Human sexuality has diversified into an all-encompassing stratum over the course of time.
People, now, are able to get psychological and sociological representation of self in terms of their sexuality and orientation. But if you ask, is that why they display particular behavior during sexual intercourse?
It’s a bit complicated.
Men and women have several differences when it comes to sexual responses. Our social settings play a huge role in determining our behavior. And so does our biological system.
The mechanism of sexual behavior is co-dependent on many such factors. So, how do you explain it? Read on to find out!
What does history say?
Sexual reproduction is the norm and it has evolved repeatedly on Earth.
We all are aware that sexual activity is performed by almost all living species. Furthering the existence of the species being the prime motive, the act of intercourse is definitely not something that requires to be taught. The instinct is inherent.
There is no denial that apes are our brethren species. Studies say that their sexual behavior can be observed most frequently around the time when the female is ovulating. They are even capable to appropriate their mating behavior based on their mate’s dominance rank or other aspects of social context with great flexibility.
What does it say? Sexual behavior is also subject to evolution and it can be co-opted for other purposes. In this case with the apes, the males prompt sexual engagement in order to establish dominance in the multigenerational female system. And guess what? They even managed to adapt sexual activity for alleviating boredom or simply pleasure.
That sure does explain why even humans enjoy sex besides the primeval responsibility of reproducing. But what happens inside the human body when one is tempted to have sex?
Mechanism of sexual behavior: The modern perspective
Researching the physiological mechanisms that underlie sexual behavior in humans has always been tricky. Much of what we know today comes from animal research. 
From the evidence in both preclinical and clinical studies over the years, the process and initiation of sexual arousal are found to have a more lucid basis. Sexual arousal is dependent on neural systems (sensory and cognitive), hormonal stimulations, and genetic factors.
Sexuality is more of motivated behavior.  However, one can be aroused and motivated to display sexual behavior only in special environmental situations by providing particular types of sensory stimulations. As soon as the body receives these sensory signals, hormones jump into action which then controls the course of neural and non-neural mechanisms throughout the body.
In the year 1966, a book was published by William Masters and Virginia Johnson detailing their observations for the study of physiological responses during sexual behavior. Participants of the study were observed having intercourse in various positions and masturbating, manually or by using any device.
Based on their observations, the researchers divided the sexual response cycle into four phases that are similar in both men and women: Excitement, Plateau, Orgasm, and Resolution.
- The Excitement phase is the arousal phase in which the penis or clitoris erects and the vaginal canal expands.
- In the Plateau phase, there is further swelling of the vagina and increased blood flow to the labia minora for women. While men experience full erection and often exhibit pre-ejaculatory fluid.
- The Orgasm phase in women is marked by the rhythmic contraction of the pelvis and uterus along with increased muscle tension. For men, pelvic contractions are accompanied by a buildup of seminal fluid near the urethra which is ultimately forced out by contractions of the genital muscles.
- Resolution is the relatively rapid return to an unaroused state accompanied by a decrease in blood pressure and muscle relaxation. 
Apparently, the studies on sexual arousal in women were very rare than studies involving men. Researchers observe that this discrepancy could be due to difficulty in establishing the significant correlation between physiological and subjective arousal in women. Also, male genital arousal is easier to notice than female genital arousal. 
Anyways, researches are in progress and hopefully, we can learn more about female sexual behavior soon!
Brain and neurochemical basis of sexual background
The hypothalamus has a major role in activating motivated behaviors. Sexual activity being a process that involves attraction, motivation, and performance, the hypothalamus is indirectly involved. It stimulates the production and secretion of Testosterone, thereby ensuring sexual receptivity in males.
But sexual behavior isn’t orchestrated by a one-man army. Researchers say that it is controlled by multiple areas across the brain and spinal cord. While the Central Nervous System (CNS) corresponds to the motivational components, the Peripheral Nervous System tends to the purely voluntary behavior including erection and ejaculation.
Studies show that the interaction of five major neurochemically distinct systems are responsible for increasing sexual arousal. The transmitters include norepinephrine, dopamine, serotonin, acetylcholine, and histamine. But you don’t have to worry about each of their functions. Let’s focus on the basic process.
The most widely endorsed hypotheses suggest that dopamine plays an excitatory role in sexual behavior and serotonin an inhibitory role. The increase in the activity of dopaminergic systems always correlates with sexual activity. The male sexual response reflects a dynamic balance between these exciting and inhibiting forces.
On receiving sensory signals, the so-called erotic stimuli, sexual excitation is evoked in the sensory system, limbic system, hypothalamus, and autonomic nervous system.  The medial preoptic area, located at the anterior of the hypothalamus, elicits male sexual behavior. When one is aroused either by sight, touch, or external stimulation of the genitalia, excitatory signals originate in the brain. The cerebral cortex then sends signals to initiate motor responses. 
This sexual excitation also travels to the spinal cord and starts a series of autonomic reflexes (both parasympathetic and sympathetic) which are responsible for controlling selective blood afflux to these regions, secretion of glands, and contraction of muscles in the sexual organs. Dopamine transmission increases sharply in the nucleus accumbens in the hypothalamus during copulation. This facilitates the release of pro-erectile neurotransmitters like Nitric Oxide(NO) and acetylcholine which signals the smooth muscles of the penile arteries to relax and fill with blood resulting in an erection. 
Simultaneously, the sensorial impulses also travel up to the brain to the sensory cortex and the limbic system (the emotional brain) where they elicit conscious perception and pleasurable emotional reaction.
Isn’t it amazing how the things we feel in the split of a second are a result of elaborate mechanisms in our body?
More about Nitric Oxide’s role in sexual behavior
Nitric Oxide (NO) is a retrograde neurotransmitter in the synapses. It has been implicated in diverse physiological functions.
Recent studies suggest that NO is a major physiological stimulus that helps in the relaxation of penile vasculature and muscles which are essential for erection. It also mediates the vasodilation in the nerves responsible for penile engorgement and erection. 
The paraventricular nucleus of the hypothalamus contains the cell bodies of a group of oxytocinergic neurons extending to certain areas of the brain and spinal cord, which are responsible for the control of erectile function during copulation. The activation of these paraventricular oxytocinergic neurons by dopamine and other hormones is mediated by the activation of Nitric Oxide (synthase). 
This NO synthase, in turn, activates the release of Oxytocin from oxytocinergic neurons in the extrahypothalamic brain areas. Oxytocin, yes, the same hormone that stimulates uterine contractions during labor as well as the release of milk during breastfeeding, is an important neurotransmitter in men which contributes to the production of pro-erectile pathways. 
Nitric Oxide acts as a physiological mediator between penile erection and the brain. NO synthase is a highly concentrated structure that is directly or indirectly involved in sexual behavior.
Some final words
Sexual behavior is nothing but an innate social behavior regulated by hormones. The neural circuits mediating sexual behavior and motivation in males and females are overlapping yet distinct. 
Even though the fundamental process that underlies sexual arousal may be similar, the intensity will vary from one individual to another. Hence, the different sexual behaviors.
Anyways, the central aim of learning about sexual behavior is to pursue a fulfilling and safe sex life to improve one’s sexual health.