Effects of the Sympathetic Nervous System
The way in which beta-adrenergic blockers work is by decreasing workload and stress that the heart is under. This is done by specifically by blocking the beta 1 receptors which are located in the heart and receive signals (action potentials) from the adrenal gland that send out the hormone adrenaline..
Symptoms of the flight or fight response (sympathetic nervous system response)
When adrenaline is release and the sympathetic nervous system is activated, the body reacts by going into fight or flight mode. This mechanism is that it was great for human human survival when were running from bears and when the bear went away the sympathetic response went away. The problem with fight or flight today, is that it is activated in nonthreatening situations like bad traffic or even an overwhelming amount of work/homework.
How Beta-Adrenergic Blockers Work
Beta-adrenergic blockers decrease the sympathetic nervous systems response, which decreases the amount of adrenaline present in the body. With less adrenaline circulating through the body the veins dilate (widen), heart rate is slows and the force of contraction decreases all leading to a lower blood pressure. This also lowers the heart and body's oxygen demand helping to slow breathing.