Sex: Evolutionary, Hormonal, and Neural Bases
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Questions and Answers

What behavior do female rats display to indicate they are receptive to mating?

  • Singing
  • Nesting
  • Ear-wiggling (correct)
  • Ejaculation

What is necessary for the brain to release hormones that support pregnancy in rats?

  • External fertilization
  • Quitting copulatory behavior
  • Single intromission
  • Multiple intromissions (correct)

What does the Coolidge effect describe?

  • Increased parental behavior after mating
  • Variations in postcopulatory behavior
  • The faster resumption of mating with a different partner (correct)
  • The quick resumption of mating with the same partner

What is a characteristic of the copulatory lock observed in some species?

<p>The male's penis temporarily swells (C)</p> Signup and view all the answers

Where does internal fertilization take place?

<p>Inside the female’s body (B)</p> Signup and view all the answers

What behavior might occur after copulation in various species?

<p>Nurturing or parental behaviors (A)</p> Signup and view all the answers

What behavior do male rats exhibit as part of their mating ritual?

<p>Building nests (A)</p> Signup and view all the answers

What was the primary belief of Dr. John Money regarding gender identity?

<p>It is primarily determined by social learning in childhood. (C)</p> Signup and view all the answers

What is required for the masculinization of external genitals?

<p>Conversion of testosterone to dihydrotestosterone (B)</p> Signup and view all the answers

What significant event affected Bruce Reimer's early life?

<p>His circumcision was botched, leading to a loss of his penis. (A)</p> Signup and view all the answers

What was one outcome of the Reimer case on the scientific community's perspective?

<p>It fostered skepticism about effective treatments for gender assignment in infants. (D)</p> Signup and view all the answers

What happens in the absence of 5-alpha reductase?

<p>Masculinization of external genitals does not occur (C)</p> Signup and view all the answers

Which of the following describes appetitive behaviors in reproductive behavior?

<p>Establishing, maintaining, or promoting sexual interaction (C)</p> Signup and view all the answers

What condition was discovered in Caster Semenya?

<p>5-alpha reductase deficiency. (D)</p> Signup and view all the answers

Which stage of reproductive behavior follows sexual attraction?

<p>Appetitive behavior (C)</p> Signup and view all the answers

What notable characteristic did Caster Semenya possess regarding her chromosomes?

<p>XY chromosomes. (D)</p> Signup and view all the answers

How did Brenda Reimer's experience reflect on her social treatment during childhood?

<p>She was often bullied and teased, which influenced her behavior. (B)</p> Signup and view all the answers

What factor aids in sexual attraction among species?

<p>Learned associations and physiological readiness (C)</p> Signup and view all the answers

Which of the following statements best encapsulates the complexity of sex and gender?

<p>Both biological and psychological influences play a role in gender identity. (A)</p> Signup and view all the answers

What action did David Reimer take at age 14 that marked a significant shift in his gender identity?

<p>Decided to live as a man. (C)</p> Signup and view all the answers

Which factor is crucial but not entirely determinative of gender identity, according to recent perspectives?

<p>Hormonal influences during early life. (D)</p> Signup and view all the answers

Why is there significant reluctance to study the biological aspects of sex and gender?

<p>Limited funding and interest in the topic. (C)</p> Signup and view all the answers

What role do pheromones primarily play in reproductive behavior?

<p>They guide reproductive behavior in many species. (B)</p> Signup and view all the answers

What is the effect of castration on a male rat?

<p>Decreases interest in mating behavior (B)</p> Signup and view all the answers

What is the significance of estrogen in female rats?

<p>It is necessary for the lordosis response (B)</p> Signup and view all the answers

How does the amount of testosterone influence the copulatory score in guinea pigs?

<p>There is a specific threshold of testosterone required (C)</p> Signup and view all the answers

What role does progesterone play in the reproductive behavior of female rats?

<p>It increases proceptive and receptive behavior (B)</p> Signup and view all the answers

What is the function of the ventromedial hypothalamus (VMH) in female rats?

<p>Regulates the lordosis response (D)</p> Signup and view all the answers

Which hormone is essential in making a female rat proceptive and receptive when ovaries are absent?

