Or more precise: it is what you feel as you anticipate (or imagine) having sex.
Anticipation is the key word as sexual desire is wanting, craving and wishing for sex.
In other words, libido is the mechanism that motivates you to have sex.
It drives you to have sex because your brain wants to pass on your genes to the next generation.
More About Libido
Desire for sex, or libido, is normally set off by some sort of sexual stimulation. This can be a visual observation (hot girl walking down the street), it can be a touch or other sensory stimulation, it could be a thought or a sexual fantasy, etc.
This stimulation (for instance that hot woman walking by you) causes dopamine to be produced in your brain. Dopamine then sets off a chain reaction of events that eventually causes blood to flow into and fill your penis.
Some men have an overall strong sex drive, meaning that it takes very little stimulation to set in motion the urge for sex, and that this happens very frequently.
Other men have a weak sex drive, which means it takes a lot of stimulation for them to get in the mood for sex.
The degree of your sex drive is to a very large degree determined by your testosterone levels.
Testosterone is the primary male sex hormone that underlies and controls everything sexual that goes on in your body. With large amounts of testosterone you will normally be highly sexually charged (high libido), and with low levels of testosterone you will normally have a low libido.
People normally differ in the degree of their sex drive.
Libido differs not only from person to person, but also in the same person from one day to the next, as well as over one’s life span.
For instance, you have probably had periods in your life where you had a super high sex drive. And you have probably had periods where you had very little interest in sex and where your libido was almost non-existent.
So what is it that causes libido to vary so much?
What Causes Your Libido To Fluctuate?
In addition, when you stress, your brain channels attention away from your sexual organs and to those parts of your body that are useful for the stressful situation (large muscle groups, vision, etc.).
If you are depressed, sad, anxious or have psychological problems, you may also have a lower libido as this also simply fills your mind with negative thoughts and leave less space for thinking about and craving sex.
If you watch pornography and masturbate a lot, you are also likely to have a lower libido. This is because you then are in danger of desensitizing your brain to sexual stimulation.
By watching porn and masturbate, you also satisfy your brain’s need for sex. Now your brain craves less sex.
In addition, libido can be influenced by one or more particular personal experiences you may have had in life, for instance one related to sex or physical abuse.
The culture you grew up in and its norms, rules and customs can also impact the level of your libido. The same goes for religious believes.
But why do we have this libido? What is the purpose of it?
What Is The Purpose Of Libido?
The role of libido is to motivate us to procreate – to create new life and thereby sustain the life of the species.
Or put differently:
The evolutionary mechanism of libido is to drive us to have sex in order to pass on our genes to the next generation so that life is continued.
If we didn’t have a libido, we would have less sex, and also less offspring.
So when you see a hot woman at the party and your head starts going a bit crazy about her, it’s your libido telling you to have sex with her. Hopefully, you won’t approach her and try to take her clothes off, but that is essentially what your brain wants you to do.
And this libido has evolved and become amplified in us through millions of years.
Those individuals who in the past had the strongest sex drive, probably had more offspring than other individuals. And hence, individuals with this trait (a strong sex drive) were selected by evolution through ‘survival of the horniest’.
But not only that, libido is also normally very important for your life quality.
Libido And Quality Of Life
In other words, a healthy and normal sex drive is something that brings happiness and satisfaction to most people.
When libido is reduced or non-existent, this can often be an indication of impaired health. Therefore, a person with no libido is also likely to also have other, and potentially more dangerous, health issues.
The Mechanisms Behind Libido
Although one may think everything related to sexual desire happens between the legs, the experience of this desire actually occurs in the brain.
In fact, all thoughts, feelings, and bodily sensations correlate with specific nerve cells being activated in the brain.
The initial urge for sex as well as the euphoric and pleasurable experience of sex itself stems primarily from the limbic system, which encompasses various parts of the brain such as the amygdala, hippocampus and limbic lobe.
This area is common to all mammals and is considered one of the oldest areas of the brain. It regulates emotion, motivation, pleasure, reward as well as other functions.
When the brain detects some form of sexual stimulation (for instance a sensual touch), nerve cells in one part of the limbic system send signals to another part of the limbic system where motivation, urge and craving are generated.
This is how libido is kicked off.
Dopamine will normally also cause the heart rate to increase when you experience this desire for sex. Some people may also experience a blood pressure increase, breathing becoming more rapid, cheeks that flush or palms that get sweaty.
Let’s say you’re sitting on a crowded bus watching a very attractive woman. You may get excited for a little, but the situation is not conducive to anything but imagination and fantasies, and hence your libido will probably die down soon after seeing her.
