Stop using Cialis and get emergency medical help if you have: erection is painful or lasts longer than 4 hours (prolonged erection can damage the penis); vision changes or sudden vision loss; or. heart attack symptoms - chest pain or pressure, pain spreading to your jaw or shoulder, nausea, sweating.
For example, we now know that several areas in the brainstem and hypothalamus promote wakefulness by sending arousal signals to the cerebral cortex, the brainâs largest region. These signals come in the form of chemicals called neurotransmitters. When neurons in the arousal areas are active, the cortex remains activated and we stay awake. One area of the brain that promotes arousal is the tuberomammillary nucleus (TMN). Here, neurons release histamine as one of their neurotransmitters. Interestingly, many  anti-histamine  medicines block this arousing signal and cause sleepiness.
Brain activation and sexual arousal. Brain, Vol. 125, No. 5, 1014-1023, May 2002. Brain activation and sexual arousal in healthy, heterosexual males. Bruce A. Arnow, John E. Desmond, Linda L. Banner, Gary H. Glover, Ari Solomon, Mary Lake Polan, Tom F. Lue and Scott W. Atlas. Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, Calif., USA. (paraphrase).