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ZOOL 461 > Endocrine control of reproduction > Flashcards

Endocrine control of reproduction Flashcards

1
Q

Gonadotropin-releasing hormone (GnRH) length

A

10 amino acids

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2
Q

What hormone is the key regulator of reproduction in vertebrates?

A

GnRH

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3
Q

True or false: GnRH is the exact same sequence in every species

A

False
- the primary sequence of 24 different GnRH molecular forms have been elucidated in different species

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4
Q

Where do similarities lie between the primary structure of GnRH between different species?

A

Similarity exists between sequences at N- and C- terminal regions
- Evolutionary conservation
- Important for specificity of hormone receptor

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5
Q

Where is GnRH synthesized?

A

In the neurosecretory neurons in the hypothalamus, reaches anterior pituitary via hypothalamic-hypophyseal portal system

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6
Q

How is GnRH released and what does it stimulate?

A

GnRH is released in a pulsatile manner to stimulate release and synthesis of LH and FSH from gonadotropes in the anterior pituitary
- In humans, its one pulse every 90 mins.

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7
Q

True or false: GnRH used to be called LHRH before

A

True, this was before they knew that GnRH stimulated FSH production/release as well

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8
Q

What 8 main conditions are GnRH analogs used to treat?

A
  1. Precocious and delayed puberty
  2. Hypogonadism
  3. Anovulation
  4. Amenorrhea
  5. The premenstrual syndrome
  6. Inadequate luteal function
  7. Endometriosis
  8. Hormone-dependent neoplasia
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9
Q

How do opiates effect the release of GnRH?

A

They inhibit the pulsatile release of GnRH

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10
Q

How does estrogen affect GnRH?

A

Estrogen stimulates Kiss peptin, and Kiss peptin stimulates GnRH

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11
Q

What are kiss peptins?

A
  • Kiss peptins are produced by secretory neurons in the hypothalamus
  • Kiss peptin neurons synapse with GnRH neurons
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12
Q

Androgens (stimulate/inhibit) hypothalamus to produce GnRH

A

Androgens inhibit hypothalamus to produce GnRH

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13
Q

Estrogen can increase __ secretion
What is this important for?

A

LH
- This is important to bring about the ovulatory surge of gonadotropins

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14
Q

The effect of estrogen is mediated by increased production of…

A

Kiss peptins

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15
Q

LH and FSH production are inhibited by a combination of…

A

Estrogen and progesterone

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16
Q

What are pregnancy pills based on?

A

Based on a combination of estrogen and progestogens that inhibit ovulation
- Pills add a higher level of progesterone (LH inhibitory hormone)

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17
Q

In males, an androgen surge inhibits…

A

The pulsatile release of GnRH and LH
- The effect of androgens are primarily inhibitory

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18
Q

Inhibin and activin are…

A

Gonadal peptides

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19
Q

Where are inhibin and activin produced?

A

Produced in both human female ovary and male testis

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20
Q

Inhibin and activin are (dependent/independent) on/of GnRH

A

Independent

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21
Q

Inhibin and activin superfamily

A

Transforming growth factor-β (TGF-β) superfamily

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22
Q

Inhibin function

A

Inhibits secretion of FSH without affecting LH

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23
Q

Activin function

A

Stimulates secretion of FSH independent of GnRH in addition to other actions, without affecting LH

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24
Q

Label diagram on slide 15

A
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25
Q

During each ovarian cycle after puberty, a number of ________ depart from the ________ and start rapid pattern of _________ growth and development

A

During each ovarian cycle after puberty, a number of primordial follicles depart from the resting pool and start rapid pattern of gonadotropin-dependent (FSH) growth and development

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26
Q

After the follicle grows into a Graafian follicle from the primordial stage, it must achieve… (2 things)

A

Ovulation or become atretic

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27
Q

Most follicles undergo…

A

Atresia (degeneration that includes loss of the oocyte)
- Only few reach the preovulatory Graafian follicle stage

