Hypothalamic - Pituitary Gonadal Axis I Flashcards
What are the 7 things needed to reproduce?
βCorrect process of sex determination (genotypic sex) and differentiation (phenotypic sex)
βSexual maturation- Puberty
βProduction and storage of sufficient supply of gametes
βCorrect number of chromosomes in egg and sperm
βActual sexual intercourse
βFertilisation, implantation, embryonic and placental development
β nurture individual until capable of βindependentβ life
What is an example of positive feedback?
β Ovulation
Describe how the HPG axis works?
β+ve drive from the hypothalamus which activates the pituitary
β +ve drive causing hormonal release from the pituitary
β Causes release of steroid hormones from the gonads
β Work in a -ve feedback to regulate their production
What does type of hormones does the hypothalamus produce?
β Peptide hormones
What hormones does the hypothalamus produce?
βGonadotropin releasing hormone
βkisspeptin
What hormones does the pituitary produce?
β Follicle stimulating hormone
β LH
What hormones do the gonads produce?
β Estradiol β Progesterone β Testosterone β Inhibin β Activin
Describe the HPG axis in relation to FSH and LH?
β GnRH is released from the hypothalamus
β This binds to the receptor on the anterior pituitary
β LH and FSH are secreted
β FSH and LH are released into the circulation and bind to their receptors on the gonads
β this co-ordinates the secretion of estrogen, progesterone and androgens
Where is GnRH secreted into?
β Into the primary plexus of the median eminence
Where does GnRH travel after it is secreted?
β Into the hypophyseal portal into the anterior pituitary
What does GnRH act on?
β The gonadotroph cells in the anterior pituitary
What is the function of kisspeptin?
β Master controller of puberty
Where is kisspeptin expressed?
β In the arcuate nucleus
β AVPV nucleus
What do kisspeptin neurons do?
β They send signals upstream of GnRH to neurons
What receptor do the kisspeptin neurons bind to?
β GPR54 receptor on GnRH neurons
What can kisspeptin 54 cross?
β blood brain barrier
What type of hormone is kisspeptin?
β Peptide hormone that is cleaved from a large pre-pro structure
What is GnRH secreted in response to and where?
β Synthesized and secreted in response to kisspeptin
β From GnRH neurons
What type of release is GnRH?
β Pusatile
Where does GnRH bind?
β To the GnRH receptor on gonadotroph cells of the anterior pituitary
Where does GnRH travel from and to?
β from the arcuate nucleus to the median eminence to the anterior pituitary