Chapter 5 - Sex Hormones and Human Sexuality Flashcards
What are hormones?
chemical messengers that are released by endocrine organs and carried throughout the body via the circulatory system; provide cxs between the NS and the reproductive system
how are hormones released into the bloodstsream?
through endocrine organs such as the gonads; small amounts produce strong and lasting effects
how are hormones regulated?
by feedback signals from every organ effected, especially the brian
what are se3x hormones?
regulate sexual maturity and reproduction
three main sex hormones
androgens, estrogens, progestogens
(oxytocin and vasopressin can also be considered sex hormones)
what is the HPG axis?
Hypothalamic‐pituitary‐gonadal axis; communication system between areas of the brain (the hypothalamus and pituitary gland) and the gonads that affects the production and release of sex hormones
what does the brain use to regulate sex hormone production?
the HPG axis
what is the hypothalamic hormone?
GnRH (gonadotrophin releasing hormone)
what are the pituitary hormones?
FSH (follicle simulating hormone); LH (luteinizing hormone)
what are the gonadal hormones?
testosterone (from testes); estrogen/progesterone (from ovaries)
in males, testosterone operates in a ____ loop
negative feedback
male system (?)
LH binds to cells inside the testes and causes them to secrete testosterone
explain the negative feedback loop for testosterone
Hypothalamus directly monitors testosterone
levels; this influences gonadotropin‐releasing hormone (GnRH) levels (released by hypothalamus); GnRH levels influence LH production (from pituitary); LH influences Testosterone production
ex: Low T > hypothalamus increases GnRH >
pituitary increases LH > T rises
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explain the negative feedback loop for sperm production
inhibin secreted by testes regulates the negative feedback loop for FSH; operates in a different area of the hypothalamus than T production
ex. Low Inhibin ‐> Hypothalamus increases GnRH ‐> Pituitary increases FSH ‐> Testes manufacture sperm
what regulate the female menstrual cycle
the interaction of the different components of the HPG axis
4 phases of menstrual cycle
- Follicular phase
- Ovulation
- Luteal phase
- Menstruation
describe the follicular phase
pituitary secreting high levels of FSH, stimulates a follicle in the ovary to bring an egg to the final stage of maturity; follicle also secrets estrogen at this time (affecting the endometrium)
ex. Low Estrogen/Inhibin ‐> Hypothalamus increases GnRH ‐> Pituitary increases FSH ‐> follicle/egg matures
-negative feedback loop
describe ovulation phase
Estrogen + Inhibin levels have risen to a high level, causing FSH levels to start to fall
– Consequently, the high estrogen levels stimulates the hypothalamus to produce GnRH, which stimulates the pituitary to produce LH
* So High E ‐> Increases GnRh ‐> Increasess LH
* This LH surge is what triggers ovulation
* Positive feedback loop; different area of hypothalamus
– The follicle ruptures open and releases a mature egg
describe the luteal phase
After releasing an egg, LH levels cause the follicle
in the ovary to turn into a glandular mass of cells
called the corpus luteum
* Corpus luteum secretes progesterone
– The progesterone from corpus luteum stimulates glands of the endometrium (uterus) to start secreting a nourishing substance
-Corpus luteum will only produce progesterone for about 10‐12 days (if no pregnancy)
– If no pregnancy, the corpus luteum withers and
the uterine lining cannot be maintained due to the decline in progesterone
– Sharp decline in both Estrogen and Progesterone levels at end of luteal phase
describe menstruation phase
– Shedding of the inner lining (endometrium) of the uterus
– Discharged through cervix and vagina
– Triggered by the sharp decline of Estrogen and
Progesterone at end of luteal phase
– FSH levels are now starting to rise again
average length of menstrual cycle
20-26 days (about 28)
In a 28 day cycle:
* Day 1 to 4/5 = menstruation
* Day 5 to 13 = follicular phase
* Day 14 = ovulation
* Day 15 to 28 = luteal phase
what are some issues that typically arise with the menstrual cycle
Dysmenorrhea; Endometriosis; Amenorrhea; Premenstrual syndrome (PMS) and Premenstrual dysphoric disorder (PMDD)
the development of secondary sex characteristics is triggered by the activation of ____
the HPG axis during puberty
male secondary sex characteristics
incr muscle mass, facial hair, growth of testes, lowering of the voice
female secondary sex characteristics
widened hips and pelvis, breast growth, incr fat tissue in arms/thighs/hips/butt
role of hypothalamus
highly responsive to hormones; provides sex hormones and influences sexual acts and the individual’s perception of sexuality
prenatally, the brain is very sensitive to ____
androgens and estrogens
-may affect identity and sexual attraction
the sexual brain is connected to brain regions that play a role in ____
thinking, perceptions, self control; sexuality, attraction, desire, and a sense of sexual self cannot be uncoupled from life experience
how do hormones affect sexuality?
strong evidence that sex hormones may directly affect sexual attraction, desire, and performance; androgens and estrogens play a direct role in genital and subjective arousal
ex. administration of testosterone can increase genital sexual arousal in both women and men
the relationship between sex and sex hormones is ____
reciprocal; sexual activity incr testosterone in men and women; Intimate physical contact (even of a non‐sexual nature) can increase testosterone in women; sexual arousal decreases the stress hormone cortisol and increases estradiol in women
how does sexual activity and other life factors affect hormone levels?
viewing erotica appears to incr testosterone levels in men and estradiol levels in females; imagining sexual interactions (fantasies) incr T levels in women; there is a bidirectional relationship between T levels and relationship status in women
what hormones work together and play a role in sexual/other reproductive behaviours?
oxytocin and vasopressin
oxytocin is associated with ____
childbirth, lactation, maternal behaviour, bonding
vasopressin is associated with ____
multiple aspects of human social and sexual functions such as increased heart rate and fluid balances
how do smells (of sex hormones) lead to sexual behaviour?
smells can activate areas in our emotional brain (limbic system) outside of conscious awareness
what are pheromones
produced in the apocrine glands (armpit and pubic areas); synthesis is controlled by androgens in males and females
what are the four pheromones identified in humans?
Territorial, menstrual/fertile, sexual, and
maternal‐infant
what is major histocompatibility complex (HCM)?
compounds that are found in genital pheromones and may communicate genetic info to sexual partners
what is perimenopause
signals a decline in fertility for women; usually in late 40s
when is a woman considered menopausal
no menstrual period in 12 months or more
menopausal women may experience a decline in libido due to ____
declining estrogen and estradiol levels
what is the most common sexual dysfunction among women of all ages?
low desire; affects 34%-43% of women in Western countries
from young adulthood to menopause, what happens to testosterone levels?
levels of circulating testosterone decline gradually
what is andropause?
falling testosterone levels in males over 50
what happens during andropause?
low libido; decreased strength/energy/stamina; incr irritability; decr enjoyment of life
aging men may experience what along with andropause?
bone and muscle mass loss; incr body fat; breast development; changes in cognitive functions
low libido is typically caused by what in older men?
hypogonadism
-can cause erectile dysfunction
-can be treated with androgen therapy