<p>A combination of estrogen and progesterone (C)</p> Signup and view all the answers

What happens to the dendritic trees of neurons in the VMH when estrogen levels increase?

<p>They increase in size (A)</p> Signup and view all the answers

How does the VMH communicate with other areas of the brain related to reproductive behavior?

<p>It utilizes a pathway through the periaqueductal gray to the medullary reticular formation (D)</p> Signup and view all the answers

What role does the medial preoptic area (mPOA) play in male rats?

<p>It coordinates male copulatory behavior. (D)</p> Signup and view all the answers

How does the paragigantocellular nucleus (PGN) influence male erection responses?

<p>It normally inhibits the erection response. (D)</p> Signup and view all the answers

Which structure detects pheromones that activate male arousal?

<p>Vomeronasal organ (VMO) (A)</p> Signup and view all the answers

What is a characteristic difference in sexual response between men and women?

<p>Men tend to have a refractory phase following orgasm. (D)</p> Signup and view all the answers

Which phase involves increased blood flow to the vagina and production of lubricating fluid?

<p>Excitement (C)</p> Signup and view all the answers

What is indicated by the interplay of hormonal stages, neural systems, and sensory information in reproduction?

<p>The complexity of reproductive behaviors. (C)</p> Signup and view all the answers

What defines the hormonal and pheromonal influence on sexual behavior?

<p>They are essential for determining sexual behavior. (C)</p> Signup and view all the answers

What distinct feature characterizes human sexual behavior compared to other species?

<p>High variability and subjective reactions. (A)</p> Signup and view all the answers

Which brain regions are activated in men when they view unseen cues related to cocaine or sexual images?

<p>Ventral striatum and amygdala (C)</p> Signup and view all the answers

What structure is responsible for the release of oxytocin during orgasm?

<p>Hypothalamus (D)</p> Signup and view all the answers

What unique finding was observed in women with spinal cord injuries regarding orgasm?

<p>They can still experience orgasms despite sensory information blockage. (C)</p> Signup and view all the answers

What is suggested about the difference in sex drives between males and females?

<p>Males have a stronger sex drive than females on average. (B)</p> Signup and view all the answers

What complicates the identification of differences in sexual behavior between sexes?

<p>Diverse cultural factors and socialization influences. (A)</p> Signup and view all the answers

What trend has been observed regarding the differences within sexes versus between sexes?

<p>Differences within sexes are larger than those between sexes. (D)</p> Signup and view all the answers

What potential factor influences women's selectivity in choosing potential romantic partners?

<p>Socialization and cultural influences. (D)</p> Signup and view all the answers

What method is commonly used to study brain activation during orgasm?

<p>Functional MRI (fMRI) (B)</p> Signup and view all the answers

Flashcards

Reproductive Behavior

Species-specific behaviors that occur during the mating process.

Proceptive Behavior

A female rat's behavior that indicates she's ready to mate.

Copulation

The act of inserting the male's penis into the female's vagina, resulting in the release of sperm-carrying semen into the female.

Refractory Phase

The period of time after copulation when a male is unable to mate again.

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Coolidge Effect

The phenomenon where a male shows renewed interest in mating when presented with a new female partner.

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Estrus

The state when a female is receptive to mating.

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Lordosis

A specific posture adopted by the female during copulation, allowing for the male's penis to enter.

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Ovulation

The process of egg release from the female's ovaries. In rats, this occurs every 4-5 days.

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Sex

The biological differences between males and females, including chromosomes, hormones, and anatomy.

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Gender

The socially constructed roles, behaviors, and identities associated with being male or female.

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David Reimer's Story

The story of David Reimer, an individual who was assigned female at birth but raised as a male after a botched circumcision. The case highlights the impact of early life hormones and challenges the belief that gender is solely determined by social learning.

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5-alpha Reductase Deficiency

A condition where a person's genetic sex (XY chromosomes) does not match their physical sex due to a deficiency in the enzyme 5-alpha reductase. Individuals with this condition may have undescended testes, a shallow vagina, and external genitalia that may appear ambiguous.

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Caster Semenya's Case

The case of Caster Semenya, an athlete who faced scrutiny and medical testing due to her naturally high testosterone levels. Her case sparked debate about how to define and classify gender in sports.