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28
Q

Label diagram on slide 16

A
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29
Q

Describe the four steps of ovarian development from primary follicle to Graafian follicle

A
  1. Primary follicle to begin with
  2. Theca and granulosa cells become more numerous and small spaces appear in the follicle. This structure forms the secondary follicle.
  3. The spaces become filed with follicular fluid and enlarge to form a single large cavity the antrum.
  4. The follicle enlarges to approximately 20-25 mm in diameter containing an oocyte of ~120 µm in diameter and become preovulatory (Graafian) follicle
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30
Q

When does meiosis start in an organism?

A

During the organism’s embryonic stage

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31
Q

During the embryonic stage of a female embryo, what stage does the ovum remain in? It remains in this stage until when?

A

Prophase I, and remains arrested until lit reaches a Graafian follicle form -> called re-initation of meiosis and is started by an ovulatory surge of LH

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32
Q

After ovulation, the ovum remains in what stage? It remains in this stage until when?

A

Gets arrested at metaphase II, and meiosis restarts only if the egg is fertilized.

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33
Q

True or false: Meiosis of a follicle to form an ovum results in 2 daughter cells

A

False, one of the daughter cells becomes a polar body (small in size) and detaches

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34
Q

How long is the menstrual cycle?

A

25-30 days

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35
Q

The menstrual cycle is divided into two parts, the ___ phase and the ___ phase

A

Follicular phase and the luteal phase

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36
Q

Follicular phase length

A

12-16 days

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37
Q

Luteal phase length

A

10-16 days

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38
Q

What separates the follicular phase and the luteal phase?

A

Ovulation

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39
Q

What does the follicular phase involve?

A

The maturation of the oocyte and ovulation

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40
Q

The follicular phase is primarily…

A

Estrogenic

41
Q

The luteal phase is predominantly…

A

Progestogenic

42
Q

During the follicular phase, there is an increase in [this hormone] mainly, which stimulates [this hormone] to enhance the production of [this hormone]

A

During the follicular phase, there is an increase in estrogen mainly, which stimulates kiss peptin to enhance the production of GnRH

43
Q

During the end of the follicular phase, there is a slight increase in [this hormone] which causes a dip in [this hormone]

A

During the end of the follicular phase, there is a slight increase in inhibin which causes a dip in FSH

44
Q

There is a decline in [this hormone] after ovulation

A

There is a decline in estrogen after ovulation

45
Q

GnRH pulse frequency increases during the ____ phase, and low during the ____ phase

A

GnRH pulse frequency increases during the follicular phase, and low during the luteal phase

46
Q

The increase in estrogen during the follicular phase stimulates an increase in the secretion of [this hormone] which….

A

The increase in estrogen during the follicular phase stimulates an increase in the secretion of LH which stimulates ovulation

47
Q

The corpus luteum secretes which hormone during the luteal phase?

A

Progesterone

48
Q

What effect does estrogen have on the endometrium?

A

It allows for hyperplasia and hypertrophy of endometrial cells
- Endometrium becomes thick and vascularized

49
Q

What do endometrial cells provide to the implanted embryo?

A

Nutrition

50
Q

Progesterone prevents…

A

Contractile filaments in uterine smooth muscle from contracting

51
Q

The decline in progesterone at the end of the luteal phase results in…

A

Spasms because contractions aren’t being prevented anymore
- Leads to menstruation because endometrial cells die

52
Q

What results in the ovulatory surge of LH/FSH?

A

Higher estradiol levels towards the end of the follicular phase stimulates kiss peptins which in turn stimulate GnRH, resulting in the ovulatory surge of LH/FSH

53
Q

Basal body temperature (increases/decreases) during ovulation

A

Increases

54
Q

At the beginning of the follicular phase, (FSH/LH) is higher than (FSH/LH)

A

At the beginning of the follicular phase, FSH is higher than LH

55
Q

The increase in FSH during the follicular phase (past LH levels) is initiated by [this hormone]

A

Activin

56
Q

Ovulation depends on which classes of molecules?

