II. Effects: Alpha Receptor General

  1. Vascular Smooth Muscle
    1. Skin and skeletal Muscle vessel constriction
    2. Splanchnic vessel constriction
  2. Gastrointestinal
    1. Myenteric Plexus Inhibition
  3. Genitourinary
    1. Pregnant Uterus contraction
    2. Penis and seminal Vesicle ejaculation
  4. Skin
    1. Pilomotor smooth Muscle Contraction
    2. Apocrine gland contraction
  5. Metabolic
    1. Gluconeogenesis
    2. Glycogenolysis

III. Effects: Alpha 1 Receptors

  1. Vascular Smooth Muscle postsynaptic Neurons
    1. Vasoconstriction
  2. Myocardium
    1. Positive Inotrope (increase cardiac contractility)
    2. Negative Chronotrope (decrease Heart Rate)
  3. Eye
    1. Radial Muscle Contraction (dilate pupils)
  4. Gastrointestinal and Genitourinary
    1. Sphincter (e.g. anus) contraction

IV. Effects: Alpha 2 Receptors

  1. Peripheral Alpha 2 Receptors
    1. Vascular Smooth Muscle (mixed effect)
      1. Modulates large vessel tone
      2. Arteriolar and venous Vasoconstriction
      3. Opposes alpha 1 receptor Vasoconstriction
        1. Inhibits Norepinephrine release
        2. Decreases adrenergic activity
    2. Gastrointestinal
      1. Smooth Muscle wall relaxation
    3. Metabolic
      1. Fat Cell Lipolysis
  2. Central Alpha 2 Receptors (CNS)
    1. Inhibits Locus Ceruleus reflex arc
    2. Peripheral vasodilatation

V. Medications: Alpha Adrenergics

  1. Alpha Adrenergic Agonist (Alpha Adrenergic Receptor)
    1. Alpha Non-Specific
      1. Epinephrine
      2. Norepinephrine
    2. Alpha 1 Selective
      1. Phenylephrine
      2. Methoxamine
    3. Alpha 2 Selective
      1. Clonidine (See Central Adrenergic Agonist)
      2. Alpha-methylnorepinephrine
  2. Alpha Receptor Antagonist
    1. Alpha Non-Specific
      1. Phentolamine
    2. Alpha 1 Selective
      1. Prazosin (See Alpha Adrenergic Antagonist)
      2. Phenoxybenzamine
    3. Alpha 2 Selective
      1. Yohimbine
      2. Tolazoline

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