Session 2 Flashcards
List the hormones involved in reproduction produced by the hypothalamus, anterior and posterior pituitary glands and gonads
Hypothalamus - GnRH, PRH, PIH (travel in hypophyseal portal circulation)
Anterior pituitary - FSH, LH
Posterior pituitary - oxytocin
Testes - testosterone, inhibin
Ovaries - oestrogen, progesterone, inhibin
List which cell type in the anterior pituitary gland produce which hormones
Gonadotrophs –> FSH, LH –> gonads
Thyrotrophs –> TSH –> thyroid
Corticotrophs –> ACTH, MSH –> adrenals, melanocytes
Somatotrophs –> GH –> liver, adipose tissue
Lactotrophs –> prolactin –> ovaries, mammary glands
Describe the control of gonadotropin secretion by the hypothalamus
Controlled via releasing hormones (GnRH) from neurones in median eminence.
Travel in hypophyseal portal circulation
GnRH is released under control of several different groups of nerve cells in a pulsatile release (1/hr)
GnRH release is under the influence of the brain (environment), body weight, circulating hormones
The amount of FSH secreted in response to GnRH is reduced by inhibin (granulosa cells in ovary, sertoli cells in testis)
Describe the action of gonadotropin on the testes and ovaries
Testes:
FSH –> Sertoli cells (within tubules)
LH –> Leydig cells (outside tubules)
Secretes testosterone, promotes spermatogenesis, increases inhibin (decreases FSH)
Circadian rhythm - increased in early morning
Environmental stimuli - light/dark, women
Ovary:
FSH –> granulosa cells –> enzymes to convert androgens to oestrogen
LH –> theca interna –> androgens (androstenedione)
Moderate/low oestrogen reduces GnRH secretion
High oestrogen promotes GnRH secretion (+ve feedback, LH surge)
FSH –> follicles grown –> increased oestrogen –> +ve feedback
Corpus luteum –> increased oxygen and progesterone –> progesterone prevents +ve feedback –> -ve feedback –> low FSH –> no new follicles
List the action of the gonadal steroids in the male and female
Determinative effects - qualitative, only partly reversible, mostly secondary sexual characteristics
Regulatory effects - highly reversible, rely on continual horn all stimulation for their maintenance
Male determinative - deepening of voice, increase in size and mass of muscles, bones, vocal cords, facial and body hair, increased stature, growth of le is
Male regulatory - maintenance of internal genitwlia (prostate, seminal vesicles, vas deferens, epididymis), metabolic (anabolic) action, behaviour e.g. aggression, sexual activity
Action of oestrogen - Fallopian tube function, thickening of endometrium, growth and motility of myometrium, thin alkaline cervical mucus, vaginal changes, calcium metabolism
Action of progesterone - thickening of endometrium into secretory form, thickening of myometrium but reduction of motility, thick acid cervical mucus, changes in mammary tissue, increased body temperature
Describe the changes occurring in the ovary during the ovarian cycle and describe the changes in the endometrium
- Preparation (follicular):
Follicles grow in ovary, uterus prepared for sperm transport and conceptus implantation, changes to facilitate sexual interactions - Ovulation:
Brief period of fertility (36h), formation of corpus luteum - Waiting (luteal):
Corpus luteum in ovary, changes in preparation for pregnancy
Ovary - growing phase –> ovulation –> corpus luteum –> corpus albicans
Endometrium - menses –> proliferative phase –> secretory phase
List the phases of the menstrual cycle
Beginning - follicles part developed, secreted very little steroid/no inhibin, low oestrogen/progesterone, high FSH
Mid-follicular - increased oestrogen, increased inhibin, decreased FSH, +ve feedback, increased LH
Ovulatory - LH surge
After ovulation - corpus luteum forms, increased progesterone/oestrogen, suppression of LH/FSH
Luteal phase - corpus luteum grows, increased progesterone/oestrogen, dies after 14 days, low oestrogen/progesterone
Describe the pattern of secretion of gonadotrophins and gonadal steroids over the normal menstrual cycle
Gonadotrophins:
Follicular phase - FSH binds to granulosa cells (promote development) –> secretes oestrogen and inhibin
LH binds to thecal cells (theca interna)
Pre-ovulation - LH surge stimulates ovulation
Luteal phase - LH maintains corpus luteum (increased oestrogen, v. increased progesterone)
Gonadal steroids:
Follicular phase - increased oestrogen
Luteal phase - increased progesterone
Describe the hypothalmic and pituitary mechanisms underlying cyclical gonadotrophins secretion and the interactions between the ovaries and the hypothalamus/pituitary
Pre-ovulatory:
GnRH –> FSH –> granulosa cells –> high oestrogen + inhibin
Inhibin selectively inhibits FSH, oestrogen +ve feedback, LH rises
GnRH –> LH –> theca interna –> androgens
Luteal stage:
GnRH –> LH –> corpus luteum –> high oestrogen and progesterone
Progesterone prevents high oestrogen, FSH inhibited, GnRH pulses fewer
List the actions of oestrogen and progesterone in the non-pregnant women
Oestrogen - fallopian tube function, thickening of endometrium, secretion of fluid, growth and motility of myometrium, thin alkaline cervical mucus
Progesterone - thickening of endometrium into secretory form, thickening but reduction of motility of myometrium, thick acid cervical mucus, preparation for pregnancy
Describe the effects of testosterone in the male
Deepening of voice, facial and body hair, increased stature, increasing size and mass of bones, muscle, vocal cords, growth of penis, aggression, sexual activity
Explain how testosterone release is regulated by feedback control
GnRH –> FSH –> Sertoli cells –> spermatogenesis, inhibin (inhibits FSH, increases LH)
GnRH –> LH –> Leydig cells –> testosterone –> decreased LH and GnRH (-ve feedback)
