Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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. 2

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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) 3

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 4

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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. 5

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 6

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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. 10

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins Cardiogenic Shock 11

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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] 12

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins SNS and PNS Effects on the Body 13

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins Neurotransmitters 14

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 post- synaptic neuron, or B) prevent the pre-synaptic neuron from the reuptake of natural neurotransmitters. 15

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 16

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 17

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 18

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 19

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 20

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins Practice Question: A resident of a long-term care facility receives a beta- adrenergic 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 21

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 22

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins 23