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  #1  
Old 06-19-2012
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Default Memoirs of my Step 1 Day 1

Just started Physiology... Linda Costanzo .. ah man... Teach me thy art.. for thou have knowledge ... that i Yearn... + kaplan physiology notes....


EndoCrine Physiology :


Male Reproductive System : 6 15 pm ( Beijing Time )


1. Hormonal control of Testicular Function
GnRH


hypothalamic hormone
works via IP3 mechanism
acts on anterior pituitary gonadtrophs to increase FSH and LH secretion
If secreted pulastile proper actions occur
Continuous secretion first increases then permanently decreases LH and FSH secretion

LH

anterior pituitary hormone
works via cAMP/Protein kinase mechansim
acts on cell membrane of interstitial cells of Leydig -----> increase conversion of cholesterol to pregnenonlone -------- > increased levels of testosterone
Testosterone via paracrine mechanism helps in maturation of Sertoli cells---> receptors are located on nuclear chromatin of Sertoli cells ----> increase synthesis of proteins ------> increase nutrients from Sertoli cell to germ cell.
Clinical Pearl : In absence of LH or FSH, Spermatogenesis WILL NOT OCCUR. Both must be present for fertility.
Increased testosterone has a negative feedback effect on anterior pituitary and hypothalamus to regulate LH secretion.

FSH
Anterior pituitary hormone
works via cAMP/protein kinase mechanism
acts on the membrane of Sertoli cells to initiate spermatogenesis
Secretes inhibin B --------> Negative feedback to anterior pituitary ------> decreases FSH
Secrets ABP (androgen binding proteins ) which is a protein that helps to maintain high levels of testosterone in the developing germinal cells during spermatogenesis

Aromatase
Aromatization of the A-ring
Conversion of tesosterone to Estradiol
1/3rd in man arises from aromatization of Sertoli cells and remaining 2/3rds by aromatization in adipose tissue
Clinical Pearl : In Sertoli cell tumor in men , one sign may be extremely elevated estradiol level ( in men only )
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Old 06-19-2012
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Beijing Time ( 6 40 pm )

2. Age related changes in Testosterone secretion

I. Fetal life


The development of male and femal internal structures depends on hormonal interplay

No Hormonal input :
If no hormone is secreted at all
Wolffian ducts regress
Mullerian ducts develop

And the person will develop female internal and external structures ( no matter what the genotype )


Hormonal Input: The development of normal male depends on 3 hormones

LH ---->Testosterone
Tesotosterone ------>Dihydrotestosterone
Sertoli cells ------>Mullerian inhibiting Factor (MIF)

Absence of MIF :Male external structures + internal structures + uterus ( due to failure of mullerian ducts to regress)

Absence of testosterone : No male external structures or internal structures because in absence of testosterone Wolffian ducts regress ( epididymus, vas deferens, and seminal vesicles) and no dihydrotestosterone can be produced ( so no male external features either)

Absence of dihydrotestosterone : Female external structures because urogenital sinus and genital tubercle fail to differentiate into scrotum, penis, and prostate gland.


II. Childhood

After birth --------> testosterone and LH levels delcline and continue to remain low until puberty.

III. Puberty

Near puberty LH drivers increases , especially during sleep and also causes secretion of LH induced testosterone

IV. Adult

High levels paralleling each other persist

V. Senescence

Testosterone and inhibin secretions decrease with age. So LH increases. But this is less pronounced in men than women ( who undergo menopause)
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Old 06-19-2012
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Beijing Time 7 00 pm

3. Dependence of Spermatogenesis on Lower Temperatures

Spermatogenesis ceases at temp. of abdominal cavity
Failure of testes to descend before or shortly after birth leads to Cryptorchidism
If not surgically corrected ------> Permanent infertility

Cooling in scrotum provided by

4 degress lower temperature than abodominal cavity
Contractions and relaxations of the creamasteric muscle and scrotal skin rugae

Effect on FSH and LH in bilateral cryptorchidism

Increased FSH ----> due to decreased production of Sertoli cell inhibin
Increased LH ------> due to decreased production of testosterone by Leydig cells

4. Erection , Emission And Ejaculation

Erection ---> Caused by dilation of blood vessels ----> Parasympathetic response in the erectile tissue of penis ( corpora and ischio-cavernosus)
Increased blood flow into penis than outflow due to compression of penile veins

Emission----> Movement of semen from epididymus, vasa deferentia , seminal vesicles and prostate to ejaculatory ducts----> sympathetic response
Also sympathetic induced contraction of the internal sphincter - > prevents retrograde ejaculation ----> Prostatectomy one of retrograde ejaculation by destroying internal sphinter

Ejaculation ----> Rhythmic contraction of bulbospongiosus and ischiocavernosus muscles ----> Semen moves in direction of least resistance i.e urethera ---- > somatic motor nerves mediated NOT Paraysympathetic mediated
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Old 06-19-2012
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Beijing 8 26 pm

Done with female reproductive system .. Was really boringg.. bleggg...

Cant be bothered to type all that info here....

Any how .. a tiny break before I hit the Calcium Metabolism in Endocrine system...

Godspeed !
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Old 06-19-2012
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Are you taking your notes down on this forum? LOL!
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"The whole universe is in a continuous flux... What it will be like tomorrow neither I nor anyone else can say. Only tomorrow will bring the revelation".-Osho
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Old 06-19-2012
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Quote:
Originally Posted by drssbaz View Post
Are you taking your notes down on this forum? LOL!
Lol yeaa ... Actually I learn better when I write down my conceptss... And since my typing is faster than my writingg (strange as it may sounddd ) I decided to type ma notes and learn fasterrr
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Old 06-19-2012
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Quote:
Originally Posted by saltycoffee View Post
Lol yeaa ... Actually I learn better when I write down my conceptss... And since my typing is faster than my writingg (strange as it may sounddd ) I decided to type ma notes and learn fasterrr
Why not make a word file then? Coz after a certain number of posts this thread will be shut down by the administration. Then your memoirs will come in like a 100 editions by the time you finish prep.
Or are you planning on daily memoirs?
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Old 06-19-2012
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I agree

Quote:
Originally Posted by drssbaz View Post
Why not make a word file then? Coz after a certain number of posts this thread will be shut down by the administration. Then your memoirs will come in like a 100 editions by the time you finish prep.
Or are you planning on daily memoirs?
Yea I suppose I think I will make daily memoirs.. I cud save all my stuff in a word file but I guesss on the forum I feel like im in usmle environment... Helps with ma personal self discipline I guess *winks*....
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