control of reproduction in male Flashcards
when does puberty start?
several definitions:
age of first reproductive behaviour
age of first ejaculation
age at first spermatozoa in ejaculate
age at first spermatozoa in urine
age when threshold number of spermatozoa in ejaculate
what does puberty cause?
the resulting in the ability to accomplish fertilisation
sperm production will be continuous from then on
what is reproductive activity divided into?
physiological changes, hormonal
behavioural changes
what is responsible for the endocrine changes in the male?
hypothalamic-pituitary-gonadal axis
what hormone does the hypothalamus produce?
GnRH - gonadotropin-releasing hormone
what hormone does the pituitary gland produce?
FSH and LH
what hormone does the testicles produce?
testosterone
inhibin
activin
oxytocin
how does the season affect the endocrine changes in seasonal breeders, in females?
the pineal gland detects changes in daylight
produces melatonin during the dark hours
melatonin concentrations either inhibit or excite the HPG axis
there is still activity e.g. sperm production
if given enough encouragement, will mate out of breeding season
how can the season affect the efficiency of reproduction in male seasonal breeders?
depending on the season, it can alter the size of the testis which will change the amount of testosterone
in rams, August, September and October is the largest testis
September, October, and November produce the most amount of testosterone
how does GnRH do in the male?
the mechanism is the same as in the female
releases differently, in frequent, intermittent bursts
there is not a large surge
how does GnRH travel?
secreted by hypothalamus
goes via hypothalamo-hypophyseal portal system
acts on anterior pituitary
what does FSH do in the male?
initiates spermatogenesis
causes spermatogonia to become secondary spermatocytes
where does FSH travel?
secreted from the anterior pituitary gland
travels via the bloodstream
acts on the Sertoli cells in the testis
how is the FSH controlled?
GnRH = increase of FSH
inhibin increase = FSH decrease
activin increase = FSH increase
what does LH do the male?
it controls the testosterone secretion
cholesterol is a precursor
therefore, testosterone secretion is also pulsatile
pulsatile LH = Leydig cells unresponsive to continuous high LH
how does the LH travel?
from pituitary glands
through the bloodstream
acts on the Leydig cells
how are the LH pulse secretions?
occur far more frequently than in woman
what does testosterone do in the male?
drives sperm production
develops male genitalia
causes pubertal changes and accelerates growth and muscle development
accessory glands growth and function
controls libido and reproductive behaviour
how does testosterone travel?
secreted in Leydig cells
acts on the body parts
causes negative feedback loop to decrease LH
how is activin controlled?
decrease in the production of sperm causes the increase of activin
how is inhibin controlled?
increase in sperm production causes the increase of inhibin
where are activin and inhibin produced?
in the Sertoli cells
what does activin or inhibin cause?
increase in inhibin = negative feedback loop, decrease in FSH
increase in activin = positive feedback loop, increase in FSH
what does oxytocin effect?
acts on myometrium of the seminiferous tubules, rete testes and epipdidymis, causing contractions
where is oxytocin produced?
either leydig or sertoli cells
what causes behavioural changes?
testosterone drives male reproductive behaviour
what are the changes in behaviour?
increase libido
increase vocalisation
flehmen - entry of pheromones into vomeronasal organ
