neuroendocrine axis and feedback mechanisms Flashcards
hypothalamus pituitary target axes
the hypothalamic control of what gland underlies the ability of mammals to coordinate endocrine functions
pituitary gland
GnRH
- what 10-amino acid hypothalamic neuropeptide controls the function of the reproductive axis?
GnRH
GnRH
neurons of which nuclei of the hypothalamus release GnRH?
neurones of the arcuate and preoptic nuclei
GnRH
what does GnRH stimulate through the hypophyseal portal system and from what place
stimulates:
- LH
- FSH
from anterior pituitary
GnRH
how what type of secretion is GnRH secretion and what does this type of secretion govern?
- pulsatile
- governs release of pituitary gonadotrophins
GnRH
what are 3 factors that can influence GnRH secretion?
-stress
- exercise
- diet
GnRH
at what age is GnRH detectable in the hypothalamus and when is FSH and LH produced
- 10 weeks gestational age
- FSH and LH starts production between week 10-13
GnRH pulsatility
- what 5 upstream hormonal and neural pathways GnRH neurons are controlled
- morphological changes in GnRH neurones
- inhibitory and excitory afferent signals form distinct neurotransmitters
- the Kisspeptin-neurokinin b-dynorphin (kndy) neuronal network
- steroids negative feedback
- nutrition and metabolism
gonadotropins
Name the 2 main gonadotropins and what cells secrete them
- FSH and LH
- gonadotrophic cells under control of the HPG (HPO/HPT) axis
hypothalamic control
what does more rapid GnRH pulse frequencies favour?
favours LH secretion
hypothalamic control
what does slower GnRH pulse frequencies favour?
favours FSH secretion
peptide hormones
what are inhibins and where are they produced in males and in females
think FSHb subunit for first part
- circulating endocrine hormones originating in gonads that act on the pituitary to speficially inhibit expression of the FSHb subunit
Males:
- produced in sertoli cells in testes
females:
- produced in ovarian follicles
peptide hormones
what are activins and where are they produced
potent stimulatory effectors of FSH expression
- produced in the gonads and in the pituitary gland
peptide hormones
what is follistatin and what pule frequency increases the expresson of follistatin
- potential inhibitor of FSHb expression and secretion that works with inhibin.
- high frequency GnRH pulses
sex steroids
What 2 ways do Gonadal steroids control gonadotropins
- regulating GnRH expression
- regulating the production of gonadotropins directly