Genes Affect Sex Differences in Behavior

Men and women can seem like they’re from different planets sometimes. Hormones help drive those differences. A new study shows how genes pass on the message. Hormones are the body's signaling molecules. They affect many aspects of development and biology. Researchers have long known that the sex hormones, such as estrogen and testosterone, drive certain differences in behavior between men and women. How these hormones exert their effects on a molecular level, however, isn't well understood. A team of scientists used DNA microarrays to analyze gene expression across the mouse brain. They particularly focused on the hypothalamus, a region known to be involved with hormone sensing. The team reported finding 16 genes that were expressed differently between the brains of male and female mice. A closer look revealed that these sex differences in gene expression weren’t limited to the hypothalamus. They were also found in the amygdala, a region implicated in processing emotions. These results also suggest that other complex behaviors might be similarly constructed by gene networks. Of course, genes aren't the only things that drive how people behave. But this research shows that genes may play an important role in complex human behavior.

How long does a hormone active once it is released?

Hormones that circulate freely in the blood remain functional for less than one hour. Some hormones are functional for as little as two minutes. A hormone becomes inactivated when it diffuses out of the bloodstream and binds to receptors in target tissues or is absorbed and broken down by cells of the liver or kidneys. Enzymes in the plasma or interstitial fluids that break down hormones also cause them to become inactivated. Other hormones (e.g., renin) are activated by enzymes that cleave the active portion from a larger circulating precursor molecule.

What is mixed gland?

The pancreas is a mixed gland because it has both endocrine and exocrine functions. As an endocrine gland, it secretes hormones into the bloodstream. Only one percent of the weight of the pancreas serves as an endocrine gland. The remaining 99 percent of the gland has exocrine functions. The acinar cells (also called acini, from the Latin meaning “grapes” because their structure resembles clusters of grapes) are responsible for secreting digestive enzymes.The pancreatic islets (islet of Langerhans) are cluster cells that secrete hormones. There are between 200,000 and 2,000,000 pancreatic islets scattered throughout the adult pancreas.

How long does a hormone remain active after it is released?

Hormones that circulate freely in the blood remain functional for less than one hour. Some hormones are functional for as little as two minutes. A hormone becomes inactivated when it diffuses out of the bloodstream and binds to receptors in target tissues or is absorbed and broken down by cells of the liver or kidneys. Enzymes in the plasma or interstitial fluids that break down hormones also cause them to become inactivated. Other hormones (e.g., renin) are activated by enzymes that cleave the active portion from a larger circulating precursor molecule

What is the difference between a sexually transmitted disease and a sexually transmitted infection?

The term “sexually transmitted disease” (STD) has been used frequently to describe infections of the reproductive tract. The term “disease” typically implies that symptoms are present such that the individual would be aware that an infection was present. However, the term “sexually transmitted infection” (STI) is currently favored. Using the STI term implies that infection can be present without the symptoms of disease. Because many infections of the reproductive tract can be asymptomatic, the term STI is often more appropriate than STD.

Which is the predominant in Thyroid hormone?

Thyroxine, or T4, also called tetraiodothyronine, contains four atoms of iodine. Triiodothyronine, or T3, contains only three atoms of iodine. The more common hormone is T4, which accounts for nearly 90 percent of the secretions from the thyroid. The amount of T3 in the body is concentrated and very effective. Both hormones have similar functions. Enzymes in the liver can convert T4 to T3.

What are the major hormones and aging plays any role in it?

The major groups of hormones are amine hormones, peptide and protein hormones, and steroid hormones. Amine hormones are relatively small molecules that are structurally similar to amino acids. Epinephrine and norepinephrine, serotonin, dopamine, the thyroid hormones, and melatonin are examples of amine hormones. Peptide hormones and protein hormones are chains of amino acids. The peptide hormones have 3 to 49 amino acids, while the protein hormones are larger with chains of 50 to 200 or more amino acids. Examples of peptide hormones are antidiuretic hormone and oxytocin. The larger thyroid-stimulating hormone and follicle- stimulating hormone are examples of protein hormones. Steroid hormones are derived from cholesterol. Cortisol and the reproductive hormones (androgens in males and estrogens in females) are examples of steroid hormones. Most endocrine glands continue to function and secrete hormones throughout an individual’s lifetime. The most noticeable change in hormonal output is in the reproductive hormones. The ovaries decrease in size and no longer respond to FSH and LH, resulting in a decrease in the output of estrogens. Although the hormonal levels of other hormones may not change with aging and remain within normal limits, some endocrine tissues become less sensitive to stimulation. For example, elderly people may not produce as much insulin after a carbohydrate-rich meal is eaten. It has been suggested that the decrease in function of the immune system is a result of the reduced size of the thymus gland.