Adrenergics and the Nervous System

Adrenergics and the Nervous System

• Objectives:
  • Discuss the production and significance of cAMP and cGMP in smooth muscle cells.
  • Understand Alpha and Beta responses in respiratory care.
  • Differentiate adrenergic and cholinergic agents; incl. receptor types.

Nervous System Overview

• Central Nervous System (CNS):
  • Includes brain and spinal cord; control center.
• Peripheral Nervous System (PNS):
  • Composed of cranial and spinal nerves; connects CNS to the body.
  • Divisions:
  • Sensory (afferent): Impulse conduction from receptors to CNS.
  • Motor (efferent): Impulse conduction from CNS to effectors.
  • Autonomic Nervous System (ANS): Regulates involuntary actions (e.g., heart, glands).
  • Sympathetic Division: Activated during stress (fight-or-flight).
  • Parasympathetic Division: Conserves energy (rest-and-digest).

Receptors and Their Functions

• Adrenergic Receptors:

  • Accept Norepinephrine (NE).
  • Types:
  • Alpha (α): Vasoconstriction, ↑BP.
  • Beta one (β1): Increases heart rate and contractility.
  • Beta two (β2): Bronchodilation.

• Cholinergic Receptors:

  • Accept Acetylcholine (ACh).
  • Types:
  • Nicotinic (N): On post-synaptic neurons.
  • Muscarinic (M1, M2, M3): ↓HR and bronchoconstriction.

Bronchodilation Overview

• Types of Bronchodilators:
  • Sympathomimetics (Front Door): Mimic adrenaline for bronchodilation; e.g., β2 Agonists.
  • Anticholinergics (Back Door): Block ACh to relax airways.
  • Xanthines (Side Door): Relax airways by inhibiting phosphodiesterase.

Bronchoconstriction and Treatment

• Defined as the narrowing of airways due to:
  • Bronchospasm (involuntary muscle contraction).
  • Mucosal edema (inflammation).
  • Secretions.
• Treatments:
  • Use bronchodilators for bronchospasm.
  • Corticosteroids for mucosal edema.
  • Mucolytics for excessive secretions.

Sympathomimetics: Classifications

• Ultra-short acting: e.g., Epinephrine (<3 hrs).
• Short-acting (SABA): e.g., Albuterol (4-6 hrs).
• Long-acting (LABA): e.g., Salmeterol (12 hrs).

Adverse Effects of Bronchodilators

• Common effects: Tachycardia, tremors, palpitations, dizziness, nervousness, nausea.
• Important to monitor and address tolerance with repeated use of medications.