Physio 10

Question 0

gonadal sex for males

Answer 0

SRY gene encodes testis determining factor (TDF), a transcripion factor. When SRY is present, indifferent gonad becomes testes and germ cells develop into spermatogonia

Question 1

genotypic sex for males

Answer 1

Y chromosome = male

Question 2

Phenotypic sex for males

Answer 2

hormones produced by the gonads determine the phenotypic sex. Includes development of accessory sex organs, external genitalia that require the presence of dihydrotestosterone, and secondary sex characteristics

Question 3

XX male

Answer 3

in rare cases, the SRY gene translocates to the X chromosome. the ovum receiving the X chromosome with the SRY gene will develop into a male. crossing over between X and Y can leave an X chromatid with a substantial portion of the testis determining factor region and a Y without TDF.

Question 4

what do androgens made by the leydig cells promote?

Answer 4

differentiation of the wolffian duct, and prostate development

Question 5

primordial gonad

Answer 5

contains the germ cells. the genotype of the germ cells determines the fate of the gonad. considered indifferent before it differentiates into testis or ovaries.

Question 6

differentiation of the testes in males

Answer 6

mesonephros develops into the epididymis. wolffian duct develops into the vas deferens, seminal vesicles, and ejaculatory duct. mullerian ducts degenerate due to anti-mullerian hormone from sertoli cells

Question 7

differentiation of the external genitalia

Answer 7

in the absence of testosterone, the undifferentiated external genitalia develop into the female structures. testosterone, after conversion to dihydrotestosterone, stimulates the formation of male external genitalia. begins at 10 weeks of gestation

Question 8

hypothalamic-pituitary-gonadal axis function and stuff

Answer 8

regulates spermatogenesis and androgen production. GnRH stimulation and FSH and LH release are all pulsatile. constant levels of GnRH prevents LH and FSH release. products of the testes have a negative feedback on the hypothal and anterior pituitary.

Question 9

prenatal stage of development

Answer 9

leydig cells make up more than half the testes. increase in leydig cells is dependent on maternal chorionic gonadotropin (hCG) in early development and embryonic leutinizing hormone, LH, in late development

Question 10

prior to puberty development

Answer 10

few GnRH pulses and low FSH and LH levels. hypothal and pituitary are very sensitive to negative feedback inhibition by androgens. spermatogonia exist in diploid, undifferentiated form in basal compartment of testes

Question 11

puberty development

Answer 11

frequency and amplitude of GnRH pulses increase. sensitivity of HP axis to negative feedback of testosterone decreases. gonadotroph sensitivity to GnRH increases, LH and FSH production increases. testosterone increases and spermatogenesis begins. androgen driven changes characteristic of puberty occur

Question 12

physiology of leydig cells

Answer 12

has receptors for LH. stimulates G protein coupled receptor to make cAMP and activate PKA. this increases transcription of enzymes involved in testosterone synth, stimulates rate limiting step (cholesterol to pregnenolone), and sterol carried protein and sterol activating protein.

Question 13

Sertoli cell physiology

Answer 13

has receptors for FSH. increases transcription of androgen binding protein which keeps local testosterone levels high, P450 aromatase to produce estrogen, growth factors that support production of sperm, inhibins that suppress leydig cell proliferation and FSH secretion, and factors that act on leydig cells

Question 14

crosstalk between leydig and sertoli cells

Answer 14

leydig cells make testosterone which acts on sertoli cells. leydig makes endorphin which inhibits sertoli cell proliferation. sertoli cells make estrogen which acts on the leydig cells. sertoli cells make growth factors which acts on leydig cells to increase LH receptors

Question 15

kallmann syndrome

Answer 15

hypogonadotropic hypogonadism. lack LH and FSH and have anosmia (inability to smell). patients fail to enter puberty. Genes KAL-1, FGFR1, PROK2, and PROKR2 have been implicated in the disease. mutations prevent neurosensory neurons extending from axons into the brain which prevents migration of GnRH neurons into the hypothalamus

Question 16

androgen synthesis

Answer 16

cholesterol is precursor. made from acetyl coA or taken up from LDL. first step occurs in mitochondria, where P450 side chain cleavage enzyme (desmolase) removes the side chain of cholesterol and produces pregnenolone. this is the rate limiting step and is upregulated by LH.

