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PDA Block 2 > Smooth Muscle > Flashcards

Smooth Muscle Flashcards

1
Q

Mechanisms of Smooth Muscle Contraction:

A
  • **Electromechanical Coupling: **operates through changes in cell membrane potential
    • Resting membrane potential = -40 to -70 mV
  • **Pharmacomechanical Coupling: **operates independent of cell membrane potential
    • Receptors / Intracellular Signaling
  • Neurotransmitters, Hormones, Paracrine Factors
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2
Q

What are the 3 pathways involved in smooth muscle contraction:

A
  1. Eletrochemical signaling
  2. Rho kinase pathway
  3. Mysoin light chain kinase
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3
Q

Mechanisms of Smooth Muscle Relaxation:

A
  • Inhibit contractile mechanisms
  • Paracrine factors – nitric oxide, dopamine, prostacyclin
  • Membrane potential
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4
Q

What are some therapeutic applications for smooth muscle relaxation?

A
  • Cardiovascular – vasodilators
  • Obstetrics – uterine relaxation
  • Pulmonary – bronchodilators
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5
Q
  1. What is preload and when is it increased?
  2. What is afterload and when is it increased?
A
  1. **Preload: **Volume of blood in the ventricles at the end of diastole (end diastolic pressure)​
    • Increased in:
      • hypervolemia
      • regurgitation of cardiac valves
  2. Afterload: Resistance left ventricle must overcome to circulate blood
    • Increased in:
      • ​Vasoconstriction
      • HTN
      • Inc. afterload: Inc. cardiac workload
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6
Q

Organic Nitrates (2):

A
  • Nitroglycerin
  • Nitroprusside
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7
Q

Organic Nitrates:

Mechanism of Action

A
  • Nitric Oxide (NO) Donors
  • Intracellular Signaling:
    • Cyclic GMP/protein kinase G
  • Arterial and venous circulation (venous dominant)
    • Primarily affects preload
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8
Q

Nitroglycerine:

A
  • Relaxation of arterial and venous smooth muscle
    • Venous dominant
  • Treatment:
    • Heart Failure
  • Toxicity:
    • Hypotension
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9
Q

Nitroprusside:

A
  • Relaxation of arterial and venous circulations
  • Treatment:
    • Heart Failure
    • Hypertensive emergencies
  • Toxicity:
    • Hypotension
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10
Q

Direct Vasodilators (2):

A
  1. Hydralazine
  2. Minoxidil
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11
Q

Hydralazine:

A
  • Arterial circulation
  • Heart Failure
    • Affects afterload
  • Hypertension
    • Severe emergencies
  • Toxicity:
    • Hypotension
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12
Q

Minoxidil:

A
  • Severe HTN
  • K+ ATP Channel Opener
  • Arterial Circulation
  • Fluid Retention – Use with diuretics
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13
Q

Membrane Channel Dilators (2):

A
  • K+ Channel Activators
  • Ca2+ Channel Blockers
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14
Q

K+ Channel Activator - Diazoxide

A
  • K+ Channel Opener
  • Hypertensive Emergencies
  • Hypoglycemia
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15
Q

Membrane Channel Dilators – Ca2+ Channel Blockers

A
  1. Dihydropyridines – nifedipine
  2. Phenylalkylamine – verapamil
  3. Benzothiazapine – diltazem
  • Non-selective
  • Arterial circulation
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16
Q

Phosphodiesterase Inhibitors (2):

A
  • Phospodiesterase 3 Inhibitors
  • Phospodiesterase 5 Inhibitors
17
Q

PDE3 Inhibitors:

A
  • Milrinone, Inamrinone, Cilostazol
  • Prolong the action of cAMP
    • increased in the heart ⇒ increases contraction
    • vasodilator
  • Treatment:
    • Heart Failure
18
Q

Describe the effects of PDE3 inhibtors in heart vs. smooth muscle:

A
  1. Heart
    • inc. contraction
    • vasodilator
    • Phosphorylation of Ca2+ Channels - Inotropic
    • Phosphorylates Myofilaments - Inotropic
    • Phosphorylates K+ Channels
      • Repolarization - Chronotropic
  2. Smooth Muscle
    • Inhibits Myosin Light Chain Kinase
    • Phosphorylates K+ Channels
      • Hyperpolarization
19
Q

PDE5 Inhibitors:

A
  • Sildenafil, Tadalafil
  • Intracellular Signaling
  • Erectile Dysfunction
20
Q

Renin-Angiotensin Inhibitors:

Mechanism of Action

A

Angiotensin Converting Enzyme (ACE) Inhibitors

  • Enzymatic Pathway
  • Angiotensin Receptor / Intracellular Signaling
    • Angiotensin receptor blockers
    • Inihbit renin
  • Arterial (dominant) and Venous Circulation
21
Q

Miscellaneous Vasodilators (3):

A
  1. Bradykinin
  2. Fenoldopam
  3. Prazosin
22
Q

Bradykinin:

A
  • Powerful vasodilator
  • Interaction with the ACE Inhibitors
    • enhances vasodilation
  • Endothelial-derived Factors
    • B2 receptor
  • Arterial and venous circulation
23
Q

Fenoldopam:

A

Dopamine A1 Receptor Agonists

  • Arterial and venous circulation
    • increase RBF
    • increase Na+ excretion
  • Hypertensive Crisis
24
Q

Prazosin:

A

Alpha-adrenergic blocker

  • Arterial and venous circulation
    • vasodilation
25
Q

Bronchodilators (9):

A
  • ß2 agonists:
    1. ​​Albuterol
    2. Pirbuterol
    3. Terbutaline
    4. Salmeterol
    5. Formoterol
  • ​Anti-cholinergic:
    1. ​​Ipratropium
    2. Tiotropium
  • ​Methylxanthine:
    1. Theophylline
    2. Aminophylline
26
Q

Bronchodilators:

ß2 agonists

​​

A

Albuterol, Pirbuterol, Terbutaline, Salmeterol, Formoterol:

  • Intracellular Signaling
    • Cyclic AMP/protein kinase A
  • Cardiotoxicity
    • Tachycardia
27
Q

Bronchodilators:

Anti-cholinergic

A
  • Ipratroium, Tiotropium
  • Muscarinic Receptors
  • Mucous Secretion
28
Q

Bronchodilators:

Methylxanthine

A
  • Theophylline, Aminophylline
  • Phosphodiesterase Inhibition
  • Adenosine Receptor Antagonism
29
Q

Side effects of theophylline:

A
  1. decreased plasma exudation
  2. increased mucociliary clearance
  3. decreased neutrophil function
  4. decreased T-cell function
  5. decreased macrophage function
  6. increased respiratory muscle strength

PDA Block 2 (15 decks)

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