Your nervous system responds to both mental and physical stimulation to enhance arousal, penile firmness, and orgasm. Common neurological problems include disorders like multiple sclerosis, effects of diabetes and other untreated or poorly controlled illnesses, medication side effects, alcohol and drug abuse, and physical injury to the penis. Psychological, relational, and situational factors can also inhibit neurological function.
The nerves involved in this process connect the lower spine to the penis via the pelvic nerve, which branches into the cavernous nerve that manages the three spongy cylinders of the penis. The importance of these nerves is evident when damage occurs during prostate or rectal surgeries, causing postsurgery neurologic injury.
An erection is a neurological reflex involving the spinal cord and brain. The spinal reflex causes relaxation of the penile smooth muscle, causing dilation of the penile arteries, resulting in an erection. Higher central nervous system areas in the brain (e.g., hypothalamus and amygdala) are involved in obtaining and maintaining erections as well as triggering ejaculation and the pleasure of orgasm.