ans

Autonomic Nervous System (ANS) Overview

The Autonomic Nervous System (ANS) regulates involuntary body functions, divided into the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PNS).

Sympathetic Nervous System (SNS)

  • Stimulated by stress, exercise, and intense emotions; known as the "fight or flight" response.
  • Adrenergic response, using neurotransmitters: norepinephrine, epinephrine, and dopamine.
  • Receptor sites include Beta 1 (heart), Beta 2 (lungs), Alpha 1 (blood vessels), Alpha 2 (central nervous system), and Dopaminergic (kidneys).
  • Effects include increased blood pressure, cardiac output, heart rate, metabolic rate, muscle strength, respiration rate, pupil dilation, and bronchodilation.

Parasympathetic Nervous System (PNS)

  • Stimulated by rest and digestive activities; characterized as "Rest & Digest".
  • Cholinergic response using acetylcholine as a neurotransmitter.
  • Receptor sites: Muscarinic and Nicotinic.
  • Effects include relaxation of blood vessels in muscles, decreased heart rate, increased digestive enzyme secretion, constriction of bronchial smooth muscle, increased gland secretions, pupil constriction, and bladder contraction.

Adrenergic Agonists

  • Mimic SNS effects; examples include epinephrine, dopamine, albuterol, and pseudoephedrine.
  • Uses: anaphylaxis, cardiac arrest, asthma, hypotension, and glaucoma.
  • Adverse effects include tachycardia, hypertension, myocardial ischemia, and hyperglycemia.

Alpha 2 Agonists

  • Centrally acting; lower heart rate and blood pressure. Examples: clonidine and methyldopa.
  • Adverse effects: hypotension, drowsiness, dry mouth, fluid retention, and risk of rebound hypertension.

Adrenergic Antagonists

  • Include selective and nonselective alpha and beta blockers.
  • Alpha 1 blockers (e.g., doxazosin) relieve outflow obstruction in conditions like BPH; adverse effects include orthostatic hypotension and sexual dysfunction.
  • Beta blockers (e.g., propranolol, metoprolol) decrease heart rate and myocardial workload, used for heart failure and anxiety, with adverse effects including bradycardia and bronchospasm.
  • Contraindicated in symptomatic bradycardia and significant lung disorders, and patient education is essential regarding pulse monitoring and gradual withdrawal.