In response to electrical stimulation of a particular brain region, a rat shows increased blood pressure and heart rate, dilation of the pupils, erection of the hair on the back, arching of the back, and biting at the air. Which region could the electrode be stimulating

The brain stem is responsible for increased blood pressure, HR etc,

Explanation:

It is made up of the mid brain, the Pons, and the Medulla.

While the Pons serve as the neurological bridge between the brain regions e. g the cerebrum and cerebellum to conduct and control certain responses the Medulla controls involuntary activities. Thus the involuntary activities listed above are controlled by the medulla.

Thus the activities of the rats which involves the dilation of pupils, erection of hair, are controlled in the pons. While increases blood pressure and the H. R are under the medulla.