25

Red blood cells are not equipped with a motor system to propel them through the blood stream. Instead, they are passively transported through the vasculature by the the pumping action of the heart. The effects of dangerous situations on the skin have to do with hormonal effects on the blood vasculature, and not with direct effects on red blood cells. ...


23

Women have erections too! These erections are called clitoral erection. Clitoral erections are usually accompanied with vaginal lubrification. Just like men (see here), the absence of norepinephrine during the REM phase of the sleep causes erections. In women, this phenomenon is called Nocturnal clitoral tumescence while it is called Nocturnal penile ...


21

Yes. Menopause is common for long-lived mammals. For instance, in the wild, killer whales go in a sort of menopause as reported in 2009 by Ward et al. Front Zool. 2009 Feb 3;6:4. So it is not due to captivity. According to a Nature review, reproductive cessation has also been documented in non-human primates, rodents, whales, dogs, rabbits, elephants and ...


17

A hormone is defined as "a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism" (I'm just taking Wikipedia definition). Hormones work by binding to specific receptors present on their target cells so, if there is something in the environment that mimics the hormone, by ...


14

Yes, they do. The ovaries produce both testosterone and estrogen. Relatively small quantities of testosterone are released into your bloodstream by the ovaries and adrenal glands. Sex hormones are involved in the growth, maintenance, and repair of reproductive tissues [1]. The serum testosterone level in women with no acne, hirsutism, or menstrual ...


12

I'll point you to this article by A. Tuiten et al. To quickly answer your question, yes, testosterone does have an enhancing effect on the sexual behaviour of human healthy adult females. The (admittedly small) study indicated that after an dose of testosterone was given to the women there was found: a statistically significantly [sic] increase in ...


12

Short answer People with androgen insensitivity syndrome do not have a functional uterus and cannot bear a child. Background Androgen-insensitive genetic males may develop female genitalia and internal female reproductive organs. However, in both partial androgen insensitivity syndrome (PAIS) and complete androgen insensitivity syndrome (CAIS) the uterus is ...


11

As said by @dblyons, there has not been a lot of research (biochemical) on chameleons. So, the exact part of mechanism that you're looking for is still not understood. However, we have recently caught the broad end of the stick. Chameleons don't have special cells for color, their complete skin has a layer of pigments (dermal iridophores) which helps them in ...


11

Isn't it illogical to give more of insulin for a deficit amount of receptors? Seems like there is some confusion in the definition of type-2 DM itself. According to the American Diabetes Association: If you have type 2 diabetes your body does not use insulin properly. This is called insulin resistance. At first, your pancreas makes extra insulin to make ...


10

Some assumptions made in the question. There is an implicit assumption in your question which I don't think to be correct: you assume that any reaction of the human organism to stress (let's substitute "fright" by "stress" in your question) is a physiological reaction, meaning that this reaction somehow helps the organism to overcome the stressful situation....


10

Although male testes are responsible for huge testosterone secretion, testosterone can be produced by other organs both in males and females. So, women do have testosterone. Similarly, estrogen is also produced in men and not only in women. In addition, both sexes produce the androgen and the estrogen receptors, so endogeneous or external testosterone will ...


10

Short answer: yes. Although clearly the infradian changes in steroid hormones in females are quite "obvious", other changes are less evident, but happen nonetheless in males as well as in females. Most of the hormones produced by endocrine organs such as the hypothalamus (a region at the base of the brain) or the hypophisis are not secreted in a continuous ...


10

Short answer The increased fear responses during the night are believed to be mediated by elevated corticotropin-releasing hormone (CRH) levels in the brain that drive the fear responses in the amygdala. Background Fear responses can be experimentally assessed by recording the startle reflex. For example, loud noises can evoke gross startle responses in ...


9

Fetal testis produces testosterone from cholesterol. There is a peak of production around 15 weeks of gestation (the "masculinization programming window"). So the genotype of the fetus can affect testosterone levels directly via effects on the biosynthesis of the hormone, or indirectly by defective regulation of the pathway's activity. However, exposure to ...


