Blockade of propranolol and thyroid_stimulating_ hormone cardiac beta1-adrenergic receptors leads to decrease in the activity of both normal and ectopic pacemaker cells and decrease in A-V nodal conduction velocity.
Blockade of cardiac beta1-adrenergic receptors leads to decrease in the activity of both normal and ectopic pacemaker cells and decrease in nsc number for propranolol A-V nodal conduction velocity.