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Mammalian Reproduction > Hormonal Control of Reproduction > Flashcards

Hormonal Control of Reproduction Flashcards

1
Q

What are the 2 groups of hormones?

A
  • Water-soluble
  • Fat-soluble
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2
Q

What are water-soluble hormones formed from?

A

Amino acids

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3
Q

Are water-soluble hormones hydrophilic or hydrophobic?

A

Hydrophilic

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4
Q

Why can’t water-soluble hormones pass through target cell membranes?

A
  • Cell membranes contain lipid components
  • Water-soluble hormone (e.g. FSH) bind to receptor molecules protruding from surface of target cell
  • Binding activates enzymes inside cell that regulates biochemical activity of the cell
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5
Q

What does lipophilic mean?

A

Dissolve in fat
(Fat-soluble hormones are lipophilic)

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6
Q

What are fat-soluble hormones usually formed from?

A

Cholesterol
Also referred to as steroid hormones

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7
Q

What happens when fat-soluble hormones pass through membrane?

A
  • Binds to a receptor to form a hormone-receptor complex
  • HRC moves to nucleus & binds to region of DNA
  • Binding causes genes to switch ‘on’ or ‘off’ the activity of enzymes that regulate activity of the cell
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8
Q

What are the 3 principal glands involved in male reproductive hormone production (hypothalamic-pituitary-gonadal axis)?

A
  • Hypothalamus
  • Pituitary gland
  • Gonads (testes)
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9
Q

What are the 3 principal glands involved in male reproductive hormone production usually referred to?

A

Hypothalamic-pituitary-gonadal axis (HPG axis)

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10
Q

What type of effects can sex hormones have?

A
  1. Organising effects - occur mostly at sensitive
    stages of development – e.g. might
    determine whether brain & body will
    develop m or f characteristics
  2. Activating effects - occur at any time of life & activate a particular response
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11
Q

What are sex limited genes?

A
  • Genes that control most of the differences between m & f
  • Present in both sexes but expressed in only 1 sex
  • Result = 2 sexes showing different phenotype but have same genotype
  • E.g. genes that control milk yield in diary cattle present in both bulls & cows, but only expressed in cow
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12
Q

What are the 6 major hormones involved in male reproduction?

A
  • Gonadotropin Releasing Hormone (GnRH)
  • Follicle Stimulating Hormone (FSH)
  • Luteinising hormone (LH)
  • Androsterone
  • Testosterone
  • Sex Hormone-Binding Globulin (SHBG)
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13
Q

What is dihydrotestosterone (DHT)?

A
  • A more potent form of testosterone
  • Androsterone can be directly converted to it
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14
Q

What is testosterone synthesised from?

A

Cholesterol

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15
Q

Are SHBG (sex hormone-binding globulin) levels higher in males or females?

A

Females

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16
Q

Does testosterone increase or decrease as men age?

A

Decrease

17
Q

What are 4 side effects of testosterone & anabolic steroid abuse?

A
  • Testicular atrophy
  • Infertility
  • Prostate enlargement
  • Liver damage
18
Q

The cyclic changes that occur in the female oestrus/menstrual cycle are initiated & regulated by hormones from where?

A
  • Hypothalamus
  • Pituitary
  • Ovaries
  • The hypothalamic-pituitary-ovarian (HPO) axis
19
Q

What is the results of an increase in oestrogen?
(3 points)

A
  • Initiates morphological changes in uterus & vagina
  • Triggers oestrous behaviour
  • Suppresses the release of GnRH (LHRH) by the hypothalamus & inhibits pituitary
    secretion of LH and FSH (negative
    feedback)
20
Q

What happens once oestrogen levels peak?

A
  • Inhibition of LHRH & gonadotrophin secretion ceases
  • Results in surge in LHRH/GnRH & subsequent surge in LH
  • This triggers ovulation- the Graafian follicle ruptures & egg is released
21
Q

When does progesterone levels start to increase?

A

During pro-oestrus & peak during ovulation

22
Q

Following ovulation, what does progesterone & oestrogen inhibit?

A

LH & FSH secretion

23
Q

What does the corpus luteum secrete for pregnancy?

A

Progesterone

24
Q

What does the body release if fertilisation doesn’t occur & why?

A
  • Prostaglandins
  • Causes corpus luteum to break down
25
Q

What happens as progesterone levels begin to fall?

A

FSH levels begin to rise & cycle begins again

26
Q

What happens if fertilisation occurs?

A
  • Zygote moves from oviduct to uterus under control of oestrogen
  • Progesterone prepares uterus for pregnancy by:
    • Decreasing muscular activity of uterus
    • Thickening the uterus lining
    • Producing nutrients to feed zygote
27
Q

How does progesterone prepare the uterus for pregnancy?

A
  • Decreasing muscular activity of uterus
  • Thickening the uterus lining
  • Producing nutrients to feed zygote
28
Q

In mammals that have oestrus cycles, what happens to the endometrium if conception does not occur?

A

It is reabsorbed

29
Q

What does the combined oral contraceptive pill contain?

A
  • Synthetic oestrogen (Estrogen)
  • Synthetic progesterone (Progestogen)
30
Q

How does the combined pill work?

A
  • Inhibits FSH and LH production in pituitary to prevent follicular development & ovulation
  • Progesterone thins endometrium, making it difficult for a fertilised egg to implant
  • Thickens mucus in cervix, so it is
    harder for sperm to move up the tract to reach an egg
31
Q

What does the mini pill contain?

A

Progesterone only

32
Q

How does the mini pill work?

A
  • Takes every day with no break
  • Suppresses ovulation (but not consistently)
  • Thickens cervical mucus to stop sperm
    reaching an egg
  • Thins endometrium to
    prevent implantation
33
Q

What is the morning after pill?

A
  • E.g. Levonelle
  • Progesterone-only hormone pill
  • Delays release of an egg from an ovary,
    therefore preventing pregnancy
34
Q

What are the 2 types of IUD?

A
  • Non-hormonal ones that contain copper
  • Hormonal ones that slowly release a low dose of a synthetic hormone called levonorgestrel
35
Q

How do copper IUD’s work?

A
  • T-shaped piece of plastic wrapped in copper wire with a dabbling ‘tail’ of threads
  • Produces an inflammatory reaction that is toxic to sperm & eggs, preventing pregnancy

Mammalian Reproduction (16 decks)

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