9

There is a good open access review about the effects of different hormones on sexual arousal. In most instances, the hormone is acting on the brain, which signals the information to gonads and genitals via nerves (i.e., the hypothalamic-pituitary-gonadal axis). However, in a study in which I have participated, we found a more direct and probably ancient ...


9

This is true for the beginning of the disease. As a reaction to the reduced sensitivity of the cells in the body to insulin (and thus less uptake of glucose from the blood and a resulting hyperglycemia) the body produces more and more insulin to cope with this problem. At some point the insulin producing beta cells cannot increase the production anymore and ...


8

That book was likely crap, but in short the answer is yes, probably there is a genetic basis in the metabolism, with human 'types' that could benefit from a personalized nutrition. The discipline studying these relationship is called nutrigenomics, and the main concept is similar to what is being told for personalized medicine. The bad news is that ...


8

In short, because the easiest way to get the protein coding sequence of the gene is to create cDNA based on the mRNA, and insulin mRNA is only expressed in pancreatic cells. Insulin gene consists of two exons. That means, amplifying the genome will not give us a coding sequence -- two pieces of that sequence will be interrupted by a large, non-coding intron....


8

Yes, something can be both a hormone and an enzyme. There are a group of hormones known as peptide hormones. These are proteins (such as enzymes) that act as hormones indirectly (and maybe directly too?). A hormone is a chemical secreted by a cell that has some effect on another cell elsewhere in the body. In this case, the chemical just happens to be an ...


8

The quick answer is that only certain cell types express the required steroid hormone receptors that are necessary to induce signaling and gene regulation when bound to their target steroid hormones, like estrogen, testosterone, cortisol, etc. If no receptor is present, the steroid doesn't effect any change. The second part of the answer involves the ...


8

I found a nice article that has insights to this matter. As posted before me it is true that only adults, but not juvenile individuals show this difference. Direct and indirect effects of sex hormones on bone marrow erythropoiesis and renal erythropoietin production has been proven, but it works in both sexes the same way. Females are capable to elevate ...


7

Months to years - although the actual duration in a specific environment depends on the nature of that environment and is tied to oxygen level. Higher oxygen, faster degradation. Less oxygen, the estrogen molecules interconvert among various closely related molecules which hampers both their detection and their degradation. For more info, please see: ...


7

From what I have gathered, I would think that humans do have receptors that are able to detect pheromones. For example, some studies that have indicated human responses to pheromones. Of these pheromone responses, some have been traced to the olfactory mucosa and olfactory epithelium. The trace amine-associated receptors (TAAR) for which humans have 7 ...


7

This condition is also known as "lactic acidosis" and can be pretty dangerous, since it influences the pH of the blood. When we metabolize glucose to produce ATP and NADH it is metabolized finally to pyruvate in a process called glyolysis (I am not going into detail here since this is nicely explained in the Wikipedia). Pyruvate can then be used further in ...


7

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 ...


7

Short answer Oxytocin release has been associated with the cutaneous low-threshold (CT) afferent fibers in hairy skin. Background Oxytocin is released from the paraventricular nucleus in the brain in response to low intensity stimulation of the skin, such as touch, stroking and warm temperatures. In a recent review Uvnäs-Moberg et al. (2015) report that ...


7

Medical science has reached the point where it is able to consider performing uterine transplants in genetically female (cis-female) patients born without a uterus. In the MedlinePlus report, First Uterus Transplant Planned in U.S. doctors at The Cleveland Clinic have plans to perform the first uterus transplant in the US sometime in 2016. The article ...


6

I found this - Celec et al. (2003) Circatrigintan cycle of salivary testosterone in human male. Biological Rhythm Research 34: 305-315 Conclusion. We believe that this is the first study demonstrating the existence of circatrigintan and circavigintan rhythms of testosterone in human males. Our findings might have implications in human physiology and ...


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