Physio 2 - Repro 1

isabellepjk's version from 2017-04-26 03:56

Male Repro

Question Answer
What axis is the male repro system controlled by?The hypothalamic (GnRH) - pituitary (FSH/LH) - Gonadal (testosterone) axis
The hypothalamus is controlled by what nuclei?Before sexual differentiation, there is the TONIC and the SURGE center.
FETAL TESTOSTERONE abolishes the surge center so males have tonic center only
What does the tonic center produce?
What does this product do?
Gonadotropin Releasing Hormone (GnRH), which is released into the portal system and stimulates the ant. pituitary to produce 2 gonadotropins-- LH and FSH.
What is the definition of puberty for a male?(1) age when ejaculate contains a threshold number of sperm for a successful fertilization
(2) display with BEHAVIORAL TRAITS
By what is the onset of puberty controlled?Mostly genetically (age) controlled-- depends on ability of hypothalamus to produce sufficient GnRH to promote/support gametogeness
During/after pubery, the hypothalamus "wakes up" and does what? Results in?It releases GnRH in a PULSATILE fashion (release every 2-6 hrs).
So every 2-6 hrs the ant. pituitary will release a pulse of LH and FSH into the circulation.
What are the two functional compartments (and their fxs) of the testis?(1) tubular compartment (seminiferous tubules, site of spermatogenesis)
(2) interstitial compartment (leydig cells, site of testosterone production)
What does LH do for the male?the LH pulse binds to receptors on the LEYDIG cells which then produce/release TESTOSTERONE
(Luten Leydig)
Explain the testosterone conversion?
What is testosterone essential for?
After LH binds to leydigs which releases Testosterone, the testosterone diffuses into the Sertoli cells and is converted into the active DIHYDROTESTOSTERONE (DHT) and partly into ESTRADIOL (E2), which stimulates/maintains spermatogenesis.
(LH + Leydigs = Testosterone --> sertoli cells --> DHT + E2)
Which hormone is essential to stimulate/maintain spermatogenesis?Testosterone
What is DHT?Dihydrotestosterone- after testosterone is released from leydig cells, the sertoli cells convert the Testosterone into DHT (And estradiol)
What does FSH do for males?FSH binds to receptors on SERTOLI cells which then produce SPERMATOGENIC SUBSTANCES and INHIBIN
What are/what do spermatogenic substances do? (what are they from)(Are made when FSH binds to sertoli cells)
They MAINTAIN SPERMATOGENESIS. There is *ABP (androgen binding protein) which maintains high tubular Testosterone conc. despite pulsatile release.
Also present are activin, opioids, growth factors, oxytocin, prostaglandins, nutrient-binding proteins (fxns not fully understood)
Inhibin selectively inhibits FSH release
What is the function of Inhibin? Where did it come from?It selectively INHIBITS FSH RELEASE (When FSH from the FSH pulse binds to sertolis, they make inhibin and spermatogenic substances)
What is the neg. feed back mechanism involved in the pulsatile release of GnRH/FSH/LH?Testosterone, estrogen, and Inhibin enable PULSATILE release of GnRH, LH, FSH
(permanent release would lead to receptor down regulation)
Sexual stimulation starts with what?
Which nerves are involved?
Sensory (olfactory, auditory, visual) and psychic stimuli --> erection center (sacral spinal cord) --> pelvic nerves
How does the animal produce an erection?Relax penile arteries and corpus cavernosus to inc blood flow.
Contraction of ischiocavernousus mm to compress penis and reduce outflow,
Relax retractor penis mm --> this inc the pressure and causes hardening
Where is the erection center? Where is the ejaculation center?Erection= sacral spinal cord.
Ejaculation center= lumbar spinal cord.
How does emission/ejaculation occur?Increase tactile sensation-->
Transmission to ejaculation center (lumbar sc)-->
Pudendal nn and posterior pituitary gland-->
Release oxytocin. This leads to contraction of the vas deferens and accessory gland mm, releasing sperm and fluids into urethra (THIS IS EMISSION).
Then inc urethral pressure leads to rhythmic contractions of urethra and trunk mm--> EJACULATION
How is locking of dogs achieved? Why lock?Contraction of sphincter mm of vulva, the bulbus glandis of penis remains engorged, MAYBE shifting of os penis. Locking facilitates uterine rather than vaginal insemination as the second stage of coitus produces a lot of seminal fluid
What kind of metabolic effect do androgens have?ANABOLIC. esp. protein metabolism. So increased metabolic rate, mm growth, bone thickness, skin thickness, hair growth
What happens if you give animals androgens?Constant high testosterone levels inhibit GnRH, inhibit LH/FSH--> lack of devolopment/testicular fxn.
(LH is for making testosterone from leydig cells, FSH for sertolis to make spermatogenic substances and inhibin)
Main influences for seasonal breeders? what happens when not in season?PHOTOPERIOD (also ambient temp).
Not in season leads to testes/spermatogenesis/Testosterone production regression.
For sheep this is complete infertility, for stallions, it is reduced.
What gland often controls seasonal breeders?Pineal Gland
What is a long day breeder? What are some examples? What happens to make them start?Spring/summer time breeding.
Horses, cats.
Inc light--> pineal gland--> **DEC melatonin--> inc GnRH
What is a short day breeder? What are some examples? What happens to make them start?Goat/sheep/deer.
Breed during autumn/early winter.
Dec light--> pineal-->INC opioids (?)/Kisspeptin -->inc GnRH release--> stim spermatogenesis and female cycles (possibly regulated via hypothalamic KISS-peptin)
If you give a horse anabolic steroids, why would it be a shitty breeder?Constant increase in testosterone before/during puberty-->
Suppress hypothalamic tonic center-->
Not enough GnRH-->
Not enough LH/FSH-->
Insufficient growth of testes, esp. sertoli cells-->
Testes small and insufficient sperm produced, despite enough testosterone to maintain libido.