MKT Library

Saturday is Sexy… Sunday is Movies Night

Our Brains and Sex (MKT Library Series – Part 1)

By Dr. Nibras Mohammed AlSumaidae | Neurosurgeon at Baghdad Medical City | Contributor – MKT Library

Part -1- Introduction

SEX. Ancient word of a great deep meaning, every living thing everywhere know about it, slight differences may occur among the various populations, but the core of it, remains similar.

Ancient civilizations considered the act of sexual intercourse a holy activity where they could associate their “gods” with it. However, sex is sex every time and everywhere.

With the power of science, which enlightens of our life, humans were/are able to understand it better. Science gives us the ability to describe the activity very well and allows us to uncover its dark mysteries.

We know how it is done, we know it’s a great way towards satisfaction & sexual pleasure within a relationship, and we are also aware that (among humans) sexual intercourse is not done for reproductive purposes only. Besides, science today allows people to reproduce without fully relaying on sex and sexual activities. In fact, modern science is continuously working on developing safe, more reliable and cheaper means of insemination (and perhaps asexually, someday). But, sex remains a requirement of a great importance.

We believe that knowledge is not something esoteric or exclusive to small group of people such as scientists, physicians or other members of these flocks. We believe that scientific knowledge should be available for the masses where we can educate them and teach them to learn and understand scientific evidence, proven facts rather than hidden mysteries and weird secrets (All wizards, run away!).

Sex is a complex, multisystem, multifactorial phenomenon that occurs across all living things. However, it seems to have its full meaning within mammals where the experience of a true intercourse, reaching the threshold (orgasm) with supercharged feeling & behaviors.

Nature gave us and other mammals the ability to attract, initiate, engage & accomplish this activity in a seemingly ascending manner. Nevertheless, human beings take sexual activity to a completely new level. Humans have the ability to develop new means and meanings of satisfaction, surpassing the natural role that seems to prevail among mammals.

We will be attempting to explore this issue in a fair yet (seemingly) easy to understand amount of details.

Sexual Arousal

Brain Activity

Images showing brain activation in response to F-M stimuli in the heterosexual group compared with the same regions in response to M-M stimuli in the homosexual group Image Source: http://www.ajnr.org/content/29/10/1890.figures-only

Our understanding of the process and initiation of sexual arousal is being enhanced by both animal and human studies, inclusive of basic science principles and research on clinical outcomes. Sexual arousal is dependent on neural (sensory and cognitive) factors, hormonal factors, genetic factors and, in the human case, the complex influences of culture and context. Sexual arousal activates the cognitive and physiologic processes that can eventually lead to sexual behavior. Sexual arousal comprises a particular subset of central nervous system arousal functions, which depend on primitive, fundamental arousal mechanisms that cause generalized brain activity, but are manifest in a socio-sexual context. The neurophysiology of sexual arousal is seen as a bidirectional system universal to all vertebrates.

The following review includes known neural and genomic mechanisms of a hormone-dependent circuit for simple sex behavior. New information about hormone effects on causal steps related to sex hormones’ nuclear receptor isoforms expressed by hypothalamic neurons continues to enrich our understanding of this neurophysiology.[1]

Sex

The cycle of sexual activity in men and women occurs in 4 phases–excitation, plateau, orgasm, resolution – which are guided by sexual desire. Male sexual activity is characterized by erection, seminal emission and ejaculation (orgasm), whereas female sexual activity is characterized by vaginal lubrication, erection of the clitoris and orgasm. These responses are under the control of numerous central and peripheral neural systems. The central supraspinal systems are mainly localized in the limbic system (olfactory nuclei, medial preoptic area, nucleus accumbens, amygdala, hippocampus etc.), in the hypothalamus and its nuclei (periventricular and ventromedial nuclei). Neural information travels through the brain stem, the medulla oblongata, the spinal cord and the autonomous nervous system to the genital apparatus. While we have very detailed knowledge of the neural mechanism, which controls the function of the male and female genital organs, in particular those mediating erection, very little is known of the central mechanism involved. Nevertheless, several neurotransmitters and neuropeptides, such as dopamine, glutamic acid, nitric oxide, oxytocin, ACTH-MSH peptides, are known to facilitate sexual function, while serotonin, gamma-aminobutyric acid (GABA) and opioid peptides reduce it.

