To understand beta-blockers, we must first know what beta-receptors are, what they do and why they need to be blocked by the beta-blockers for heart patients.
In very simple terms, beta-receptors are protein molecules that help process various messages emanating from the central nervous system to all the organs, tissues, cells etc. To be able to be effective towards this function, beta-receptors are dispersed throughout our body, but are found more in some parts.
There are 3 types of beta-receptors, beta-1, beta-2 and beta-3. Beta-1 is primarily found in our heart and kidneys. Beta-2 is found in higher concentrations in our lungs, skeletal muscles, liver, gastro-intestinal tract, uterus, smooth cardio vascular muscles etc and Beta-3 is found mainly in the fat cells of our body.
Under situations of stress, anxiety, excitement or heart dysfunction, the adrenaline (aka epinephrine) released by our adrenal glands stimulates all the beta-receptors (beta-1, beta-2 and beta-3) and makes us ready for a fight-or-flight response.
Stimulation of beta-1 receptor sets-off a chain of changes such as increasing our heart rate, increasing the force of heartbeat, increasing the automacity of the heart, increasing the volume of blood pumped out per beat. It also excites the kidney to release renin and this increases our blood pressure.
Agitation of beta-2 receptors by adrenaline causes tremors in our skeletal muscles, increase in glycogenolysis (which produces a complex compound of glucose and phosphate that enables lightning speed delivery of energy) by the liver and smooth muscles, increase in gas exchange through the alveoli of the lung and increase in the smooth muscle relaxation.
Stimulation of beta-3 receptors by adrenaline causes breakdown of fat cells and release of free fatty acids and ketones.
High adrenaline release consistently keeps body on it’s toes and though this is a desired state in times of emergency and could make the difference between life and death, being in this state for prolonged periods for healthy individuals and especially for heart patients is disastrous for obvious reasons.