Repro Physl 4 Flashcards
What happens to the vascular in response to sexual excitation?
Dilation of the small arteries and engorgement of vascular compartments
What does the engorgement of the vascular compartments do?
Causes passive compression of adjacent veins
What causes the contraction in the erect state?
Noradrenaline
What causes the relaxation in an erect state?
Acetylcholine from parasympathetic nerves
What is the dominant input to the small arteries that supply the penile tissue at rest?
Sympathetic
What is the main transmitter being released by sympathetic nerves onto the penile arteries at rest?
Norepinephrine from sympathetic nerves
What is the effect of sexual arousal on the inputs to the penis?
- Sympathetic input is inhibited during erection
* Neurons that release nitric oxide increase
What causes the net vasodilation in the net vasodilation in an erection?
The decrease of sympathetic stimulation and the release of NO
What are the four primary stimulus for an erection?
- Mechanoreceptors in the head of a penis
- Increased afferent neural firing
- Spinal reflex in lower spinal cord
- Controls efferent neural outflow
What is ejaculation controlled by?
Its a spinal reflex controlled by afferent pathways from penile mechanoreceptors
What are the two phases of ejaculation?
- Emission
* Ejaculation
What occurs in emission?
Sympathetically mediated contraction of the epididymis, vas deferens, ejaculatory ducts, prostate and seminal vesicles
What occurs in ejaculation?
Semen is expelled from the urethra by a rapid contraction of urethral smooth muscle and skeletal muscle at the base of the penis
What part of the NS is emission mediated from?
The sympathetic NS which is opposite from erection which inhibits the sympathetic input
What are some treatment options for ED?
- Increasing Nitric Oxide through PDE5 inhibitors
* Prostaglandins
How does NO act in ED?
It elicits the release of cGMP which decreases calcium levels which promotes smooth muscle relaxation of the blood vessels which increases blood flow to the penile tissue
What is cGMP which is activated by NO broken down by?
PDE5
How do PDE5 inhibitors work?
They inhibit PDE5 which inhibits the breakdown of cGMP which can go on to decrease calcium and increase muscle relaxation
How can Prostaglandins help with ED?
PGE1 binds to the prostaglandin receptor and through an AC pathway will decrease intracellular calcium and increase vasodilation
What does the prostate convert testosterone to?
DHT by 5 alpha-reductase
What converts testosterone to estradiol (estrogen) and by what?
Brain, liver, and adipose tissue by aromatase
What happens if there is decreased testicular function/testosterone synthesis?
- Accessory organs decrease in size
- Glands reduce secretion rates
- Smooth muscle activity ducts is decreases
- Sex drive, erection and ejaculation impaired
- Mitigated by testosterone treatment
What are the first signs of puberty in males due to?
Secretion of adrenal androgens under the influence of ACTH
What do the adrenal androgens support during puberty?
The development of pubic and axillary hair
Why don’t the testes produce a lot of testosterone before puberty?
There is strong suppression of GnRH and gonadotropin release
What is a theory to what puberty occurs?
Kisspeptin neurons in the hypothalamus is upstream of the GnRH containing neurons is activated which leads to an increased GnRH and reduced sensitivity to negative feedback
What are the secondary sex characteristics of males dependant on?
Testosterone and DHT
What do the secondary sex characteristics do?
- Include growth of the larynx, thick secretion of skin and oil glands
- Masculine fat distribution
How do androgens stimulate bone growth?
By stimulating GH secretion
Why can androgens be considered anabolic steroids?
Because they have a stimulatory effect for protein synthesis in muscle
Why do males have an increased hematocrit?
Because androgens stimulate erythropoietin from the kidneys
What are the positives to anabolic steroid use?
Increased muscle mass and athletic performance
What are the negative effects of anabolic steroids?
- Overstimulation of the prostate
- Aggression
- Decreased GnRH, LH and FSH
Why don’t anabolic steroid increase sperm production?
Because they cannot cross the blood-testis barrier and access the Sertoli cells
What is Hypogonadism?
The reduction of testosterone release from the testes
What is Primary hypogonadism related to?
Testicular failure
What is Secondary hypogonadism related to?
Failure to supply testes with gonadotrophic stimulus. So this is a problem with either the pituitary or the hypothalamus
What are the gonadotropin levels in primary hypogonadism?
There is sufficient gonadotropin levels
What are the gonadotropin levels in secondary hypogonadism?
There is low gonadotropin levels. So low LH, FSH and testosterone
What is the most common genetic cause of primary hypogonadism?
Klinefelter’s syndrome
What is the genotype of Klinefelter syndrome?
XXY
What is the appearance of people with Klinefelters syndrome?
They have small poorly developed testes and long arm span
How are Leydig and Sertoli cells affected by Klinefleter’s syndrome?
There is insufficient Leydig and Sertoli cell function so no sperm production or development of seminiferous tubules
How are secondary sex characteristics affected by Klinefelters?
There is absence of them and an increased breast size
Why is there high LH and FSH in Klinefelter’s primary hypogonadism?
Because there is a loss of inhibin and negative feedback that would’ve acted on the hypothalamus and anterior pituitary
How are LH and FSH affected by secondary hypogonadism?
Their production is decreased
How does Hyperprolactinemia cause secondary hypogonadism?
Pituitary cells release prolactin and excessive production can cause high levels of prolactin which has strong negative feedback effect on gonadotropin release from the anterior pituitary
How does Hypopituitarism cause secondary hypogonadism?
A loss of anterior pituitary gland function
What would happen if the testes are removed after puberty?
They would still have secondary sex characteristics but they would have atrophy of androgen-sensitive tissue
Why is there a testosterone in andropause?
Because of the deterioration of testosterone levels
