Brain And Behavior- Reproductive Behavior

During prenatal development, the internal reproductive structures of the male require the suppression of the Mullerian system by anti-Mullerian hormone (AMH) and the secretion of androgens. Anti-Mullerian hormone prevents the development of female reproductive structures, while androgens, such as testosterone, promote the development of male reproductive structures. Therefore, both A (suppression of the Mullerian system by AMH) and D (secretion of androgens) are correct in explaining the prenatal development of the internal reproductive structures of the male.

The gene Sry is responsible for dictating the conversion of undifferentiated gonads into testes. This gene plays a crucial role in determining the development of male sexual characteristics. It is located on the Y chromosome and is activated during embryonic development. The presence of the Sry gene triggers a cascade of events that lead to the development of testes and the production of male hormones. Without the Sry gene, the undifferentiated gonads would develop into ovaries instead.

Primary sex characteristics are the physical features that are directly involved in reproduction, such as the gonads (testes in males and ovaries in females). Enlarged breasts are an example of secondary sex characteristics, which are physical features that develop during puberty but are not directly involved in reproduction.

The difference between an organizational hormone effect and an activational hormone effect is that organizational effects are permanent. This means that once the organizational effects occur, they are long-lasting and cannot be reversed. On the other hand, activational effects are not permanent and can be temporary, as they are mediated by receptors and can be influenced by various factors. Therefore, the key distinction lies in the permanence of the effects.

The genetic sex of a fetus is determined by the father's sperm. Sperm carry either an X or Y chromosome, while eggs always carry an X chromosome. If a sperm carrying an X chromosome fertilizes the egg, the fetus will be female (XX). If a sperm carrying a Y chromosome fertilizes the egg, the fetus will be male (XY). Therefore, the father's sperm determines the genetic sex of the fetus.

Castration in male rats eliminates the production of testosterone, which is responsible for male sexual behaviors. However, when male rats are given injections of estradiol and progesterone, which are female sex hormones, they can exhibit female sexual behaviors. One such behavior is lordosis, which is the arched-back, receptive posture displayed by female rats during mating. Therefore, it is expected that the male rat, in this case, would show lordosis in response to another male, as it has been feminized by the hormone injections.

Lordosis is a mating behavior in female rats where they arch their back and lift their hindquarters to facilitate copulation. This behavior is a clear example of receptivity, as it demonstrates the female rat's willingness and readiness to engage in sexual activity.

Androgen insensitivity syndrome is a disorder where individuals with XY chromosomes have impaired response to male sex hormones (androgens). This results in the development of female external genitals despite having testes. The testes are present but are not able to fully masculinize the external genitalia, leading to the appearance of female external genitalia. This condition is caused by mutations in the androgen receptor gene, which prevents the normal development of male sexual characteristics.

Menstruation is triggered by the reduced secretion of estradiol and progesterone from the corpus luteum. The corpus luteum is a temporary structure that forms in the ovary after ovulation and secretes hormones to prepare the uterus for pregnancy. If fertilization and implantation of a fertilized ovum do not occur, the corpus luteum degenerates, leading to a decrease in estradiol and progesterone levels. This decrease in hormone levels causes the lining of the uterus to shed, resulting in menstruation.

Androgen insensitivity syndrome (AIS) is a condition where individuals with XY chromosomes have a reduced ability to respond to male sex hormones. This leads to a range of physical characteristics that differ from typical males. Untreated AIS individuals typically have female external genitals, breast growth and development, and the inability to have children due to the absence of a uterus and fallopian tubes. However, they do not have female internal genitals, as AIS prevents the development of a uterus and fallopian tubes.