Lecture 4+5 Flashcards
Male parts that are dually innervated (para/symp):
Testes
Epididymis
Accessory glands
Erectile tissue
Nerve that innervates penis:
Pudendal nerve. Somatic afferent and efferent.
Pathways of erectile regulation:
Parasymp: pelvic nerve.
Symp: right/left hypogastric nerves.
Somatic: pudendal nerve.
Parasympathetic component of erection:
Coordinated by corpus cavernosa and corpus spongiosum.
Corpora smooth muscle relaxes and allows increased inflow of blood. Parasymp post-gang release of ACh and NO.
ACh binds to M3 receptors on endothelial cells.
PLC pathway to make NO. NO diffuses to vascular smooth muscle to stimulate vasodilation.
Sympathetic component of erection:
Sympathetic tone decreases to allow relaxation. Don’t want to cancel out parasymp.
Somatic component of erection:
Two kinds of striated muscle:
- Ischiocavernous: contracts during final phase of erection to increase cavernosa pressure above systemic arterial pressure.
- Bulbospongiosus: increases spongiosum engorgement by pumping blood from underlying penile bulb.
Seminal emission:
Mostly sympathetic.
Coordinated peristalsis of vas deferens, seminal vesicles, prostatic smooth muscle.
Internal sphincter of bladder constricts to stop retrograde ejaculation.
Drugs to treat erectile dysfunction:
Sildenafil (Viagra), vardenafil (Levitral), tadalafil (Cialis).
Oral drugs that promote smooth muscle relaxation by preventing cGMP degradation. Highly selective and high affinity inhibitors of cGMP-specific phosphodiesterase 5.
Side effects of sildenafil:
Blue vision. cGMP is needed to see blue; viagra blocks cGMP breakdown.
Causes of retrograde ejaculation:
Drugs that interfere with sympathetic tone.
Diabetes, MS.
Nerve damage.
Interrupted innervation of vas deferens or bladder neck.
Treatment of retrograde ejaculation:
Sympathomimetic drugs (phentolamine, ephedrine, imipramine). Increase tone of vas deferens and sphincter.
Hilus of female reproductive system:
The place where the ovary cortex doesn’t surround the medulla.
Frigging ovarian cycle:
Lecture 4/5, slide 14
Changes in gonadotropins during puberty:
GnRH becomes pulsatile and gonadotropins are harder to inhibit by estrogen. Hyp-pit axis gets resistant to inhibition by sex steroids. Gonadotropins are UNSTOPPABLE during adulthood.
Pulsatile GnRH release:
Once an hour. In early follicular phase, sensitivity is low and gonadotropin surge is small. In late follicular phase, sensitivity rises and gonadotropin surge gets bigger.
Halflife of GnRH:
2-4 minutes.
Pulse generator for GnRH release:
Located in arcuate nucleus of hypothalamus.
Why is GnRH release pulsatile?
Pulsatile favours increased GnRH receptors in gonadotrophs. Continuous administration causes downregulation of GnRH receptors.
Granulosa cell function during luteal phase:
Granulosa cells can do everything that Theca cells can! wow. cool.
GnRH receptor replenishment:
Receptor is internalized and partially degraded in lysosomes. A part of the receptor is then shuttled back to the surface for reuse.
Negative feedback control of ovarian steroids: most of the cycle.
Estrogen from ovaries inhibits hypothalamus and ant pit gonadotrophs at high and low concentrations.
Progestins from ovaries inhibit hypothalamus and ant pit gonadotrophs only at high concentrations.
Positive feedback control of ovarian steroids: end of follicular phase.
At high enough estrogen concentrations, hyp-pit axis reverses sensitivity to estrogen. Estrogen now stimulates GnRH gonadotrophs, leading to LH surge.
What molecules inhibit arcuate nucleus? preoptic area?
Arcuate nucleus: opiates
Preoptic area: GABA
Negative feedback control of ovarian steroids by inhibins:
Inhibit FSH from ant pit gonadotrophs at mRNA level. No effect on LH. Decreases androgen production, which decreases estrogen.
Positive feedback control of ovarian steroids by activins:
Promotes FSH transcription. No effect on LH. Stimulates estrogen.
Therapeutic uses of GnRH:
To increase gonadotropin, treat with pulsatile. To inhibit gonads, treat with continuous administration.