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Neurobiology of Sex

The study of how biological factors, particularly hormones, influence sexual behavior and attraction.

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Early Life Hormones

The idea that early life hormonal experiences play a significant role in shaping gender identity and sexual behavior.

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What Determines Gender?

It is a complex interplay of biology and environment. Gender identity is not solely determined by genetics, social learning, or hormones. It's a combination of all three.

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Pheromone

A chemical signal released by one animal that affects the behavior of another animal of the same species, often related to reproduction.

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5-alpha reductase & DHT

The conversion of testosterone into dihydrotestosterone (DHT) is essential for the development of external genitalia in males. This conversion is facilitated by the enzyme 5-alpha reductase.

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Sex & Gender Differences: 5-alpha reductase

The process of sexual differentiation, which involves the development of male or female characteristics, is influenced by the presence or absence of the enzyme 5-alpha reductase, which converts testosterone into DHT.

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Four Stages of Reproductive Behavior

This refers to the stages involved in sexual behavior, including the initial attraction, behaviors that induce or maintain interaction (appetitive), copulation (mating), and the postcopulatory behaviors that occur after mating.

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Sexual Attraction

The first stage of sexual behavior, involving the initial feeling of attraction to another individual.

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Appetitive Behavior

The behaviors that lead to and maintain sexual interaction. These behaviors might involve courtship rituals, partner selection, or other activities that promote mating.

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Postcopulatory Behavior

The behaviors that occur after mating, such as parental care, territory defense, or other post-mating behaviors crucial for reproduction.

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Pair Bond

A type of social bond where partners live together both before and after copulation.

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Sexual Monogamy

A type of sexual bonding where partners only mate with each other.

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Androgens

The hormones produced by the testicles that play a key role in male mating behaviors.

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Activational Effect (of hormones)

The process by which hormones activate specific behaviors. Think of a temporary effect.

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Organizational Effect (of hormones)

The process by which hormones influence the development of the organism's brain and body during early life. Think of a lasting effect.

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Ventromedial Hypothalamus (VMH)

A brain region critical for the female rat's lordosis response. Think of the brain's 'mating center.'

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Neural Circuitry of Mating

A chain of brain regions that control mating behavior. Think of a relay system.

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What is the mPOA?

A brain region involved in coordinating male copulatory behavior, particularly mounting.

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What does the PGN do?

A part of the brainstem that inhibits the erection response. The mPOA sends signals that counteract this inhibition, facilitating erection.

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What are pheromones?

Chemical signals that activate sexual arousal in males. They are detected by the vomeronasal organ (VMO).

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What is the medial amygdala's role?

This structures sends information about pheromones from the VMO to the mPOA, playing a role in initiating male arousal.

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What is lordosis?

The female rat's posture during mating, allowing for the male's entry. It's elicited by sexual signals from the male.

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What are the phases of human sexual response?

The four phases of human sexual response: excitement, plateau, orgasm, and resolution.

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What is the refractory phase?

A period of time after orgasm when a man cannot experience another orgasm. It's absent in women.

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What is the vomeronasal organ (VMO)?

The structure that allows the detection of pheromones.

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Unconscious Sexual Arousal

Brain regions like the ventral striatum, amygdala, and insula become active when individuals are exposed to unconscious cues related to cocaine or sexual images.

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Brain Regions Involved in Orgasm

The brain's response to sexual stimulation involves the activation of various structures, including the amygdala, cingulate cortex, nucleus accumbens, and hippocampus. This activation also triggers the release of oxytocin in hypothalamic areas after orgasm.

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Orgasm Without Sensory Feedback

Even with spinal cord injuries preventing sensory feedback from the pelvic region, women can still achieve orgasms. This suggests the vagal nerve plays a role in detecting stimulation and triggering brain activation similar to non-paralyzed women.

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Sex Differences in Behavior

While there are statistically significant differences between the sexes, they're often smaller than the differences within each sex. Determining if these differences are due to biology, socialization, or a combination is difficult.

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Women's Selectivity in Romance

Research suggests that women may be more selective in choosing romantic partners. While evolution is a possible factor, it's also crucial to consider other less biological explanations.

