Hormonal Control of Reproduction Flashcards
(35 cards)
What are the 2 groups of hormones?
- Water-soluble
- Fat-soluble
What are water-soluble hormones formed from?
Amino acids
Are water-soluble hormones hydrophilic or hydrophobic?
Hydrophilic
Why can’t water-soluble hormones pass through target cell membranes?
- 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
What does lipophilic mean?
Dissolve in fat
(Fat-soluble hormones are lipophilic)
What are fat-soluble hormones usually formed from?
Cholesterol
Also referred to as steroid hormones
What happens when fat-soluble hormones pass through membrane?
- 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
What are the 3 principal glands involved in male reproductive hormone production (hypothalamic-pituitary-gonadal axis)?
- Hypothalamus
- Pituitary gland
- Gonads (testes)
What are the 3 principal glands involved in male reproductive hormone production usually referred to?
Hypothalamic-pituitary-gonadal axis (HPG axis)
What type of effects can sex hormones have?
- Organising effects - occur mostly at sensitive
stages of development – e.g. might
determine whether brain & body will
develop m or f characteristics - Activating effects - occur at any time of life & activate a particular response
What are sex limited genes?
- 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
What are the 6 major hormones involved in male reproduction?
- Gonadotropin Releasing Hormone (GnRH)
- Follicle Stimulating Hormone (FSH)
- Luteinising hormone (LH)
- Androsterone
- Testosterone
- Sex Hormone-Binding Globulin (SHBG)
What is dihydrotestosterone (DHT)?
- A more potent form of testosterone
- Androsterone can be directly converted to it
What is testosterone synthesised from?
Cholesterol
Are SHBG (sex hormone-binding globulin) levels higher in males or females?
Females
Does testosterone increase or decrease as men age?
Decrease
What are 4 side effects of testosterone & anabolic steroid abuse?
- Testicular atrophy
- Infertility
- Prostate enlargement
- Liver damage
The cyclic changes that occur in the female oestrus/menstrual cycle are initiated & regulated by hormones from where?
- Hypothalamus
- Pituitary
- Ovaries
- The hypothalamic-pituitary-ovarian (HPO) axis
What is the results of an increase in oestrogen?
(3 points)
- 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)
What happens once oestrogen levels peak?
- 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
When does progesterone levels start to increase?
During pro-oestrus & peak during ovulation
Following ovulation, what does progesterone & oestrogen inhibit?
LH & FSH secretion
What does the corpus luteum secrete for pregnancy?
Progesterone
What does the body release if fertilisation doesn’t occur & why?
- Prostaglandins
- Causes corpus luteum to break down
