The libido key for sexual activity fuel of psychic energy, regulated by sex hormones and neurotransmitters. Hypoactive sexual desire disorder, affects 10% or 6 million premenopausal women in USA. Freud: libido, energy found in the Id, the unconscious structure of the psyche, has phases in toddlers: Oral stage, Anal stage, Phallic stage, Genital stage in adults. Jung: libido is the totality of psychic energy. Psychological factors reduce the desire for sex: lack of privacy, stress , depression, sexual abuse. Posttraumatic Stress Disorder: decreased brain activity in areas of emotion. Libido is...

Autonomic nervous system has sympathetic (SNS), parasympathetic (PNS), enteric nervous system (ENS) that regulate the body's unconscious actions, the body's fight or flight response, and the body to feed and breed. SNS signals travel by preganglionic neurons that release acetylcholine (ACh), activating nicotinic ACh receptors on postganglionic neurons releasing norepinephrine that activates adrenergic receptors (AR) on peripheral tissues. SNS: accelerate heart rate; widen bronchial passages; decrease motility of large intestine; constrict blood vessels; increase oesophagus peristalsis; cause...