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Introduction: Genitals and Gender: What Makes Us Male and Female?

PART I  The Endocrine System

Hormones Act in a Great Variety of Ways throughout the Body

RESEARCHERS AT WORK: Our current understanding of hormones developed in stages

Hormones are one of several types of chemical communication

Hormones can be classified by chemical structure

Hormones Act on a Wide Variety of Cellular Mechanisms

Hormones initiate actions by binding to receptor molecules

Hormones can have different effects on different target organs

BOX 8.1: Techniques of Behavioral Endocrinology

Each Endocrine Gland Secretes Specific Hormones

The posterior pituitary releases two hormones directly into the bloodstream

Posterior pituitary hormones can affect social behavior

Feedback control mechanisms regulate the secretion of hormones

Hypothalamic releasing hormones govern the anterior pituitary

Two anterior pituitary tropic hormones act on the gonads

The gonads produce steroid hormones, regulating reproduction

Hormonal and neural systems interact to produce integrated responses

PART II  Reproductive Behavior

Reproductive Behavior Can Be Divided into Four Stages

Copulation brings gametes together

Gonadal steroids activate sexual behavior

RESEARCHERS AT WORK: Individual differences in mating behavior

The Neural Circuitry of the Brain Regulates Reproductive Behavior

Estrogen and progesterone act on a lordosis circuit that spans from brain to muscle

Androgens act on a neural system for male reproductive behavior

Maternal behaviors are governed by several sex-related hormones

The Hallmark of Human Sexual Behavior Is Diversity

Hormones play only a permissive role in human sexual behavior

PART III  Sexual Differentiation and Orientation

Genetic and Hormonal Mechanisms Guide the Development of Masculine and Feminine Structures

Sex chromosomes direct sexual differentiation of the gonads

Gonadal hormones direct sexual differentiation of the body

Changes in sexual differentiation processes result in predictable changes in development

Dysfunctional androgen receptors can block masculinization of the body

Some people seem to change sex at puberty

SIGNS & SYMPTOMS: Defining an Athlete’s Sex

How should we define sex—by genes, gonads, genitals?

RESEARCHERS AT WORK: Gonadal hormones direct sexual differentiation of behavior and the brain

Early testicular secretions result in masculine behavior in adulthood

Several regions of the nervous system display prominent sexual dimorphism

Social influences also affect sexual differentiation of the nervous system

Do Fetal Hormones Masculinize Human Behaviors in Adulthood?

What determines a person’s sexual orientation?