Final answer:
The autonomic nervous system has two types of adrenergic receptors, alpha and beta adrenergic receptors, that bind to the neurotransmitters norepinephrine and epinephrine. These receptors elicit different responses in target cells.
Step-by-step explanation:
The autonomic nervous system has two types of adrenergic receptors, the alpha (α)-adrenergic receptors and the beta (β)-adrenergic receptors.
The alpha-adrenergic receptors include α₁, α₂, and α₃. These receptors bind to the neurotransmitters norepinephrine and epinephrine.
The beta-adrenergic receptors include β₁ and β₂. These receptors also bind to norepinephrine and epinephrine. Additionally, there is a β₃-adrenergic receptor, which is primarily found in adipose tissue and plays a role in regulating fatty acid metabolism.
When the neurotransmitters bind to these receptors, they elicit different responses in the target cells. For example, activation of α₁-adrenergic receptors leads to vasoconstriction of blood vessels and increased smooth muscle contraction, while activation of β₁-adrenergic receptors increases heart rate and contractility.