26

Physiology of Penile Erection and

Pathophysiology of Erectile

Dysfunction

Tom F. Lue

Questions

1.Penile prosthesis tends to extrude more on the:

a.lateral surface.

b.ventral surface.

c.crura.

d.glans.

e.dorsal surface.

2.Accessory pudendal artery is most likely to arise from:

a.external iliac artery.

b.femoral artery.

c.obturator artery.

d.superior vesical artery.

e.bulbourethral artery.

3.During a rigid erection, all the following statements are true EXCEPT:

a.dilation of the arterioles and arteries.

b.sinusoidal relaxation.

c.corporal pressure increase (to several hundred millimeters of mercury).

d.subtunical venous compression reducing venous outflow.

e.relaxation of the ischiocavernosus muscles.

4.All of the following are neurotransmitters that promote sexual function EXCEPT:

a.dopamine.

b.acetylcholine.

c.oxytocin.

d.serotonin (5-HT).

e.nitric oxide (NO).

5.All of the following statements are true EXCEPT:

a.NO stimulates the production of cyclic guanosine monophosphate (cGMP).

b.NO released by endothelial nitric oxide synthase (eNOS) contained in the terminals of the cavernous nerve initiates the erection process, whereas nitric oxide released from neuronal nitric oxide synthase (nNOS) in the endothelium helps maintain erection.

c.Cyclic GMP activates protein kinase G, which in turn opens the potassium channels and closes the calcium channels.

d.Low cytosolic calcium favors smooth muscle relaxation.

e.The smooth muscle regains its tone when cGMP is degraded by phosphodiesterase.

6.All the following statements about testosterone are true EXCEPT:

a.It enhances sexual interest.

b.It increases the frequency of sexual acts.

c.It increases the frequency of nocturnal erection.

d.It increases visually stimulated erections.

e.It increases bone density and lean body mass.

7.All the following antihypertensives DO NOT negatively affect erection EXCEPT:

a.hydrochlorothiazide.

b.terazosin.

c.losartan.

d.amlodipine.

e.captopril.

8.All of the following are possible causes of erectile dysfunction (ED) in endstage renal disease (ESRD) patients EXCEPT:

a.low NO.

b.neuropathy.

c.low prolactin.

d.atherosclerosis.

e.depression.

9.All of the following statements are true EXCEPT:

a.NO is the principal neurotransmitter mediating penile erection.

b.Oxytocin is a potent inducer of erection when injected into the central nervous system.

c.Central norepinephrine transmission has a positive effect on sexual function.

d.GABAB receptors are proerectile.

e.Cannabinoid CB1 receptor activation inhibits sexual function.

.All the following statements about smooth muscle contraction are true EXCEPT:

a.Myosin light chain phosphatase (MLCP) is a holoenzyme consisting of a type 1 phosphatase (PP1c), a myosin-targeting subunit (MYPT1), and a 20-kDa subunit of unknown function.

b.MLCP inhibition may lead to enhanced smooth muscle contraction.

c.Phosphorylation of the regulatory subunit of MLCP by Rho kinase inhibits phosphatase activity and enhances the contractile response.

d.One of the mechanisms of increased intracellular Ca2 + is by permitting entry of extracellular Ca2 + through receptor-operated channels without a change in membrane potential.

e.Latch state refers to a period of smooth muscle relaxation after prolonged contraction.

.All of the following are true statements about NO EXCEPT:

a.Synthesis of NO is catalyzed by NOS, which converts l-arginine and oxygen to l-citrulline and NO.

b.Upregulation of nNOS expression has been found in the corpus cavernosum of aging and diabetic rats.

c.NOS exists as three isoforms in mammals: nNOS, inducible nitric oxide synthase (iNOS), and eNOS.

d.Gene transfer of nNOS or eNOS to the penis has been shown to augment erectile responses in aging rats.

e.Gene transfer of iNOS has enhanced intracavernous pressure.

.All the following statements are true EXCEPT:

a.C-type natriuretic peptide (CNP) is the most potent natriuretic peptide and it relaxes the isolated cavernous smooth muscle by binding to NPR-B.

b.Protein kinase G-I (PKGI) may induce relaxation via activation of the plasma membrane Ca2 +-ATPase pump, inhibition of IP3 generation, inhibition of Rho-kinase, stimulation of MLCP, and phosphorylation of heat shock proteins.

c.Reduced penile adenosine levels are associated with priapism.

d.Calcitonin gene-related peptide is a potent vasodilator released from perivascular nerve fibers.

e.The erectogenic effects of PGE1 as a pharmaceutic agent have been

extensively documented.

.All of the following statements about ED are true EXCEPT:

a.Psychogenic ED is the most common form of ED.

b.10% to 19% of cases of ED are neurogenic.

c.In cases of pelvic fracture, ED can be a result of cavernous nerve injury or vascular insufficiency or both.

d.There is a decrease in penile tactile sensitivity with increasing age.

e.In diabetics, impairment of neurogenic and endothelium-dependent

relaxation results in inadequate NO release.

.All of the following statements about arteriogenic ED are true EXCEPT:

a.Atherosclerotic or traumatic arterial occlusive disease can decrease the perfusion pressure and arterial flow to the sinusoidal spaces.

b.Common risk factors associated with arterial insufficiency include hypertension, hyperlipidemia, cigarette smoking, diabetes mellitus, blunt perineal or pelvic trauma, and pelvic irradiation.

c.Long-distance cycling is also a risk factor for vasculogenic and neurogenic ED.

d.Lesions in the pudendal arteries are less common in men with ED than in the general population of similar age.

e.Among men with coronary arterial disease, the prevalence of ED increases while the severity of coronary arterial lesions increases.

.All of the following statements are true EXCEPT:

a.Aging is the single most important contributing factor to ED.

b.The aging process can affect the central regulatory mechanism, hormonal and neural function, and penile structure.

c.Diabetes mellitus and metabolic syndrome may affect multiple organ systems and cause premature aging of both central and peripheral structures and molecules that regulate erectile process.

d.Primary ED may be due to psychogenic cause, inexperience, congenital arterial insufficiency or abnormal venous channels.

e.Primary ED refers to a recently developed ED of unknown etiology.