A

Prostaglandins and cytokines

57
Q

Surge of LH and FSH results in…

A

Meiotic maturation and ovulation

58
Q

After ovulation, granulosa and theca cells undergo _____ and form _____ cells called ______ which produce _____ and a larger amount of _____

A

After ovulation, granulosa and theca cells undergo luteinization and form luteal cells called Corpus Luteum which produce estrogen and a larger amount of progesterone

59
Q

The life span of a human corpus luteum is how many days? What happens after this time?

A

14 days
- After, it spontaneously regresses and results in a decline in progestogen and estrogen levels

60
Q

What happens to progesterone levels during pregnancy and how?

A

If pregnancy occurs, chorionic gonadotropin secretion from chorion of embryo prolongs progesterone secretion by sustaining the corpus luteum even as FSH and LH decline, and maintains the pregnancy

61
Q

The morning after pill is a progesterone _______, which functions to…

A

The morning after pill is a progesterone antagonist, which functions to contract endometrial cells. This aborts the embryo.

62
Q

Contraceptive vs. contragestive

A

Contraceptive: prevents conceptions of embryo
Contragestive: prevents implantation of embryo

63
Q

All steroid hormones are derived from ______ and differ only in the ______

A

All steroid hormones are derived from cholesterol and differ only in the ring structure and side chains attached to it.

64
Q

All steroid hormones are ____ soluble

A

lipid

65
Q

True or false: enzymes involved in steroid hormone synthesis have differential regulation based on follicular or luteal phase

A

True
- controls what steroids are produced during each phase

66
Q

What are the steps for steroid hormone synthesis? (6 steps)

A
  1. Cholesterol becomes pregnenolone (C21) through sidechain cleavage
  2. Pregnenolone (C21) becomes progesterone (C21) through activity of 3β- hydroxysteroid dehydrogenase (3β-HSD)
  3. Progesterone (C21) either becomes corticosterods (C21), or becomes 17α-hydroxyprogesterone (C21) through activity of 17α-hydroxylase
  4. 17αhydroxyprogesterone (C21) becomes androstenedione (C19) through activity of C17,20-lyase
  5. Androstenedione (C19) becomes testosterone (C19) or estrone (c18) through activity of aromatase
  6. Testosterone becomes estradiol (C18) through activity of Aromatase
67
Q

Cholesterol conversion to progesterone happens in the _____, while progestrone conversion into androgens/estrogens happens in the _______.

A

Cholesterol conversion to progesterone happens in the gonads and adrenal cortex, while progestrone conversion into androgens/estrogens happens in the gonads.

68
Q

True or false: there’s a much higher concentration of aromatase enzyme in males compared to females

A

False
- There’s a much higher concentration of aromatase in females compared to males

69
Q

Androgens have C__ strands, while estrogens have C__ strands

A

Androgens have C19 strands, while estrogens have C18 strands

70
Q

Progestogens and corticosteroids are C__ steroids

A

C21

71
Q

What are the 4 main effects of estrogens?

A
  1. Enlargement and maintenance of the vagina, uterus, uterine tubes, ovaries and external reproductive organs (primary sexual characteristics).
  2. Development of the breasts and the ductile system of the mammary glands.
  3. Increased deposition of adipose tissue in various subcutaneous layers, particularly in the breasts, thighs and buttocks (responsible for the formation of the female physique)
  4. Influence skin texture and vascularization, skeletal growth, hair distribution, electrolyte balance, feedback action on pituitary and brain, etc.
72
Q

True or false: breast tissue increases during the follicular phase

A

True
- Due to increase in estrogen

73
Q

True or false: during menopause, women get wrinkles, osteoporosis and low vascularization

A

True
- Due to decrease in estrogen

74
Q

What are the 4 main effects of progestogens?

