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Understanding Adrenergic Agents in Nervous System Functions

Gain knowledge on adrenergic drugs, neurotransmitters, nervous system divisions, and receptor types, including alpha and beta responses. Explore how adrenergic agents affect body systems and their effects on muscle activity and pain relief.

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Understanding Adrenergic Agents in Nervous System Functions

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  1. Adrenergic agemts

  2. Learning Objectives • Understand the central and peripheral nervous systems, their functions, and their relationship to drugs. • Become aware of the role of neurotransmitters. • Learn how adrenergic drugs affect body systems and where they work in the body.

  3. Learning Objectives • Define the action of neuromuscular blocking agents in reducing muscle activity. • Distinguish between narcotic and nonnarcoticanalgesia. • Become familiar with the various types of agents for migraine headaches.

  4. Divisions of the Nervous System • Central Nervous System • Brain • Spinal cord • Peripheral Nervous System • Nerves • Sense organs

  5. Divisions of the Nervous System • Central Nervous System • Peripheral Nervous System

  6. Divisions of the Nervous System • Central Nervous System • Peripheral Nervous System • Somatic Nervous System • Autonomic Nervous System

  7. Divisions of the Nervous System • Central Nervous System • Peripheral Nervous System • Somatic Nervous System Voluntary action: skeletal muscle contraction and movement • Autonomic Nervous System Involuntary activities: respiration, circulation, digestion, sweating

  8. Autonomic Nervous System

  9. Review The nervous system has two components. What are they?

  10. Review The nervous system has two components. What are they? Answer • Central nervous system (CNS) • Peripheral nervous system (PNS)

  11. Major Neurotransmitters • Acetylcholine • GABA • Dopamine • Epinephrine • Serotonin

  12. Major Neurotransmitters • Acetylcholine (ACh) • Smooth muscle, cardiac muscle, and exocrine glands • Anticholinergics block ACh receptors • GABA • Dopamine • Epinephrine • Serotonin

  13. Major Neurotransmitters • Acetylcholine • GABA (gamma-aminobutyric acid) Regulates message delivery system of the brain • Dopamine • Epinephrine • Serotonin

  14. Major Neurotransmitters • Acetylcholine • GABA • Dopamine Acts on the CNS and kidneys • Epinephrine • Serotonin

  15. Major Neurotransmitters • Acetylcholine • GABA • Dopamine • Epinephrine • Acts on cardiac and bronchodilator receptors • Known as Adrenaline • Serotonin

  16. Major Neurotransmitters • Acetylcholine • GABA • Dopamine • Epinephrine • Serotonin • Acts on smooth muscle and gastric mucosa (causes vasoconstriction) • Emotional responses: depression, anxiety

  17. Communication by Neurotransmitters Neurotransmitters are released from one axon and received by another neuron’s dendrites.

  18. Discussion What are three important types of receptors in the study of drugs?

  19. Discussion What are three important types of adrenergic receptors in the study of drugs? Answer • Alpha • Beta-1 • Beta-2

  20. Types of Receptors • Alpha Vasoconstriction, raise BP • Beta-1 Heart stimulation • Beta-2 Vasodilation and bronchodilation

  21. Drugs Affecting TheAutonomic Nervous System Adrenergic Agents and Adrenergic-Blocking Agents

  22. The Sympathetic Nervous System in Relationship to the Entire Nervous System

  23. Adrenergic Agents • Drugs that stimulate the sympathetic nervous system (SNS)

  24. Adrenergic Agents Also known as • adrenergic agonists or sympathomimetics

  25. Adrenergic Agents Mimic the effects of the SNS neurotransmitters: • norepinephrine (NE) and epinephrine (EPI)

  26. Adrenergic Receptors • Located throughout the body • Are receptors for the sympathetic neurotransmitters Alpha-adrenergic receptors: respond to NE Beta-adrenergic receptors: respond to EPI

  27. Alpha-Adrenergic Receptors • Divided into alpha1 and alpha2 receptors • Differentiated by their location on nerves

  28. Alpha1-Adrenergic Receptors • Located on postsynaptic effector cells (the cell, muscle, or organ that the nerve stimulates)

