31.10
男性性反应：勃起和射精
性刺激可以有各种形式，例如身体接触和视觉或听觉方面的刺激。当这种情况发生时，脊髓骶骨部分的副交感神经反射被激活。这种反射刺激一氧化氮 (NO) 的释放，然后扩张阴茎中的小动脉，增加流向勃起组织（阴茎海绵体和尿道海绵体）的血流量。
充满勃起组织的血液会压迫静脉，这有助于防止血液离开阴茎并导致勃起。当性…
在性刺激作用下，副交感神经元促进局部一氧化氮（NO）的释放，使阴茎内的小动脉扩张，从而增加血液流入阴茎勃起组织——阴茎海绵体和阴茎海绵体。
充盈勃起组织的血液会压迫静脉，阻止血液从阴茎流出。
因此，阴茎会充血并变硬，从而导致勃起。
在性兴奋的关键时刻，由腰部交感神经纤维协调的脊髓反射会引发射精。
该反射可引起附睾、输精管、精囊和前列腺的协调性收缩，将精液推进至前列腺部尿道。
精液进入尿道后，骨盆底的球海绵体肌和坐骨海绵体肌等肌肉会发生收缩。
这些导管、腺体和肌肉的收缩将精液有力地从尿道排出体外，该过程称为射精。
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Q1: How does nitric oxide cause an erection?
Sexual stimulation activates parasympathetic neurons that release nitric oxide in the penis. Nitric oxide dilates the arterioles, increasing blood flow into the erectile tissues—the corpora cavernosa and corpus spongiosum. The blood filling these tissues compresses the veins, preventing blood from leaving and causing the penis to become engorged and rigid.
Q2: What role do the accessory glands play in ejaculation?
During ejaculation, a sympathetic reflex triggers coordinated contractions of the accessory glands of the male reproductive system, including the seminal vesicles and prostate gland. These contractions propel semen into the prostatic urethra in a process called emission, which precedes the forceful expulsion of semen from the body.
Q3: What is the difference between emission and ejaculation?
Emission occurs when sympathetic fibers in the lumbar spine trigger contractions of the epididymis, vasa deferens, seminal vesicles, and prostate, propelling semen into the prostatic urethra. Ejaculation follows when pelvic floor muscles like the bulbospongiosus and ischiocavernosus contract, forcefully expelling semen from the urethra to the exterior.
Q4: Which spinal nerves control the male sexual response?
Parasympathetic fibers in the sacral portion of the spinal cord initiate erection by stimulating nitric oxide release. Sympathetic fibers located in the lumbar region, typically at T12-L2, coordinate the reflex that triggers ejaculation through contractions of reproductive ducts and glands.
Q5: How do pelvic floor muscles contribute to ejaculation?
During ejaculation, pelvic floor muscles including the bulbospongiosus and ischiocavernosus contract forcefully around the urethra. These muscular contractions expel semen from the penis to the exterior, completing the ejaculatory process after semen has entered from the accessory ducts of the male reproductive system.
Q6: What prevents blood from leaving the penis during an erection?
As blood fills the erectile tissues—the corpora cavernosa and corpus spongiosum—it exerts pressure that compresses the veins in the penis. This compression prevents venous outflow, trapping blood within the erectile tissues and maintaining the rigid, engorged state characteristic of an erection.
Q7: What types of sexual stimuli trigger the parasympathetic reflex?
Sexual stimulation can take various forms, including physical touch and visual or auditory cues. Any of these stimuli activate the parasympathetic reflex in the sacral portion of the spinal cord, which initiates nitric oxide release and the cascade of physiological events leading to erection.