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When many people look at sexual images, they often can become sexually aroused, including full genital arousal, and feel urges, known more often used as "horny" as slang/urban usage.

How does this process work in males and females? Is it different in males than in females, or is the network the same between the eyes and the brain, down to the genitals as a precursor to masturbation, sex, etc.? Also, what exactly happens in the brain before it tells the genitals to get horny or such? Examples would be in viewing porn, naughty images/pics, etc.

Men and women and girls and boys alike can get full arousal from this. How does the process work?

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closed as too broad by Chris, The Last Word, WYSIWYG, jonsca, fileunderwater May 30 '15 at 16:00

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ This is not opinion based. It is a little broad though. Please edit your question; if it can be worded properly then it is on topic. $\endgroup$ – WYSIWYG May 28 '15 at 5:38
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Sexual arousal is a very complex response, that includes a whole range of physiological changes, firing of lots of neural pathways, increased muscle tension, elevated heart rate with increased blood flow to the skin, primary and secondary sexual organs and a whole lot of hormonal spikes.

Sexual desire is defined as the behavioural drive that motivates individuals to fantasize about or seek out sexual activity. In contrast, sexual arousal is defined as the autonomic physiological processes that prepare the body for sexual activity (Toledano, Pfaus., 2006).

The brain is rightfully regarded as the largest sexual organ, with most of the pleasure arising from the limbic system of the brain (which interestingly enough, is common to all mammals regulating emotion and encouraging the avoidance of painful of aversive stimuli and the repetition of pleasurable experiences).

From a physiological perspective sexual arousal is controlled by the parasympathetic portion of the autonomic nervous system and manifests itself as vasodilation in sexual organs along with several other physiological phenomena including an increase in heart rate. An orgasm and in particular male ejaculation is controlled by the sympathetic portion, this is also accompanied by deactivation of many areas in the brain relating to external stimuli in particular fear, allowing the mind to focus on the task at hand.

Now it is a bit long to go into the details of the sexual response cycle, and hence here is a brief summary:

Neural pathways:

Prior to the physical stimulation, comes sexual desire. Largely mediated by emotion through the limbic system, activation of the amygdala can trigger penile erection, sexual feelings,(Georgiadis and Holstege, 2005) sensations of extreme pleasure (Olds and Milner, 1954), memories of sexual intercourse (Gloor, 1986), as well as ovulation, uterine contractions, and orgasm.

The amygdala is sexually differentiated part of the brain that is known to produce sex specific responses. In short the amygdala has a pathway (amygdalofugal pathway) that connects with the major regions of the brain that regulates sexual feelings. An increased density of enkephalins and opiate receptors can be also found in amydala, which induces extreme feelings of pleasure.

interestingly...

Males more then females, were found to have greater amygdala activation when presented with a sexually pleasing, visual stimuli (Hamann et al., 2004).

Moving on, other areas of the brain implicated in sexual arousal are...

Input travels from the basolateral nuclei of the amygdala along the amygdalofugal pathway to the ventral striatum, made up of the nucleus accumbens, putamen and parts of the caudate nucleus. The nucleus accumbens plays a role in pleasure and reward due to a large large of dopaminergic neurons from the VTA (ventral tegmental area).

The Vagus nerve is known to lead to the Nucleus Tractus Solitarii (NTS) in the Medulla Oblongata. Following this stimulation of the brain via the vagus nerve during orgasm there was a difference in activity between preorgasm and orgasm. Areas of activation during and after orgasm include the hypothalamic paraventricular nucleus (PVN), midbrain central gray, amygdala, hippocampus, anterior cingulate, frontal, parietal, temporal and insular cortices, anterior basal ganglia, and cerebellum (Whipple, 2008). Although this may be the explanation for female orgasms, there is no evidence to suggest that this is the case for males.

Hormonal changes: I am not going to write too much about this as this information is readily accessible in the net. Sexual arousal causes the cerebral cortex to signal the hypothalamus to stimulate the production of testosterone, the production is regulated by a complex chain of events known as the hypothalamic-pituitary-gonadal axis, which ultimately causes the pitutary gland to release luteinizing hormone which signals the testes to produce testosterone and ovaries to produce oestrogen.

You can read more here: http://neurosciencefundamentals.unsw.wikispaces.net/Sex+and+the+Brain.+What+parts+are+involved%3F

For an in-depth analysis I recommend this book: Greenberg, Jerrold S., Clint E. Bruess, and Sara B. Oswalt. Exploring the dimensions of human sexuality. Jones & Bartlett Publishers, 2014.

This is a good review for endocrinology in sexual arousal: Bancroft, J. "The endocrinology of sexual arousal." Journal of Endocrinology 186.3 (2005): 411-427.

As usual, wikipedia also covers a few models of sexual arousal (Singer, Basson's etc..) that I have not mentioned here: http://en.wikipedia.org/wiki/Sexual_arousal

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