ABSTRACT
The 0 receptors are divided into 0i and 02. The 0i recep tors are located primarily in cardiac tissue and the kid neys. The 02 receptors mediate smooth muscle relaxation and are located in the vasculature, bronchi, and uterus (1). This is not absolute; 0i receptors are present in the lung, and a small number of 02 receptors are present in the heart (2,3). The 0i receptors are under the control of the neuro transmitter norepinephrine, which is released from the sympathetic neuron. The 02 receptors are not innervated and are under the control of circulating epinephrine.