  29. Alpha2-Adrenergic Receptors • Located on presynaptic nerve terminals (the nerve that stimulates the effector cells) • Control the release of neurotransmitters

  30. The predominant alpha-adrenergic agonist responses are: • Vasoconstriction and CNS stimulation

  31. Beta-Adrenergic Receptors All are located on postsynaptic effector cells • Beta1-adrenergic receptors—located primarily in the heart • Beta2-adrenergic receptors—located in smooth muscle of the bronchioles, arterioles, and visceral organs

  32. The beta-adrenergic agonist response results in: • Bronchial, GI, and uterine smooth muscle relaxation • Glycogenolysis • Cardiac stimulation

  33. Dopaminergic Receptors • An additional adrenergic receptor • Stimulated by dopamine • Causes dilation of the following blood vessels, resulting in INCREASED blood flow • Renal • Mesenteric • Coronary • Cerebral

  34. Adrenergic Receptor Responsesto Stimulation LOCATION RECEPTOR RESPONSECardiovascular Blood vessels alpha1 and beta2 Constriction / dilation Cardiac muscle beta1 Increased contractility AV Node beta1 Increased heart rate SA Node beta1 Increased heart rate

  35. Adrenergic Receptor Responsesto Stimulation LOCATION RECEPTOR RESPONSEGastrointestinal Muscle beta2 Decreased motility Sphincters alpha1 Constriction

  36. Adrenergic Receptor Responsesto Stimulation LOCATION RECEPTOR RESPONSEGenitourinary Bladder alpha1 Constrictionsphincter Penis alpha1 Ejaculation Uterus alpha1 and beta2 Contraction/ relaxation

  37. Adrenergic Receptor Responsesto Stimulation LOCATION RECEPTOR RESPONSERespiratory Bronchial beta2 Dilation/relaxationmuscles

  38. Catecholamines Substances that can produce a sympathomimetic response Endogenous: • epinephrine, norepinephrine,dopamine Synthetic: • isoproterenol, dobutamine, phenylephrine

  39. Adrenergic Agents Mechanism of Action Direct-acting sympathomimetic: • Binds directly to the receptor and causes a physiologic response

  40. Direct-Acting Sympathomimetics

  41. Adrenergic Agents Mechanism of Action Indirect-acting sympathomimetic: • Causes the release of catecholamine from the storage sites (vesicles) in the nerve endings • The catecholamine then binds to the receptors and causes a physiologic response

  42. Indirect-Acting Sympathomimetics

  43. Adrenergic Agents Mechanism of Action Mixed-acting sympathomimetic: • Directly stimulates the receptor by binding to it AND • Indirectly stimulates the receptor by causing the release of stored neurotransmitters from the vesicles in the nerve endings

  44. Mixed-Acting Sympathomimetics

  45. Drug Effects of Adrenergic Agents Stimulation of alpha-adrenergic receptors on smooth muscles results in: • Vasoconstriction of blood vessels • Relaxation of GI smooth muscles • Contraction of the uterus and bladder • Male ejaculation • Decreased insulin release • Contraction of the ciliary muscles of the eye (dilated pupils)

  46. Drug Effects of Adrenergic Agents Stimulation of beta2-adrenergic receptors on the airways results in: • Bronchodilation (relaxation of the bronchi) • Uterine relaxation • Glycogenolysis in the liver

  47. Drug Effects of Adrenergic Agents Stimulation of beta1-adrenergic receptors on the myocardium, AV node, and SA node results in CARDIAC STIMULATION: • Increased force of contraction (positive inotropic effect) • Increased heart rate (positive chronotropic effect) • Increased conduction through the AV node (positive dromotropic effect)

  48. Adrenergic Agents: Therapeutic Uses • Anorexiants: adjuncts to diet in the short-term management of obesity Examples: benzphetamine phentermine dextroamphetamine Dexedrine

  49. Adrenergic Agents: Therapeutic Uses Bronchodilators: treatment of asthma and bronchitis • Agents that stimulate beta2-adrenergic receptors of bronchial smooth muscles causing relaxation Examples: albuterol ephedrine epinephrineisoetharine isoproterenol levalbuterolmetaproterenol salmeterol terbutaline • These agents may also affect uterine and vascular smooth muscles.

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