Classify beta-blockers? What is the difference between selective and non-selective beta-blockers? How do beta-blockers affect heart rate and cardiac output?

  • Non-selective Beta blockers: Propranolol 
  • Selective Beta-1 blockers: Atenolol
  • Selective Beta -2 Blockers: Butaxamine 
  • Selective Beta-3 Blocker: SR 59230A

Difference between Selective & non-selective Beta blockers

The term, "Selective" means, these class of Beta blockers have affinity to bind with specific Receptors (Either Beta-1 or 2). For example, A Selective Beta-1 Receptor Blocker have only affinity towards Only a Beta-1 Receptor. 
Non-selective Beta blockers means, these agents have affinity towards all beta receptors (beta-, 2, or 3) and can bind to all these receptors and produces the pharmacological effect. 

How do beta-blockers affect heart rate and cardiac output?

Beta blockers are the Agents that binds with Beta receptor (Beta-1 especially in HEART) and blocks the endogenous Adrenaline and Nor-adrenaline to be bound with the Beta - 1 Receptor of heart. 
we know, adrenaline and noradrenaline are released by the Sympathetic nerve endings and by binding with beta -1 receptor results in increase in heart rate.
  • Heart Rate: Beta blocks slow down the Heart rate by blocking the beta - 1 receptor in the heart and prevent them to attach with Adrenaline which increases the HR.
  • Cardiac Output: Cardiac Output is the Vol. of blood heart pumps per minute. It is determined by Heart rate and Stroke Volume. Beta blocks slows the heart rate and Force of Contraction of Heart muscle and reduces the cardiac output. 

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