
B. An adrenergic agonist
C. A cardiotonic
D. A neurotransmitter
Answer: A. An adrenergic antagonist
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19
Practice Question:
A 21-year-old man experienced massive trauma and
blood loss during a motorcycle accident and has been
started on a dopamine infusion upon his arrival at the
hospital. In light of this drug treatment, what
assessment should the care team prioritize?
A. Respiratory assessment
B. Arterial blood gases
C. Cardiac monitoring
D. Monitoring of intracranial pressure
Answer: C. Cardiac monitoring
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20
Practice Question:
A resident of a long-term care facility receives a betaadrenergic antagonist (beta-blocker) called metoprolol
(Lopressor) at 8 AM and 8 PM daily. Before
administering this drug, the nurse should perform and
document what assessments?
A. Oxygen saturation and respiratory rate
B. Heart rate and blood pressure
C. Level of consciousness and pain rating
D. Temperature and respiratory rate
Answer: B. Heart rate and blood pressure
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21
Practice Question:
Which of the following patients is most likely to benefit
from the administration of an adrenergic agonist?
A. A man who is in cardiogenic shock following a
myocardial infarction (“heart attack”)
B. A man who has a diagnosis of primary hypertension
C. A woman who has been admitted with suspected
ischemic stroke
D. A woman who is in labor and may need a cesarean
section
Answer: A. A man who is in cardiogenic shock
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