Let’s instead say that you are at home and your girlfriend comes home from work. You chat for a little, she touches you, you kiss and you get excited.
In this situation, this may lead to sex. So what would normally happen next is that you get an erection and you proceed to having intercourse.
I mentioned testosterone before..
What if you have a low libido?
Bancroft J. The endocrinology of sexual arousal. J Endocrinol. 2005 Sep;186(3):411-27.
Brunetti M, Babiloni C, Ferretti A, Del Gratta C, Merla A, Olivetti Belardinelli M, Romani GL. Hypothalamus, sexual arousal and psychosexual identity in human males: a functional magnetic resonance imaging study. Eur J Neurosci. 2008 Jun;27(11):2922-7. DOI: 10.1111/j.1460-9568.2008.06241.
Dominguez J, Riolo JV, Xu Z, Hull EM. Regulation by the medial amygdala of copulation and medial preoptic dopamine release. Journal of Neuroscience. 2001;21:349–355.
Dominguez JM, Hull EM. Stimulation of the medial amygdala enhances medial preoptic dopamine release: implications for male rat sexual behavior. Brain Research. 2001;917:225–229.
Dominguez JM, Muschamp JW, Schmich JM, Hull EM. Nitric oxide mediates glutamate-evoked dopamine release in the medial preoptic area. Neurosci 2004; 125: 203-210.
Du J, Lorrain DS, Hull EM. Castration decreases extracellular, but increases intracellular, dopamine in medial preoptic area of male rats. Brain Research. 1998;782:11–17.
Everitt BJ. Sexual motivation: a neural and behavioural analysis of the mechanisms underlying appetitive and copulatory responses of male rats. Neurosci Biobehav Rev 1990; 14: 217-232.
Giuliano F, Allard J. Dopamine and sexual function. Int J Impot Res. 2001 Aug;13 Suppl 3:S18-28.
Gray PB, Garcia JR. Evolution & Human Sexual Behaviour, Harvard University Press, 2013.
Hackney AC, Lane AR, Register-Mihalik J, Oʼleary CB. Endurance Exercise Training and Male Sexual Libido. Med Sci Sports Exerc. 2017 Jul;49(7):1383-1388. DOI: 10.1249/MSS.0000000000001235.
Halaris A. Neurochemical aspects of the sexual response cycle. CNS Spectr. 2003 Mar;8(3):211-6.
Hansen S. Hypothalamic control of motivation: the medial preoptic area and masculine sexual behavior. In Sodersten P, editor. Behavioral neuroscience in Scandinavia. Scandinavian Journal of Psychology 1982; Suppl 1: 121-126.
Holloway V, Wylie K. Sex drive and sexual desire. Curr Opin Psychiatry. 2015 Nov;28(6):424-9. DOI: 10.1097/YCO.0000000000000199.
Hull EM, Du J, Lorrain DS, Matuszewich L. Extracellular dopamine in the medial preoptic area: implications for sexual motivation and hormonal control of copulation. Journal of Neuroscience. 1995;15:7465–7471.
Karama S, Lecours AR, Leroux JM, Bourgouin P, Beaudoin G, Joubert S, Beauregard M. Areas of brain activation in males and females during viewing of erotic film clips. Hum Brain Mapp 2002, 16:1–13.
Krüger TH, Hartmann U, Schedlowski M. Prolactinergic and dopaminergic mechanisms underlying sexual arousal and orgasm in humans. World J Urol. 2005 Jun;23(2):130-8.
McKenna K: Central nervous system pathways involved in the control of penile erection. Annu Rev Sex Behav 1999, 10:157–183.
Meisel RL, Sachs BD: The physiology of male sexual behavior. In The Physiology of Reproduction, Second Edition. Edited by Knobil E, Neill JD. New York: Raven Press; 1994:3–105.
Motofei IG, Rowland DL. The physiological basis of human sexual arousal: neuroendocrine sexual asymmetry. Int J Androl. 2005 Apr;28(2):78-87.
Mouras H, Stoléru S, Bittoun J, Glutron D, Pélégrini-Issac M, Paradis AL, Burnod Y. Brain processing of visual sexual stimuli in healthy men: a functional magnetic resonance imaging study. Neuroimage. 2003 Oct;20(2):855-69.
Pfaus JG, Scepkowski LA. The biologic basis for libido. Current Sexual Health Reports 12/2005; 2(2):95-100. DOI: 10.1007/s11930-005-0010-2.