Reproductive behavior and Sexual Orientation EXAM 3 Physio

Medical Preoptic Area (MPA)

The most critical area for male sexual behavior

Inhibits the PGi

The sexually dimorphic nucleus (SDN)

Inside the Medical Preoptic Area (MPA)

3-7 times larger than females ____

Order of male sexual behaviors

olfactory bulb→ vomeronasal bulb -→ amgydala → MPA → PGi of Medulla

PGi of Medulla

stops (rats) from getting an erections

To get an erection the PGi must be inhibited by the MPA

Ventromedial Nucleus of Hypothalamus (VPN)

The most critical area for a woman’s sexual behavior

increases lordosis when stimulated

Lordosis

positioning of the body that signals to the female’s counterpart that they are ready for sexual activity

Order of sexual behavior for females

olfactory → Medial Amygdala → Ventromedial Nucleus of Hypothalamus → periaqueductal Gray Matter → Reticular Formations

Periaqueductal Gray Matter

activated during orgasm

inhibits the Reticular Formation

Reticular Formation

Inhibits sexual readiness in women

Maternal Care (Rodents)

parturition

may cull the litter

helps offspring use the restroom through licking and potentially drinking the offspring’s urine for hydration

Some mice are better mothers (highlights motherhood being connected to genes)

parturition

Mother pulls offspring out with their teeth, eats the placenta, eats the umbilical cord, cleans the offspring, and feeds the offspring

Cull the litter

kill off some or all offspring until the children that were born become a more manageable size

Hormones that play a role in mothering behaviors

progesterone

prolactin

Progesterone

increases from insemination till birth

causes a burst of energy (cleaning energy/nesting)

helps maintain the uterine lining

Prolactin

Increases immediately after childbirth

responsible for milk production

plays a role in male refractory periods

not necessary for paternal behaviors

The MPA femal

brain structure for mothering

If removed → disrupts nesting and maternal care

receptor for estrogen, progesterone, and prolactin

Pre-natal Androgens

occurs during development and could affect an offspring’s sexual orientation or anatomy

What genital parts are equivalent to one another male v. female

labia → testicles

clit → penis

Androgen Insensitivity Syndrome (AIS)

Genetically male (XY)

A mutation occurs on the X chromosome

Lack of sensitivity to testosterone that would normally masculize the fetus

Anti-Mullerian to defeminize the person

External female genitalia, no uterus or fallopian tube

May be born with testes but gets removed due to cancer

Normal sex drive, orgasm, regular marriage, normally bigger boobs

Hermaphrodite

a person who has both a penis and a vagina, but only one is functional

Things affecting sexual orientation

The brain

Genetics

Birth Order

Cogenital Adrenal hyperplasia (CAH)

The brain in relation to sexual orientation

Levay was the first to discover their were size differences in the brain between gay men and staight men

Two brain structures related to homosexuality

Suprachiasmatic Nuclei of the Hypothalamus (larger is gay people)

Anterior Commissure (larger in gay people)

Genetics in relation to homosexuality

More than likely, multiple genes within the human body are acting as gay genes. There is not a single gene that can be pinpointed as the “gay gene.”

If one twin is gay, there is a percentage chance that the other twin is gay as well. These studies led to the belief that homosexuality may be tied to one or multiple genes

Birth Order in relation to sexual orientation

With each child born into a family it becomes more likely that the youngest child in the family will be homosexual

Congenital Adrenal Hyperplasia

caused by adrenal glands secreting abnormal amounts of testosterone during the prenatal period

Genetically, males this has no affect

women are born with an enlarged clitorous

may have a fused labia

can effect a persons sexual orientation