Alpha Receptors:
- Generally found on smooth muscle cells.
- Subtypes: α1 and α2.
- α1 receptors primarily mediate smooth muscle contraction.
- α2 receptors mostly inhibit neurotransmitter release, leading to relaxation of smooth muscle.
Beta Receptors:
- Predominantly located on cardiac muscle cells and some smooth muscle cells.
- Subtypes: β1, β2, and β3.
- β1 receptors primarily stimulate cardiac muscle contraction and increase heart rate.
- β2 receptors mainly induce smooth muscle relaxation, particularly in bronchi and blood vessels.