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