Question

What are Alpha and Beta receptors? What do they respond to? Give examples of Beta blockers or Beta activator medications and relate the course content to describe how these medications can be used.

Answer 1

Alpha and beta receptors are the sympathetic or adrenergic type of receptors.

Aderenrgic receptors are the specific molecular structures in or on effector cells with which the catecholamines or symathetic drugs react in order to elicit various responses.

The adrenaline, nor adrenaline binds to these receptors to cause increase in the heart rate, blood pressure. Dopamine binds to the alpha 1 and 2 and beta 1 receptros.

Alpha receptors are of 2 types, type 1 and type 2-

Alpha Type 1- are the classic post synaptic alpha receptros that are found on the vascular smooth mucles. They detect and determine the arteriolar and venous capacitance and thereby blood pressure.

Alpha type 2- They are found in the brain and modulate the sympathetic outflow.

Beta receptors are of 3 types-

Beta type 1- They are found on the heart, where they are activated by the vagal nerve and cause an increase in the heart rate, contractility and untimately the cardiac output is increased, leading to increase in the blood pressure.

Beta type 2- these are located on the bronchi and bronchioles, they when activated cause bronchodilation and cause increase in the airflow into the lungs. and also present in the arteries of the skeletal muscle.

Beta type 3- These are found in the gall bladder urinary bladder and in brown adipose tissue. In the urinary bladder, they cause relaxation of the bladder and prevention of the urination and play a role in the lipolysis and thermogenesis in the brown adipose tissue.

Beta blockers-

Beta 2 blockers- atenolol, Carvedilol, Labetalol, metoprolol, Acebutolol, Timolol, Betaxolol - these are used in the treatment of the hypertension as when beta 2 receptors are blocked, the vagal stimulation is hindered and the heart rate, cardiac output and blood pressure is reduced.

Beta 1 agonist- Abuterol, terbutaline, levosalbutamol are the gourp of drgs which cause bronchodialtion and helps in ease of breathing in asthma and COPD conditions.

Beta 3 agonist- Mirabegraon is a drug which causes weight loss by increasing the lipolysis (using the stored fat up)

carvedilol which is an betaa 2 antagonist is also known to block the beta 3 receptor aswell.