Lecture 14- Sex

Question 1

Sexual dimorphism:

Answer 1

the condition where two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs. (subtle or exaggerated, can include differences in size, weight, color, behavior) or secondary sex characteristics (puberty features)
-is associated with genetic and hormonal differences, both before and after birth.
-are reproductive behaviors: courting, mating, parenting, aggression

Question 2

Gametes:

Answer 2

-are mature reproductive cells made by gonads (ovaries or testes), they are either ova or sperm.
-gametes only have one copy of each chromosomes (mix of mother and father)
-one pair of chromosomes are called Sex chromosomes (x and Y varieties)

Question 3

Sex determination 5 factors:

Answer 3

1.Sex chromosomes: XX or YY
2.Gonads: testes or ovaries*
3.-Sex hormones: androgen signaling
4.Internal reproductive anatomy*
5.External anatomy*

*-> three categories of sex organs

Question 4

Mullerian system vs Wolffian

Answer 4

Mullerian system: Embryonic precursor of female internal sex organs

Wolffian system: Embryonic precursor of male internal sex organs
Second month of gestation: develop either ovaries or testes
Third month: mullerian or wolffian

Question 5

SRY gene:

Answer 5

located on the Y chromosome encodes a protein that causes undifferentiated fetal gonads to develop into testes.
(overpowers xx ovary instructions, xxy develop testes

Question 6

Male sex organ development:
Defeminizing,
Masculinizing,
Androgens

Answer 6

Defeminizing: effect of anti-mullerian hormone early in development which prevents development of female anatomy
Masculinizing effect: effect of androgen hormones early in development, which triggers development of male anatomy.
Androgens: male sex hormones (testosterone)

Question 7

Female sex organ development:

Answer 7

XX chromosome> development of ovaries > which are largely silent until puberty
-puberty triggered by hormone release from gonad

-absence of anti mullerian signaling= develops into internal females reproductive anatomy, inner vagina, uterus, fallopian tubes
-absence or testosterone signaling, external female sex organs develop while wolffian withers away

Question 8

Turner syndrom vs Swyer syndrom:

Answer 8

Turner syndrome: only have one sex chromosome (X0)

Swyer Syndrome: you are XY but have bad SRY gene

-both cases, gonads do not develop (ovaries or testes) but female sex organs develop normally.
-infertile, no natural puberty

Question 9

Androgen insensitivity syndrome:

Answer 9

results in anatomical defeminization with partial or no masculinization.
-no internal sex organs develop, infertile, short vagina
-external genitalia is fully masculinized
-ambiguous external genitalia

Question 10

-Behavioral defeminization,
-Behavioral masculinity,
-Activational effects:

Answer 10

-Behavioral defeminization: organizational effect of androgens on brain that prevent animals from displaying female-typical behaviors in adulthood,
-Behavioral masculinity: organizational effect of androgens on the brain that enables animals to engage in male-typical behaviors in adulthood.
-Activational effects: puberty causes sex hormones to be released by gonads, influencing the body and mind. (production of sperm, ovulation, horniness)

Question 11

Kisspeptin,
Gonadotropin releasing hormone
Gonadotropic hormones:

Answer 11

-Kisspeptin: neuropeptide produced by neurons in the hypothalamus that initiates puberty and maintains reproductive ability by triggering release of gonadotropin-releasing hormone.

-Gonadotropin releasing hormone: hypothalamic hormone that stimulates anterior pituitary gland to secrete gonadotropic hormones

-Gonadotropic hormones: hormones of pituitary gland (follicle stimulating hormone) that have stimulating effects on cells of gonads.

Question 12

Menstrual cycle: (humans)
vs Estrous Cycle: (like with cats)

Answer 12

Menstrual:
-female reproductive cycle
-characterized by menstruation, concealed ovulation
-sexual arousal is somewhat influenced by ovarian hormones, ability to mate is not

Estrous Cycle:
-Female reproductive cycle of most mammals
-females have estrous cycles, do not menstruate, they reabsorb their endometrium, and display a clear outward display of fertility.
-typically only sexually active during the estrous phase of their cycle

Question 13

Hormonal control of sexual behavior:

Answer 13

masculinize or feminize the brain of rodents by altering hormone signaling immediately after birth, after anatomical development of sex organs is complete.
Ex when male rodents are castrated at birth, they develop female-typical behaviors, will try to have sex with other males

Question 14

Congenital adrenal hyperplasia (CAH):

Answer 14

(if condition is present at birth) males excess androgen signaling from adrenal glands has minimal effect, but in females excess androgen signaling can cause some degree of masculinization of either body or brain.

Question 15

Female sexual behavior neural circuitry: VMH> PAG> nPGi> motor neurons in spinal cord

Explain VMH:

Answer 15

Ventromedial nucleus of hypothalamus (VMH): large nucleus in the hypothalamus that plays an essential role in female sexual behavior.
-electrical stimulations or vmh facilitates sexual behavior

Question 16

Male sexual behavior neural circuitry: mPOA> PAG> nPGi> motor neurons in spinal cord

Explain mPOA:

Answer 16

Medial preoptic area (mPOA): nucleus in the anterior hypothalamus that plays essential role in male sexual behavior
-electrical stimulation of mPOA in rodents elicits male copulatory behavior.
-within the mPOA, there is an area called the sexually dimorphic nucleus of the preoptic area.

Question 17

Pair bond formation:

Answer 17

Formation of long lasting, monogamous-ish pair bonds
-5% of mammalian species, sexually mature couples form long lasting monogamous pair bonds
-the formation of pair bonds seems to relate to two peptides in brain: vasopressin and oxytocin (elevated during sex, childbirth, breastfeeding)