Erection and ED Flashcards
List components of the heomdynamic response of the corpora cavernosa that allow for erection
- dilation of arterioles and increased blood flow
- trapping of incoming blood by sinusoids
- compression of subtunical venular plexuses to reduce venous outflow
- stretching of tunica to occlude emissary veins
- increased oxygen tension and intracavernous pressure
- increase in pressure through contraction of ischiocavernosus muscles
The corpus spongiosum achieves a pressure only about 1/2 that of the corpus cavernosa because of lower __________
venous occlusion
Sympathetic and parasympathetic nerves merge to form the _________, which enter the corpora cavernosa and spongiosum to direct erection and detumescence.
cavernous nerves
The somatic nerves of the penis are responsible for sensation and for contraction of the ___________ and _________ muscles
bulbocavernosus and ischiocavernosus
Where do sympathetic nerves to the penis arise from?
T10-T12
Where do parasympathetic nerves to the penis arise from?
S2, 3, 4
The sensory fibers from the penis converge to form the dorsal nerve of the penis then join with other nerves to become the _________
pudendal nerve
What are the supra-spinal centers of penile erection?
pre-optic area, paraventricular nucleus of hypothalamus and hippocampus
Smooth muscle contraction and relaxation in the penis are regulated by cytosolic _______
free caclium
Smooth muscle contraction is required for ______; smooth muscle relaxation is required for ________
contraction= detumescence relaxation= erection
Describe the molecular mechanism of smooth muscle contraction in the penis
- Elevated levels of calcium causes binding to calmodulin and exposes sites of interaction with myosin light-chain kinase
- cycling of myosin crossbridges along actin filaments generates force
- myosin ATPase hydrolyzes ATP to provide energy for contraction
Describe the molecular mechanism of smooth muscle relaxation in the penis
- decrease in sarcoplasmic calcium causes calmodulin dissociation from myosin light-chain kinase
- dephosphorylation of myosin and detachment from the actin filament results in muscle relaxation
Cyclic GMP and cAMP are the secondary messengers involved in smooth muscle relaxation
List general categories of causes of ED
psychogenic neurogenic endocrinologic arteriogenic venogenic
List elements of a history that suggest psychogenic ED
- young, healthy patients
- sudden onset
- situation or partner specific
- nocturnal erections preserved
Describe possible mechanisms of psychogenic ED
Direct inhibition of the spinal erection center as an exaggeration of normal suprasacral inhibition and sympathetic outflow
Elevated peripheral catecholamine levels preventing relaxation of smooth muscle
List some possible causes of neurogenic ED
- pathology in preoptic area, paraventricular nucleus, hippocampus
- Parkinson’s
- stroke
- epilepsy
- Alzheimer’s
- trauma
- spinal cord injuries or pathology
What effects do androgens have on libido?
increased sexual interest
increased frequency of sex
increased nocturnal erections
Describe the effect of testosterone on ED
Below a threshold of about 200, low testosterone could contribute to ED
List endocrinologic causes of ED
- hypogonadotropic or hypergonadotropic hypogonadism
- hyperprolactinemia
- hypothyroidisim
What are risk factors for arteriogenic causes of ED
Hypertension, hyperlipidemia, smoking, diabetes, trauma, irradiation
Differentiate atheroslcerotic vs traumatic arteriogenic ED
- atherosclerosis: narrowing is diffuse along the internal pudendal, common penile, cavernous arteries
- trauma: can have a focal lesion that is amenable to surgery
How does venogenic ED present?
inability to maintain erection despite ability to achieve tumescence and some rigidity
What drugs can contribute to ED?
- drugs of abuse- alcohol, tobacco, marijuana, cocaine
- anti-HTN especially thiazides, B blockers
- CNS: sedatives, SSRIs, anlagesics
- Histamine receptor blockers
- GnRH agonists, estrogen
What is first line treatment for ED?
PDE5 inhibitors
vacuum constriction devices
What is the mechanism of action of PDE inhibitors?
inhibit PDE5, increasing cGMP and promoting and sustaining smooth muscle relaxation
What is second line therapy for ED?
intracavernosal therapy
What patients are candidates for penile prostheses?
failed vacuum assist devices, medical therapy
What non-pharmacologic approaches may be helpful in ED?
reduce fat, cholesterol, alcohol, tobacco, drugs
weight loss and exercise