Question 17

male pseudohermaphroditism

Answer 17

any deficit in the mechanism by which androgens act in genetic males may cause this. potential cause is 5alpha reductase deficiency. this makes dihydrotestosterone (DHT). problems with the enzyme lead to low DHT but normal testosterone. Leads to a failure in DHT dependent development, aka urogenital sinus and external genitalia. develop according to female pattern. wolffian ducts degenerate. normal AMH suppresses mullerian development

Question 18

androgenic effects in general

Answer 18

maturation of sex organs, particularly the penis.
development of secondary sexual characteristics like deepening of voice, growth of beard and axillary hair.
promote protein synth and tissue growth
increase in muscle and strength, bone density and strength, nd maturation
males have larger hearts, lungs, liver, and erythrocytes

Question 19

androgen receptors

Answer 19

free form of testosterone enters cell by diffusion. binds homodimereic receptor. directs transcriptional activity of target genes. DHT binds the same receptor but has greater activity.

Question 20

kennedy’s disease aka spinobulbar muscular atrophy (SBMA)

Answer 20

lower motor neuron disease caused by mutation in the androgen receptor. expansion of a CAG repeat in the gene causes a polyglutamine expansion in the androgen receptor. mutation causes a toxic gain of function. patients display progressive weakness due to degeneration of motor neurons in the brain stem and spinal cord.

Question 21

senescence (andropause)

Answer 21

unlike menopause, no abrupt loss of fertility. testosterone decreases with age especially >40 years. quantity and quality of sperm decreases. FSH and LH increase. reduced testosterone causes some aging problems: decreased bone, muscle mass, apetite, libido, hematocrit.

Question 22

low testosterone

Answer 22

low sex drive, ED, loss of muscle, mood problems, sleep problems, loss of body/facial hair. high percentage of men with symptoms benefit from treatment. men with prostate or breast cancer should not be treated with testosterone.

Question 23

finasteride (propecia)

Answer 23

blocks production of DHT. used to treat male pattern baldness. side effects include impotence, depression, abnormal ejaculation

Question 24

effects of anabolic steroid abuse

Answer 24

reduced sperm count, small testes, boob growth in men, heart liver kidney damage. girls can have body hair and deep voice. causes increase in LDL and decrease in HDL. body doesnt make any of its own testosterone since the body has no FSH or LH

Question 25

interaction of the sertoli cells and sperm

Answer 25

spermatogenesis is initiated at puberty through the action of FSH and LH.

Question 26

spermatozoa development

Answer 26

primary spermatocye -> secondary spermatocyte -> spermatid -> spermatozoa

Question 27

accessory male sex gland function

Answer 27

makes seminal plasmid. plethora of sugars and ions. derived from seminal vesicles, prostate gland, bulbourethral glands.

Question 28

sympathetic nervous system control of erection, emission, and ejaculation

Answer 28

testis, epididymis, male accessory glands and erectile tissue receive parasymp and symp innervation. symp fibers come from T11-L2 of spinal cord and travel through mesenteric, hypogastric and pelvic plexuses and hypogastric and cavernous nerves. responsible for emission and ejaculation. symp tone maintains deumescence

Question 29

parasym control of erection, emission, and ejaculation

Answer 29

fibers come from S2-S4. travel via pelvic nerve to pelvic plexus. post gang fibers reach penile corpora and vasculature through the cavernous nerves. leads to erection (tumescence).

Question 30

action of acetylcholine and NO on vasodilation/erection

Answer 30

under parasymp control. nerve terminals release acetylcholine and NO. NO relaxes smooth muscle and vasodilates arteries. increases intracellular cGMP levels. decrease in symp tone allows for relaxation for corpora. viagara inhibits cGMP degraders, keeping cGMP levels high

Question 31

emission

Answer 31

movement of ejaculate into urethra. sym stim of hypogastric causes contraction of smoooth muscle of epididymus, vas deferens and accessory glands. semen propelled into prostatic urethra. internal sphincter of bladder prevents retrograde sperm flow