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Hormones and Sexual Behavior

Hormones play a critical role in regulating human sexual behavior and attraction. Understanding these hormonal influences is key to comprehending gender differences.

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Early Life Hormones and Gender

Early life exposure to hormones can significantly shape an individual's gender identity and sexual behavior. This highlights the complex interplay of biology and environment.

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Factors Contributing to Gender

Gender is not solely determined by genetics, social learning, or hormones. It's a complex interplay of all three factors, shaping an individual's self-identification and experience.

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Study Notes

Sex: Evolutionary, Hormonal, and Neural Bases

  • Gender determination is complex and not fully understood.

  • Biological and social factors both play a role.

  • 1965 twin case study (Brian and Bruce/Brenda) highlighted the complexity and controversies surrounding gender.

  • Dr. John Money, a proponent of gender identity being primarily determined by social learning in childhood, encouraged the family to treat Brenda as a girl.

  • Brenda, despite being raised as a girl, experienced significant psychological distress related to her gender identity. Later in life, she lived as "David Reimer", underwent gender reassignment surgery and committed suicide at age 38.

  • This case led to skepticism about infant genital reconstructive surgery.

  • Gender and sex also relate strongly to athletic competition.

  • The case of Caster Semenya demonstrated the complexity of sex and gender, along with legal challenges.

  • Semenya has issues with 5-alpha reductase, which affected her external genitalia, leading to her being raised as a girl, and her strong identification as a woman.

  • Without the 5-alpha reductase, she would not have been masculinized, and her sex assigned at birth would have been female.

  • Hormones and neural pathways, including the ventromedial hypothalamic area (VMH) in female rats and the medial preoptic area (mPOA) in male rats are crucial in regulating reproductive behavior.

  • Vomeronasal organ (VMO) detects pheromones, activating male arousal.

  • The Brain regions- including the nucleus accumbens, amygdala, and insula- are involved during human sexual arousal.

  • The amygdala, cingulate cortex, and the nucleus accumbens regions in the brain, along with the hypothalamic areas responsible for oxytocin release, are involved during orgasm.

  • Spinal cord injury does not affect a woman's ability to experience orgasm in some cases.

  • Research on sexual behavior and differences between sexes are fraught with potential confounds and limitations that need considering.

  • The differences between sexes are often smaller than differences seen within the same sex.

  • Hormones and pheromones play a key role in determining sexual behaviors, in humans and other species.

Sexual Behavior

  • Sexual behavior (especially in humans) exhibits high diversity.
  • Neural circuitry in the brain regulates reproductive behavior. Specific circuits are seen in rodents.
  • Pheromones may affect reproductive behaviors. Menstrual cycles of women living together may synchronize.

Reproductive Behaviors: Four Stages

  • Reproductive behavior can be divided into four stages:

    • Sexual attraction
    • Appetitive behavior
    • Copulation
    • Postcopulatory behavior

  • Sexual attraction brings males and females together, can be synchronized physiologically(e.g., odors reflecting estrogen levels).

  • Appetitive behaviors include pre-mating activities. Examples include ear wiggling, sniffing, singing, and nest-building in the rat.

  • Copulation involves intromission and ejaculation of sperm.

  • Post-copulation behavior varies by species. Some species have a refractory period, also the importance of hormones and/or pheromones.

Internal and External Fertilization

  • Internal fertilization takes place within the female body. Fusion results in a zygote.
  • External fertilization occurs outside the female body. (e.g., fish and frogs.)

The Hallmark of Human Sexual Behavior: Diversity

  • Human sexual behavior varies significantly from other species.
  • Humans report subjective sexual experiences, such as orgasm.
  • The four phases of response are excitement, plateau, orgasm and resolution.
  • Women often have more variety in their sexual responses.
  • Men, unlike women, experience a refractory phase following orgasm.
  • Orgasm in humans involves activity in various brain structures or regions.
  • Hormonal activity within the estrous/ovulatory cycle in female rats is important to reproductive behavior

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Lecture 17 - Sex and Behavior PDF

Description

Explore the complex interplay of biological and social factors in gender determination through significant case studies, including that of Brenda/David Reimer and Caster Semenya. This quiz delves into the implications of gender identity, societal perceptions, and athletic competition, highlighting the need for nuanced understanding in these debates.

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