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Repro psio 2

QuestionAnswer
What is erectile dysfunction? Erectile dysfunction is the inability to achieve and maintain an erection sufficient for sexual intercourse.
What are the major categories of causes of ED? Psychogenic (stress, anxiety, depression) Neurogenic (nerve damage, spinal cord injury) Hormonal (low testosterone) Vascular (diabetes, hypertension, atherosclerosis) Drug-induced (antidepressants, antihypertensives) Aging / chronic disease
What is the relationship between calcium and smooth muscle? ↑ Calcium → smooth muscle contraction ↓ Calcium → smooth muscle relaxation
What happens to cytosolic calcium during erection? Cytosolic calcium decreases, allowing smooth muscle relaxation and erection.
What causes smooth muscle contraction? Contraction occurs when myosin binds actin, which requires phosphorylation of the myosin regulatory light chain (MLCK)
Describe the smooth muscle contraction pathway. Cytosolic Ca²⁺ increases Ca²⁺ binds calmodulin Ca²⁺–calmodulin activates MLCK MLCK phosphorylates myosin light chain Myosin binds actin Cross-bridge cycling → contraction 📌 Mnemonic: Ca → Calm → Kinase → Contract
How does smooth muscle relaxation occur? When cytosolic calcium is low, myosin phosphatase dephosphorylates the myosin light chain, preventing actin binding and causing relaxation.
Define tumescence and detumescence. Tumescence: erection caused by smooth muscle relaxation Detumescence: return to flaccid state caused by smooth muscle contraction
How does sympathetic stimulation cause detumescence? Norepinephrine released Activates α₁ receptors Gq protein activated IP₃ produced Ca²⁺ released from ER Cytosolic Ca²⁺ rises Smooth muscle contracts → flaccid penis 📌 Memory hook: Stress kills erections
How does parasympathetic stimulation cause erection? Acetylcholine released Endothelial cells activated eNOS & nNOS produce nitric oxide (NO) NO activates guanylyl cyclase cGMP increases cGMP lowers Ca²⁺ MLCK inactivated Smooth muscle relaxes → erection
What is the role of nitric oxide in erection? Nitric oxide activates guanylyl cyclase, increasing cGMP, which lowers cytosolic calcium and causes smooth muscle relaxation.
What is the secondary pathway that supports smooth muscle relaxation? Prostaglandin E₁ activates a Gs-coupled receptor → adenylyl cyclase → cAMP → protein kinases → ↓ Ca²⁺ → relaxation.
What is phosphodiesterase-5 (PDE5)? PDE5 is an enzyme that breaks down cGMP into 5′-GMP, terminating smooth muscle relaxation and contributing to detumescence.
Do PDE5 inhibitors cause erections? No. PDE5 inhibitors maintain erections but do not initiate them. Sexual stimulation and NO release are still required.
Name three PDE5 inhibitors (generic + brand). Sildenafil — Viagra Vardenafil — Levitra Tadalafil — Cialis
What does IC₅₀ mean? IC₅₀ is the concentration of a drug required to inhibit 50% of enzyme activity. Lower IC₅₀ = higher potency.
Which PDE isoform is sildenafil most selective for? Sildenafil is most selective for PDE5, which is abundant in the corpus cavernosum.
Why can sildenafil cause visual disturbances? Sildenafil has relatively low selectivity for PDE6, which is present in the retina. Inhibition of PDE6 can disrupt visual signaling.
Why are PDE5 inhibitors contraindicated with nitrites? Both increase nitric oxide signaling → excessive vasodilation → severe drop in blood pressure → risk of fainting, stroke, or heart attack.
What is priapism and how is it treated? Priapism is a prolonged, painful erection lasting >4 hours. It is treated with phenylephrine, an α₁-agonist that causes smooth muscle contraction.
What is alprostadil and how does it work? Alprostadil is a synthetic prostaglandin E₁ that increases cAMP, lowers calcium, and causes smooth muscle relaxation via a pathway independent of NO/cGMP. Delivery methods: Transurethral pellet Intracavernosal injection
Created by: bythedeli
 

 



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