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57 Cards in this Set

  • Front
  • Back
What region of the hypothalamus is th GnRH produced?
GnRH is produced in the preoptic nucleus.
What prevents downregulation of GnRh receptors in the anterior pituitary?
pulsitile release of GnRH
What are the hormones are the glycoproteins?
What is characteristic of glycoproteins
they are large and have an alpha and beta subunit. it is the beta subunit that provides specificity.
What does the large size do for the glycoproteins?
Gives them a long half life.
How does the composition the the glucoprotein hormones differ?
the alpha subunits are the same. It is the functional Beta subunits that differ among the hormones.
What is the target of LH and what doesit cause the target to do?
target of LH is the leydig cells of the testes and the leydig cells synthesize and secrete testosterone.
Where does the testosterone from the Leydig cells go.
circulation and Sertoli cells
what is the function of the sertoli cells?
Sertoli cells are the nerve cells that support spermatogenesis.
what do the sertoli cells require in order to support spermatogeneis and how does it get this requirement?
it required testosterone from the leydig cells. Injected testosterone will not produced a high enough concentration of testosterone in the sertoli cells to support spermatogenesis.
after reaching it's target tissue what converts testosterone and what is it converted to?
it is converted from testosterone to dihydrotestosterone by 5-alpha-reductase
what is the significance of dihydrotestosterone?
dihydrotestosterone is a more active form of testosterone.
what is testosterone converted ot dihydrotestosterone by?
What is the negative feedback for LH?
What is the normal negative feedback for FSH?
inhibin, which is released from the sertoli cells.
What is the target for FSH and what is the function of the target?
sertoli cells of the testes. their function is to support spermatogenesis.
What hormone do leydig cells have receptors for?
sertoli cells?
leydig = LH

sertoli = FSH
what do sertoli cells produce and secrete into the seminiferous tubules and what is the function of this?
The sertoli cells will produced and secrete into the seminiferous tubl=ules androgen binding protein which will bind local testosterone and create a very high concentration.
How much higher is the concentration of testosterone in the testes as compared to blood?
testosterone is 50 times higher in the testes
Is it possible to inject enough testosterone to support spermatogenesis?
What is required for the sertoli cells to maintain spermatogenesis?
Both testosterone from the leydig cells and FSH from the anterior pituitary.
What is a special type of activity that sertoli cells have
they have aromatase activity and thus it can convert testosterone to estrogen
What happens in the case of a sertoli cell tumor?
aromatase activity increases and circulating estrogen also increases.
What are other male tissues that have aromatase activity?
adipose tissue
what is the result of adipose tissue having aromatase activity
it means that obese males will have higher than normal levels of estrogen.
Why do women stop sharply decrease hormone secretion after menopause?
they run out of follicles in the ovaries which were responsible for producing the hormones.
What happens to males taking methyltestosterone injections?
The testosterone has a negative feedback on the LH from the anterior pituitary and thus the leydig cells do not get stimulated. With the decreased stimulation, the leydig cells atrophy and therefor there will no longer be a local production of testosterone. This causes a decrease in spermatogenesis.
What happens to the secretion of FSH in a person taking methyltestosterone injections?
at very high levels, testosterone will put give a negative feedback to FSH secretion, but it will bot be strong compared to the normal negative feedback from the sertoli cell inhibin.
What is being considered as a possible male controceptive?
How would inhibin work as a male contraceptive?
inhibin would inhibit FSH release. Both testosterone form the leydig cells and FSH from the ant. pit. are required for spermatogenesis. Thus the FSH requirement would be missing.
What happens with a constant GnRH infusion?
The receptors on the gonadotrophs in the anterior pituitary downregulate and thus they get less stimulation and secrete less LH and FSH, resulting in less sex hormones.
In a male when are testosterone levels higheset
both in the fetus and as a young adult.
what does the development of male and female structures depend upon?
depends solely upon fetal hormonal evnironment, not the genetic makup of the fetus
If there is no hormonal input to the fetus, what develops?
female internal and external structures, whether you are a genetic male or female.
What hormones does the development of male structures require?
hCG, LH, testosterone, dihydrotestosterone, and Mullerian inhibiting factor (MIH)
explain how hCG, LH, and testosterone are needed for development of male internal and external structures.
hCG and LH are needed for the development of internal male structures. Together hCG and LH stimulate the Leydig cells to secret testosterone. This testosterone differentiates the WOLFFIAN DUCTS into the internal male structures
for the development of external male structures, the testosterone is converted to dihydrotestosterone by 5-alpha-reductase and this dihydrotestosterone is responsible for the differentiation of external structures and the PROSTATE GLAND.
What happens to the Wolffian ducts if there is no testosterone?
they regress to nothing
What is responsible the the differentialte of male external structures and the prostate gland?
What happens if a male fetus has a dificiency in 5-alpha-reductase activity?
The fetus will not produce enough dihydrotestosterone and will not differentiate male external structures or a prostate gland. Therefore, with no hormonal in put female external strucutes will automatically be formed.
If someone has a 5-alpha-reductase activity deficiency, when will the person notice this.
He will think that he is a girl until he hits puberty when he starts the go through the internal male puberty changes.
What significant hormonal activity will take place after delivery.
Sertoli cells will release Mullerian inhibiting factor (MIH) which will inhibit to development of the Mullerian ducts.
In what fetus are the mullarian ducts present?
both male and female
If the Mullarian Ducts are not inhibited by MIH, what will they do?
Mullarian ducts automatically develop into female internal structures.
What hormone prevents female structures growing in males?
If an adult male has a uterus, why is this?
during development the individual did not secrete MIH
When a male is approaching puberty, what initiates the release of testosterone?
A rise in LH precedes and initiates the release of testosterone.
What happens to the LH secretion in an older male?
LH secretion increases because there is less negative feedback from the testosterone. This is because the leydig cells have simply slowed down their production of testosterone.
During puberty, androgens promote what anabolic sequence of secretion?
If T4 is normal, increased androgens drive increased growth hormone which drives increased IGF-1
Why is IGF-1 so important?
IGF-1 is the major stimulus for cell division of the cartilage-synthesizing cells located in the epiphyseal plates of long bones. Thus androgens stimulate the growth of long bones.
Why are androgens important at the end of puberty?
At the end of puberty androgens promate the mineralization of epiphysial plates of long bone, and thus terminate the individulas growth spurt.
If a normal young male going through puberty is given methyltestosterone to increase athletic performance, how will it effect his height?
Although androgens initiate the growth spurt, they also terminate the growth spurt, and thus if someone in puberty is given extra androgens, he will mineralize the epiphysial growth plates and he will stop growing the thus be shorter.
What is another substance, besides testosterone, that can cause plate closure?
At what temperature does spermatogenesis take place?
4 degrees celcius cooler than the abdominal cavily, thus the testes MUST descend in to the scrotum in order to perform spermatogenesis
Parasympathetics generally do not run to sympathetics in arterial tissue. What is the one exception?
The exception is the arterioles of the penis.
What causes an erection and what is this change due to.
Dialation of the arterioles in the penis and this dialation is due to parasympathetic input.
What neurotransmitter is released from the parasympathetics at the arterioles in the penis?
What neural systems are required for ejaculation?
sympathetic and motor neurons.