Give other examples of disturbances in the internal environment that can act as a stimulus.
> An example is when the blood pressure is too high. The arteries will stretch as a result of increased blood pressure, and receptors will then signal the brain. The heart rate will be reduced by the brain. If the receptor is not signaling, the blood pressure is likely low. To maintain a normal blood pressure, the brain will speed up the heart rate. All of this occurs without of any noticeable warnings. Humans, however, experience pain at the back of the head when blood pressure is too high.