Final answer:
The heart is the organ that has only beta 1-receptors.
Step-by-step explanation:
The organ that has only beta 1-receptors is the heart.
Beta 1-receptors are a subtype of beta-adrenergic receptors. These receptors are found in various organs throughout the body and play a role in regulating heart rate and blood pressure. In the heart, beta 1-receptors are specifically responsible for increasing heart rate and contractility.
The liver, bladder, and pancreas do not have exclusive beta 1-receptors.