Alpha vs Beta Receptors: Difference and Comparison

Adrenergic Receptors are a classification of G-protein receptors sensitive to our body’s neurotransmission and target many catecholamines produced by the body.

These receptors help our body to regulate responses to certain stimulators. These adrenergic or adrenoceptors are of two types: Alpha Receptors and Beta Receptors.

Key Takeaways

  1. Alpha receptors are responsible for vasoconstriction and increasing blood pressure, while beta receptors are responsible for vasodilation and decreasing blood pressure.
  2. Alpha receptors are found primarily in smooth muscle cells of blood vessels, while beta receptors are found primarily in the heart and lungs.
  3. Alpha receptors are stimulated by the hormone epinephrine, while beta receptors are stimulated by both epinephrine and norepinephrine.

Alpha vs. Beta Receptors

Alpha receptors are a type of adrenergic receptor cells that release epinephrine and nor epinephrine and are involved in the contraction of the smooth muscles. Beta receptors are another kind of adrenergic receptor cells and assist in relaxation of heart, lungs, and uterine muscles.

Alpha vs Beta Receptors
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Alpha Receptors are one of the two types of adrenergic receptors. They are again subdivided into Alpha1 and Alpha2 receptors. These receptors are located on the arteries or at the postsynaptic area of our organ’s sympathetic neuroeffector in the splanchnic vessel contraction.

Beta receptors are another type of adrenergic receptor located postsynaptically in our organs. These receptors are again subdivided into Beta1, Beta2, and Beta3 Receptors.

When these Beta receptors are activated, the muscles of our body relax. The common activity of these receptors is an increase in heart rate, lipolysis, and renin release.

Comparison Table

Parameters of ComparisonAlpha ReceptorsBeta receptors
DefinitionAlpha Receptors are the Adrenergic Receptors that control physiological processes like intestinal relaxation and vasoconstriction.Beta Receptors are a class of receptors that control the relaxation of bronchial, vasodilation, and increased heart rate.
ActivityIt stimulates effector cellsIt relaxes effector cells.
FunctionIt is responsible for blood vessel contraction.It is responsible for the dilation of the blood vessels.
LocationIt is located in the vascular smooth muscles and effectors tissue.It is located in the bronchial, uterine, and heart muscles.
TypeThere are two types of Alpha Receptors, namely Alpha1 and Alpha2 Receptors.There are three types of Beta receptors, namely Beta1, Beta2, and Beta3 receptors.

What are Alpha Receptors?

Alpha Receptors are a group of receptors.

They are located on the cell surface of some effectors tissue or organs innervated by the sympathetic nervous system that mediates certain physiological responses such as relaxation of intestinal muscles, vasocontraction, and contraction of smooth muscles.

These Receptors are subtypes of Adrenergic Receptors which are involved in regulating responses in certain stimulators in our body. Alpha Receptors are of two types, namely Alpha1 Receptors and Alpha2 Receptors.

The use of these receptors depends on the medication that indicates the targeted respondent’s organs. The Alpha1 receptors are most commonly used in shock, heart failure decompensation, and cardiopulmonary resuscitation.

Alpha1 receptors are again subdivided into Alpha1 agonists and Alpha1 blockers. Alpha2 Receptors are used off-label for the treatment of post-traumatic stress disorder.

Their stimulation reduces the outflow of the sympathetic nervous system from the vasomotor center and increases vagal tone. Sometimes these receptors also reduce sympathetic tone. It includes clonidine and guanfacine, which are used as antihypertensives.

They are of two types, namely Alpha2 Agonists and Alpha2 Blockers. Between 1906 and 1913, Henry Hallett Dale explored the effect of adrenaline on animals. He injected it into the vessels, which increased the blood pressure of these animals.

He also exposed these animals to ergotoxine, which decreased blood pressure. After these experiments, he proposed ergotoxine caused a fall in blood pressure and selective paralysis of smooth muscles.

He added that these components either cause contraction or relaxation depending on the responses of different junction types to the same component. In the 20th century, it was agreed that stimulating sympathetic nerves causes different effects on body organs.

They made two proposals to explain the phenomenon. There were two types of neurotransmitters released from nerve terminals; secondly, there were two types of detectors mechanisms. Arturo Rosen and Walter Bradford Cannon introduced this hypothesis.

What are Beta Receptors?

Beta receptors are a group of receptors on the surface of the cells, specifically located on some effector tissue and organs innervated by the sympathetic nervous system.

These receptors mediate certain physiological responses such as relaxation of the bronchial, vasodilation, increased heart rate, and uterine smooth muscles. These receptors are subtypes of Adrenergic Receptors subdivided into three different receptors, namely Beta2, Beta2, and Beta3 Receptors.

Bet1 Receptors are essential components for the normal physiological function of the Sympathetic nervous system. These receptors are activated through various hormones, medications, or signaling mechanisms.

Beta2 receptors are cell membrane-spanning adrenergic receptors. They activate g-protein-coupled receptors that bind norepinephrine and epinephrine. Beta3 receptors are in the urinary bladder, brown adipose tissue, and gallbladder. It relaxes the bladder and prevents urination.

Main Differences Between Alpha and Beta Receptors

  1. Alpha Receptors are the Adrenergic Receptors that control physiological processes like intestinal relaxation and vasoconstriction. Beta Receptors are a class of receptors that control the relaxation of bronchial, vasodilation, and increased heart rate.
  2. Alpha Receptors stimulate effector cells, whereas Beta Receptors relax effector cells.
  3. Alpha Receptors are responsible for the contraction of blood vessels. On the other hand, beta receptors are responsible for the dilation of the blood vessels.
  4. Alpha Receptors are located in the vascular smooth muscles and effectors tissue, whereas beta receptors are in the bronchial, uterine, and heart muscles.
  5. There are two types of Alpha Receptors, namely Alpha1 and Alpha2 Receptors. , Beta Receptors are of three types, namely Beta1, Beta2, and Beta3 receptors.
References
  1. https://europepmc.org/article/med/6253412
  2. https://www.sciencedirect.com/science/article/pii/0024320577900662
  3. https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/j.1749-6632.1967.tb41229.x

Last Updated : June 11th, 2023

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