Chapter 12 Flashcards & Key Terms

5α-reductase
An enzyme that converts testosterone into dihydrotestosterone (DHT).
activational effect
A temporary change in behavior resulting from the administration of a hormone to an adult animal.
allele
Any particular version of a gene.
altricial
Referring to animals that are born in an undeveloped state and depend on maternal care, as human infants do.
androgen insensitivity syndrome (AIS)
A syndrome caused by a mutation of the androgen receptor gene that renders tissues insensitive to androgenic hormones like testosterone. Affected XY individuals are phenotypic females, but they have internal testes and regressed internal genital structures.
anti-müllerian hormone (AMH)
Also called müllerian regression hormone. A protein hormone secreted by the fetal testis that inhibits müllerian duct development.
appetitive behavior
The second stage of mating behavior; helps establish or maintain sexual interaction.
aromatase
An enzyme that converts many androgens into estrogens.
aromatization hypothesis
The hypothesis that testicular androgens enter the brain and are converted there into estrogens to masculinize the developing nervous system of some rodents.
aromatization
The chemical reaction that converts testosterone to estradiol, and other androgens to other estrogens.
castration
Removal of the gonads, usually the testes.
cloacal exstrophy
A rare medical condition in which XY individuals are born completely lacking a penis.
congenital adrenal hyperplasia (CAH)
Any of several genetic mutations that can result in exposure of a female fetus to adrenal androgens, which results in a clitoris that is larger than normal at birth.
Coolidge effect
The propensity of an animal that has appeared sexually satiated with a present partner to resume sexual activity when provided with a novel partner.
copulation
Also called coitus. The sexual act.
copulatory lock
Reproductive behavior in which the male’s penis swells after ejaculation so that the male and female are forced to remain joined for 5–10 minutes; occurs in dogs and some rodents, but not in humans.
dihydrotestosterone (DHT)
The 5α-reduced metabolite of testosterone; a potent androgen that is principally responsible for the masculinization of the external genitalia in mammalian sexual differentiation.
double-blind test
A test of a drug or treatment in which neither the subjects nor the attending researchers know which subjects are receiving the drug (treatment) and which are receiving the placebo (control).
ejaculation
The forceful expulsion of semen from the penis.
estrus
The period during which female animals are sexually receptive.
external fertilization
The process by which eggs are fertilized outside of the female’s body, as in many fishes and amphibians.
α-fetoprotein
A protein found in the plasma of fetuses. In rodents, α-fetoprotein binds estrogens and prevents them from entering the brain.
gamete
A sex cell (sperm or ovum) that contains only unpaired chromosomes and therefore has only half of the usual number of chromosomes.
guevedoces
Literally “eggs at 12” (in Spanish). A nickname for individuals who are raised as girls but at puberty change appearance and begin behaving as boys.
hermaphrodite
An individual possessing the reproductive organs of both sexes, either simultaneously or at different points in time.
indifferent gonads
The undifferentiated gonads of the early mammalian fetus, which will eventually develop into either testes or ovaries.
internal fertilization
The process by which sperm fertilize eggs inside of the female’s body, as in all mammals, birds, and reptiles.
intersex
Referring to an individual with atypical genital development and sexual differentiation that generally resembles a form intermediate between typical male and typical female genitals.
intromission
Insertion of the erect penis into the vagina during copulation.
lordosis
A female receptive posture in quadrupeds in which the hindquarter is raised and the tail is turned to one side, facilitating intromission by the male.
major histocompatibility complex (MHC)
A large family of genes that identify an individual’s tissues (to aid in immune responses against foreign proteins).
medial amygdala
A portion of the amygdala that receives olfactory and pheromonal information.
medial preoptic area (mPOA)
A region of the anterior hypothalamus implicated in the control of many behaviors, including thermoregulation, sexual behavior, and gonadotropin secretion.
medullary reticular formation
The hindmost portion of the brainstem reticular formation, implicated in motor control and copulatory behavior.
müllerian duct
A duct system in the embryo that will develop into female reproductive structures (fallopian tubes, uterus, and upper vagina) if testes are not present.
musth
An annual period of heightened aggressiveness and sexual activity in male elephants.
neonatal
Referring to newborns.
Onuf’s nucleus
The human homolog of the spinal nucleus of the bulbocavernosus (SNB) in rats.
organizational effect
A permanent alteration of the nervous system, and thus permanent change in behavior, resulting from the action of a steroid hormone on an animal early in its development.
orgasm
The climax of sexual experience, marked by extremely pleasurable sensations.
ovulation
The production and release of an egg (ovum).
ovulatory cycle
The periodic occurrence of ovulation.
ovum
An egg, the female gamete.
pair bond
A durable and exclusive relationship between a male and a female.
parabiotic
Referring to a surgical preparation that joins two animals to share a single blood supply.
paragigantocellular nucleus (PGN)
A region of the brainstem reticular formation implicated in sleep and modulation of spinal reflexes.
parental behavior
Behavior of adult animals with the goal of enhancing the well-being of their own offspring, often at some cost to the parents.
periaqueductal gray
The neuronal body–rich region of the midbrain surrounding the cerebral aqueduct that connects the third and fourth ventricles; involved in pain perception.
phallus
The clitoris or penis.
pheromone
A chemical signal that is released outside the body of an animal and affects other members of the same species.
postcopulatory behavior
The final stage in mating behavior. Species-specific postcopulatory behaviors include rolling (in the cat) and grooming (in the rat).
precocial
Referring to animals that are born in a relatively developed state and that are able to survive without maternal care.
proceptive
Referring to a state in which an animal advertises its readiness to mate through species-typical behaviors, such as ear wiggling in the female rat.
refractory phase
A period following copulation during which an individual cannot recommence copulation.
reticulospinal tract
A tract of axons arising from the brainstem reticular formation and descending to the spinal cord to modulate movement.
semen
A mixture of fluid, including sperm, that is released during ejaculation.
sensitive period
The period during development in which an organism can be permanently altered by a particular experience or treatment.
sex determination
The process by which the decision is made for a fetus to develop as a male or a female.
sexual attraction
The first step in the mating behavior of many animals, in which animals emit stimuli that attract members of the opposite sex.
sexual differentiation
The process by which individuals develop either malelike or femalelike bodies and behavior.
sexual dimorphism
The condition in which males and females show pronounced sex differences in appearance.
sexually dimorphic nucleus of the preoptic area (SDN-POA)
A region of the preoptic area that is five to six times larger in volume in male rats than in females.
sexually receptive
Referring to the state in which an individual (in mammals, typically the female) is willing to copulate.
sperm
The gamete produced by males for fertilization of eggs (ova).
spinal nucleus of the bulbocavernosus (SNB)
A group of motoneurons in the spinal cord of rats that innervate striated muscles controlling the penis.
SRY gene
A gene on the Y chromosome that directs the developing gonads to become testes. The name SRY stands for sex-determining region on the Y chromosome.
syrinx
The vocal organ in birds.
Turner’s syndrome
A condition seen in individuals carrying a single X chromosome but no other sex chromosome.
ventromedial hypothalamus (VMH)
A hypothalamic region involved in eating and sexual behaviors.
vomeronasal organ (VNO)
A collection of specialized receptor cells, near to but separate from the olfactory epithelium, that detect pheromones and send electrical signals to the accessory olfactory bulb in the brain.
wolffian duct
A duct system in the embryo that will develop into male structures (the epididymis, vas deferens, and seminal vesicles) if testes are present in the embryo.
zygote
The fertilized egg.
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