At the level of the periventricular nucleus a group of oxytocinergic neurons projecting to extra-hypothalamic brain areas, including the spinal cord, have been identified, which facilitate erectile function and copulation when activated and reduce both when inhibited. Although the majority of results, which have clarified the mechanisms involved, have been performed in males, it is believed that similar mechanisms are also operative in females.[2]

Please await Part 2. We will go even deeper.


Reference

1-Schober JMPfaff D. The neurophysiology of sexual arousal, Best Pract Res Clin Endocrinol Metab. 2007 Sep;21(3):445-61.

2-Argiolas AMelis MR. The neurophysiology of the sexual cycle, J Endocrinol Invest. 2003;26(3 Suppl):20-2.


Dr. Nibras is an Iraqi, born in Baghdad in 1980. He completed high school in Baghdad gifted school (Al mutamyzeen). He was awarded his MB ChB from the University of Mustansyria, Department of Medical Sciences. Currently, he is a neurosurgeon in Baghdad Medical City. He will be awarded CAMBS from the Arabic Board of Neurosurgery. He likes writing poetry, prose and is very interested in electronics and developments of Medical Tools. He has more than 10 years of experience in this field. He joined MKT Library In late February of 2015.


Glossary:

Neurophysiology: the physiology of the nervous system.

Genomic: a discipline in genetics that applies recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyze the function and structure of genomes (the complete set of DNA within a single cell of an organism)

Isoforms: any of two or more functionally similar proteins that have a similar but not identical amino acid sequence and are either encoded by different genes or by RNA transcripts from the same gene which have had different exons removed.

Hypothalamic: a section of the brain responsible for hormone production. The hormones produced by this area of the brain govern body temperature, thirst, hunger, sleep, circadian rhythm, moods, sex drive, and the release of other hormones in the body.

Supraspinal: above the spine, and may refer to, above the spinal cord and vertebral column: brain.

Limbic system: a complex system of nerves and networks in the brain, involving several areas near the edge of the cortex concerned with instinct and mood. It controls the basic emotions (fear, pleasure, anger) and drives (hunger, sex, dominance, care of offspring).

Olfactory nuclei: a portion of the forebrain of vertebrates. It is involved inolfaction and has supposedly strong influence on other olfactory areas like the olfactory bulb and the piriform cortex.

Medial preoptic area: a region of the hypothalamus. According to the MeSH classification, it is considered part of the anterior hypothalamus. There are four nuclei in this region, according to Terminologia Anatomica (medial, median, lateral, and periventricular).

Nucleus accumbens: also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus.

Amygdala: a roughly almond-shaped mass of gray matter inside each cerebral hemisphere, involved with the experiencing of emotions

Hippocampus: the elongated ridges on the floor of each lateral ventricle of the brain, thought to be the center of emotion, memory, and the autonomic nervous system.

Periventricular: situated or occurring around a ventricle, especially a ventricle of the brain.

Ventromedial nuclei: VMN, also sometimes referred to as the ventromedial hypothalamus, VMH is a nucleus of the hypothalamus.

Medulla oblongata: the continuation of the spinal cord within the skull, forming the lowest part of the brainstem and containing control centers for the heart and lungs.

Gamma-aminobutyric acid (GABA): an amino acid that acts to inhibit the transmission of nerve impulses in the central nervous system

Opioid peptides: short sequences of amino acids that bind to opioidreceptors in the brain; opiates and opioids mimic the effect of thesepeptides. Opioid peptides may be produced by the body itself, for example endorphins.

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This entry was posted on March 8, 2015 by in Biology and tagged , , , , , , , , , , , , .

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