Zero to Hero (Module 2) Flashcards
LH secretion during follicular phase
Increases
LH secretion during pre-ovulation
Steady pulses and rising amplitude towards the last few days
LH secretion on the luteal phase
Decreased pulsatility and increased amplitude.
AFTER ovulation, oestrogen has a __________ feedback effect on FSH/LH
Negative
Prolactin inhibitory factors (PIF)
- Dopamine (DA)
- GABA
- GnRH-associated peptide (GAP)
Prolactin releasing factors
vasoactive intestinal polypeptide (VIP), thyrotrophin releasing hormone (TRH) and/or oestrogen
prolactin _________ its own release
inhibits
In the anterior pituitary gland, prolactin is secreted by
Lactotrophs
If we wanted to stimulate prolactin production, should we administer a dopamine agonist or antagonist?
Antagonist. Dopamine inhibits the production of prolactin, so administering an agonist would decrease prolactin release.
Hyperprolactinaemia – elevated serum prolactin in men would cause
- no pulsatile release LH
- decreased testosterone and libido
- erectile dysfunction
- infertility
Hyperprolactinaemia – elevated serum prolactin in women would cause
- no pulsatile release of LH
- amenorrhoea and decreased libido
- reduced response to GnRH
- no positive feedback
Normal age girls go through puberty
9-14 years old
Normal age boys go through puberty
11-14 years old
Changes in axillary and genital hair is mainly caused by
Androgens
Obesity has a different effect on females and males. What is this effect?
In females, obesity anticipates puberty due to the fat cells producing small amounts of oestrogen.
In males, obesity delays puberty.
Gonadostat Hypothesis
It is the theory that before puberty any signalling from gonadal steroids are immediately sensed and blocked (increased sensitivity). That is reduced in puberty, thus levels of gonadotrophins increase.
KISS neurons have a _________________ effect on GnRH neurons
positive/excitatory
Thelarche
Pubertal changes due to oestrogens.
Menopause normal age range
48-55 years old
Factors influencing menopause
Smoking cigarettes (comes earlier). Genetic factors Ethnicity Surgery (hysterectomy comes earlier) BMI (delays)
Peri-menopause
Phase before menopause can take years.
Hormones during peri-menopause
Lower oestrogen produced by follicles, lower testosterone produced by CL, more FSH and LH being released because of less negative feedback.
Detecting a woman is in peri-menopause through hormone levels
FSH> 40 u/l
LH> 30-40 u/l
Short term symptoms of menopause
Vasomotor and urogenital symptoms. Depression. Loss of sleep. Loss of libido. Memory loss and fatigue.
Medium/long term symptoms of menopause
Weight gain, osteoporosis, cardiovascular disease.
Proximate factors for breeding
Photoperiod, food, rainfall
Ultimate factors for breeding
Temperature, humidity, snowfall, rainfall, etc.
Short Day breeders
Breed when days are getting shorter (winter and autumn) usually to have the offspring by spring or summer. Example: sheep (5 months gestation)
Horses are ______ ______ breeders
Long day. Their gestation period is around 1 year so by mating in summer, they will have their offspring in summer.
Internal Body Clock is mainly regulated by
The suprachiasmatic nucleus (SCN)
Describe the pathway of photo optic input until the production of melatonin
Input -> SCN -> Superior Cervical Ganglion -> Pineal gland -> produces melatonin
What enzyme is the rate-limiting from melatonin production?
NAT (n-acetyl transferase)
Melatonin is produced during the day. True or false?
False, melatonin production is stimulated by the dark.
High levels of prolactin in males
Turn off GnRH and testosterone
Melatonin stimulates the release of
GnRH
Melatonin inhibits the release of
Prolactin
What hypothalamic hormone regulates LH secretion?
GnRH
- What happens to LH secretion in animals where
a. GnRH secretion is suppressed
b. GnRH concentrations are held high by giving a constant infusion.
In both cases, no LH secretion will occur as a pulsatile secretion of GnRH is necessary for the secretion of LH.
How is Prolactin secretion regulated?
Prolactin natural state is turned off. Its own release works as an inhibiting factor, but dopamine, GABA and GAP (GnRH associated peptide) are also inhibitors of prolactin. They are secreted by TIDA neurons.
Outline the main reproductive roles of oxytocin.
- Stimulates luteolysis
- Stimulates uterine contractions during birth, by acting on smooth muscle of uterus (myometrium)
- stimulates seminiferous tubules and epididymis contraction in males
- stimulates milk ejection from breasts
- initiates nursing behaviour in mothers
Where is Oxytocin made and where is it released from?
Oxytocin is made by magnocellular neurons and released onto the posterior pituitary.
What happens to female animals when oestrogen levels are kept high for a few days (explain)?
High oestrogen levels for a few days will lead to ovulation, as a high oestrogen level happens during the follicular phase when follicles are developing, getting bigger, more cells producing oestrogen.
List the major roles of prolactin in reproductive function.
Prolactin develops the breasts and helps with lactation in women.
