Question

Short / Long answer type questions.
What types of adrenergic receptors are present in different tissues and how do they function?

Answer 1

The autonomic nervous system has two main receptors types: the cholinergic receptors and the adrenergic receptors. The adrenergic receptors are those that are acted upon by natural biochemicals found in your body called epinephrine and norepinephrine. The adrenergic receptors are divided into two types: alpha and beta.

The alpha receptors, or alpha-adrenoceptors, are those that respond to epinephrine and norepinephrine. The alpha receptors are divided into two different kinds as well: alpha 1 and alpha 2.

When stimulated, the alpha 1 receptors are largely responsible for:

• Vasoconstriction: constriction of the blood vessels. 'Vaso-' refers to blood vessels. Stimulation of alpha 1 receptors helps to constrict the blood vessels. As a result of this, blood pressure will go up.
  
• Mydriasis: dilation of the pupil.
  
• The contraction of the internal sphincter of the bladder, preventing the flow of urine.
  

When the alpha 2 receptors are stimulated, this can cause:

• The suppression of norepinephrine release.
  
• The suppression of the acetylcholine release. Acetylcholine is the biomolecule that acts on cholinergic receptors.
  
• The inhibition of insulin release. Insulin is the molecule that helps send glucose into your body's cells.

Beta receptors, or beta-adrenoceptors, are divided into three types: beta 1, beta 2, and beta 3 receptors.

Stimulation of beta 1 receptors leads to:

• Tachycardia: a fast heart rate
  
• Increased breakdown of fat
  
• Increased strength to the heart's contraction
  
• Increased release of renin, a compound which helps to ultimately increase blood pressure
  

When beta 2 receptors are stimulated, the following can be expected:

• Vasodilation, or the widening of blood vessels.
  
• Bronchodilation and an increase in glucose in the bloodstream.

Stimulation of beta 3 receptors causes -

• breakdown of fat.
• relaxation of the urinary bladder.
• generation of body heat.