A
  1. Promote secretory changes in the endometrium, preparing the uterus for implantation of the fertilized ovum
  2. Reduces uterine contraction and prevents expulsion of the implanted ovum
  3. Promotes secretion of nutrients by cells lining the fallopian tube
  4. Promotes development and secretion of alveolar tissue, and general swelling due to secretory development in breast tissue (develops structures that can nurse the young)
75
Q

What are the functions of the testis? (2 general functions, 4 points for 2nd reason)

A
  1. Provide spermatozoa
  2. Secrete hormones (both steroid and peptide hormones like activin) that:
    a) Promote development and maintain the male reproductive characteristics.
    b) Promote development and maintain the male secondary sexual characteristics.
    c) Regulate gonadotropin secretion and release.
    d) Exert influences on a number of nonreproductive components, including liver, kidneys, skin, skeletal muscle, bone, brain.
76
Q

Increased androgen production can (increase/decrease) natural opiate production

A

Increase

77
Q

In males, testosterone is a precursor to which molecule?

A

Dihydrotestosterone (DHT)

78
Q

True or false: DHT is only present in males

A

True

79
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on libido

A

Act on CNS to increase sexual activity (libido) -> Both males and females have increased libido due to testosterone

80
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on bone growth

A

Affects bone growth - fusion of epiphysis (both estrogens and androgens cause the apoptosis of cartilaginous cells in the epiphysis)

81
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on reproductive tract during adulthood

A

Maintains the reproductive tract during adulthood

82
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on voice

A

Lowers voice

83
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on behaviour

A

Affects CNS - aggressive behaviour

84
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on hair growth

A

Affects hair growth (beard, axillar, chest, pubic, etc.) and hair loss in forehead

85
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on gonadotropin secretion and release

A

Regulate gonadotropin secretion and release

86
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on anabolic effect and growth

A

Exerts anabolic effect and growth (male physique)

87
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on primary and secondary sexual characteristics

A

Control development of the primary and secondary male sexual characteristics

88
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on penis/scrotum

A

Penile and scrotal growth

89
Q

Effect of androgens (testosterone and dihydrotestosterone/DHT) on prostate, seminal vesicle, bulbouretheral gland, Sertoli cell maturation and androgen binding protein synthesis

A

Stimulate development of prostate, seminal vesicle, bulbouretheral gland, Sertoli cell maturation (critical for sperm production) and androgen binding protein synthesis

90
Q

What causes menopause?

A

As females age, the number of germ cells left in their ovary for fertilization decreases. Menopause is caused by a complete cessation of germ cells in the ovary (they run out).
- No follicles mean no estrogen/progesterone produced so there are many symptoms associated)

91
Q

What is andropause?

A

As males age, their testosterone secretion decreases (but they can still produce sperm)

92
Q

What are the common health effects of menopause? (6)

A
  1. Hot flashes
  2. Urinary problems (because vasculature is affected)
  3. Vaginal dryness (females become more prone to urinary infection)
  4. Mood changes, sleep disturbances, stress, depression (rare)
  5. Increase in heart disease and stroke
  6. Osteoporosis affects about 25% of menopausal women.
93
Q

Effect of androgens on spermatogenesis

A

Stimulates spermatogenesis

94
Q

There are much more (theca/granulosa) cells than (theca/granulosa) cells in the follicle

A

Granulosa, theca

95
Q

Granulosa cells secrete…

A

Testosterone
- Have large number of aromatase enzymes which convert the testosterone into estrogen

96
Q

Draw GnRH pulse frequency throughout follicular and luteal phases

A
97
Q

Draw the gonadotropic hormones (FSH and LH) throughout follicular and luteal phases

A
98
Q

Draw the ovarian hormone levels (inhibin, estrogen, progesterone) throughout the follicular and luteal phases

A

ZOOL 461 (11 decks)

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