Physiology of ejaculation

The physiology of normal ejaculation is a complex reflex response to neurobiological and neurobiochemical stimulation. Neurological regulation of the male human sexual response occurs in the brain and in the thoracolumbar and sacral segments of the spinal cord. The neurotransmitters dopamine and serotonin play a major role in controlling the ejaculatory reflex. Serotonin, acting on 5-HT receptors, is the principal neurotransmitter that inhibits ejaculation; the brain's level of serotonin usually corresponds to a man's ejaculatory latency. Neurons controlled by other chemicals, such as adrenaline, acetylcholine, oxytocin, and aminobutyric acid, may also contribute to the ejaculatory process.

Orgasm, a pleasurable sensory experience perceived in the brain, usually accompanies ejaculation in the male; orgasm can occur, however, without erection, emission, or ejaculation. Orgasm may also be absent. Following ejaculation, the male loses his erection and goes through a refractory period, during which no penile tumescence can occur. Depending on his age and other biological and psychosocial factors, and with renewed sexual stimulation, he will then be able to achieve a new erection within a few minutes, hours, or days.