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Understanding the Autonomic Nervous System

Apr 1, 2025, 1 hour 51 minutes

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Lecture Notes: Autonomic Nervous System and Prioritization

Additions to Unit Material

  • Unit 5 Material: New sheet with blood pressure medicines added.
  • Test Preparation: Includes scenarios related to prioritization.
  • Prioritization Strategy: Start with ABCs (Airway, Breathing, Circulation), then Maslow’s hierarchy (physiological over social), acute vs. chronic problems.

Autonomic Nervous System (ANS)

  • Main Components:
    • Sympathetic Nervous System (SNS): 'Fight or Flight'. Prepares body for stressful situations.
    • Parasympathetic Nervous System (PNS): 'Rest and Digest'. Focuses on conserving energy.
  • ANS Features:
    • Involuntary control, psychological/social triggers.
    • Functions to maintain homeostasis.

Sympathetic Nervous System (SNS)

  • Functions:
    • Activated during stress; prepares body to flee or fight (e.g., adrenaline release).
    • Increases heart rate, dilates pupils, inhibits GI functions.
    • Related to increased energy, blood glucose release from the liver.

Parasympathetic Nervous System (PNS)

  • Functions:
    • Activated during rest; focuses on digestion and recovery.
    • Reduces heart rate, constricts pupils, stimulates GI functions.

Key Neurotransmitters and Receptors

  • **Sympathetic:
    • Neurotransmitters:** Epinephrine (adrenaline), Norepinephrine.
    • Receptors: Alpha (α) and Beta (β) receptors.
  • **Parasympathetic:
    • Neurotransmitter:** Acetylcholine.
    • Receptors: Muscarinic receptors.
  • Receptor Functions:
    • Alpha-1: Vasoconstriction, increases blood pressure.
    • Beta-1: Increases heart rate.
    • Beta-2: Bronchodilation (lungs).
    • Muscarinic: Various effects including decreased heart rate and increased secretions.

Medications and Effects

  • Beta Agonists (e.g., Albuterol): Activate β2 receptors for bronchodilation.
  • Beta Blockers (e.g., Propranolol): Non-specific; can affect both heart and lungs, potential asthma trigger.
  • Alpha Blockers (e.g., Prazosin): Cause arterial dilation, lower blood pressure.
  • Acetylcholinesterase Inhibitors: Increase acetylcholine levels; used in treating myasthenia gravis.

Clinical Scenarios and Considerations

  • Cholinergic Crisis: Excess acetylcholine (e.g., from pesticides) leading to parasympathetic overload (e.g., diarrhea, salivation).
  • Anticholinergic Crisis: Drug overdose leading to symptoms like dry mouth, tachycardia.
  • Emergency Treatments: Use of atropine to counteract cholinergic effects, epinephrine in anaphylaxis.

Mnemonics for Toxicity

  • DUMBELLS (Cholinergic): Diarrhea, Urination, Miosis, Bradycardia, Emesis, Lacrimation, Salivation.
  • MAD AS A HATTER (Anticholinergic): Hot, Red, Dry, Blind, Mad.

Exam Preparation Tips

  • Understand receptor locations and effects of their activation/blockage.
  • Familiarize with terms like agonists, antagonists, mimetic, lytic.
  • Review highlighted medications in the pharmacology textbook.

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