Sex: Evolutionary, hormonal, and neural bases

What are the four stages of reproductive behavior listed in the lecture?

sexual attraction, appetitive behaviors, copulation, and postcopulatory behaviors

What can contribute to sexual attraction?

psychological readiness to reproduce and learned associations, such as appearance

What is a pair bond, according to the notes?

an attraction in which a partner is chosen partly through the body’s response

What is appetitive behaviors

behaviors that establish, maintain, and promote sexual interactions

What are preceptive behaviors? Give examples from the notes

behaviors that help initiate interactions; examples listed include ear wiggling, a distinct walk, and approaching a male

What are receptive behaviors? give examples from the notes

behaviors indicating receptivity; examples include lordosis, moving the tail, and presenting hind

What male behaviors are listed as part of appetitive behavior

staying close to a partner, singing, and nest building

What is copulation

the mating stage during which sperm may be deposited and fertilization may occur

Where does internal fertilization take place?

inside the female’s body

What is a zygote?

a fertilized ovum formed by the fusion of sperm and ovum

what is the refractory phase

a period after copulation during which sexual behavior is reduced or cannot immediately resume; its length varies across species

What is the Coolidge effect?

a male may resume sexual behavior more quickly when presented with a new partner

What are postcopulatory behaviors?

behaviors that occur after copulation; they vary across species

What is a postcopulatory lock, according to the notes

a situation in which the head of the penis swells and the male cannot withdraw immediately

What is superfecundation

a situation in which offspring in the same litter can have more than on father

What is testosterones role in male rat sexual behavior

it promotes interest in females, faster and more frequent mounting, and ability to reach orgasm

What happens to a castrated male rats mating interest when testosterone is no longer produced

interest in mating decreases

What can testosterone injections do in castrated males?

They can reinstate sexual behavior; the notes state that low doses work better

How can testosterone affect sexual behavior through estradiol?

Testosterone can be converted into estradiol by aromatization; blocking aromatase inhibits male sexual response.

What is aromatization?

The conversion of testosterone into estrogen, including estradiol, by the enzyme aromatase

What role does oxytocin play in male sexual behavior?

It is involved in smooth-muscle contractions during ejaculation.

What role is prolactin implicated in?

The male refractory period.

Which hormones are important for female proceptive behavior?

Estrogens produced at the beginning of the ovulatory cycle.

Which hormones are involved in the female sexual behavior sequence described in the notes?

Estradiol and progesterone from the corpus luteum; estradiol is released first, followed about two days later by a progesterone surge

What does the arcuate nucleus of the hypothalamus secrete in the estrous-cycle sequence?

Gonadotropin-releasing hormone (written as gonadotropic RH in the notes)

What does the anterior pituitary secrete early in the estrous-cycle sequence?

Follicle-stimulating hormone (FSH).

What do ovarian follicles secrete in the estrous-cycle sequence?

Estradiol.

What does estradiol do to the uterine lining?

It causes the uterine lining to grow.

What does estradiol stimulate the hypothalamus to release, according to the notes?

LHRH (luteinizing-hormone-releasing hormone, also commonly called GnRH)

What does luteinizing hormone (LH) do in the estrous-cycle sequence

LH from the anterior pituitary triggers ovulation, when the follicle ruptures and releases the ovum.

What does the follicle become after ovulation?

The corpus luteum, which produces estradiol and progesterone.

What is the spinal nucleus of the bulbocavernosus (SNB)?

A sexually dimorphic spinal nucleus associated with motor neurons controlling a muscle attached to the base of the penis.

How does the SNB differ between male and female rats?

The SNB is larger in males than in females.

How does testosterone contribute to development of the SNB, according to the notes?

Testosterone binds androgen receptors and activates processes that produce trophic factors, which are taken up by motor neurons.

Where are bulbocavernosus motor neurons found in non-rodent mammals, according to the notes?

In Onuf's nucleus in the spinal cord.

What is the medial preoptic area (mPOA) associated with?

Mediating male sexual behavior.

What happens when the mPOA is electrically stimulated, according to the notes?

Male copulatory behavior is elicited.

What happens when the mPOA is lesioned, according to the notes?

Male sexual behavior is abolished, although motivation is not necessarily reduced.

What effect can castration have on male sexual activity, and what can testosterone do?

Castration decreases sexual activity; testosterone injections can reinstate it.

What happens to testosterone in the mPOA?

It can be aromatized into estrogen, which the notes associate with promoting neuron survival.

How does the mPOA connect sensory information with behavior?

It receives pheromone-related information and connects with motor systems, including the basal ganglia and SNB

What does the vomeronasal organ (VNO) detect?

Pheromones

How large is the sexually dimorphic nucleus of the mPOA in male rats compared with female rats?

The notes say it is about 3–7 times larger in male rats

What factor is listed as influencing the size of the sexually dimorphic nucleus of the mPOA?

The number of androgens the organism is exposed to during development.

What is the ventromedial nucleus of the hypothalamus (VMH) associated with?

Female sexual behavior.

What happens when the VMH is lesioned?

Lordosis is abolished.

What happens when the VMH is stimulated

Lordosis is facilitated.

Which hormones act in the VMH, according to the notes?

Progesterone and estradiol.

How does estrogen contribute to lordosis in the pathway described?

Estrogen activates the periaqueductal gray (PAG), which projects to the spinal cord and helps produce lordosis

What are pheromones?

Chemical signals that communicate information between animals and help coordinate reproductive activities

What structure detects pheromones?

The vomeronasal organ (VNO), which contains specialized receptor cells near but separate from the olfactory epithelium.

What pathway carries VNO information toward the mPOA?

VNO → accessory olfactory bulb → medial amygdala → mPOA.

What is the Bruce effect described in the notes?

Introducing urine from an unfamiliar intact male can cause spontaneous reabsorption of fetuses in a pregnant female rodent.

What is the Lee–Boot effect?

Crowded housing can slow and eventually stop estrous cycles in female rodents.

What is the Whitten effect?

Introducing urine from an intact male after female rodents' estrous cycles have stopped can restart estrus and synchronize the cycles.

What is an agonist?

What is an antagonist?

What is up-regulation

An increase in the number of postsynaptic receptors; associated with antagonists

What is down-regulation

A decrease in the number of postsynaptic receptors; associated with agonists

Why can receptor regulation matter when drugs are stopped?

The notes connect receptor changes with homeostasis, tolerance, and withdrawal; for example, extra receptors after antagonist exposure may no longer be blocked when the drug is stopped.

Which other topics does the handout flag for the exam?

Mechanisms of drug action, saltatory conduction, negative feedback, research into drugs' abuse potential, and possibly action potentials