True about nervi erigentes are all except ?
**Core Concept**
The nervi erigentes, also known as the pelvic splanchnic nerves, are a pair of nerves that play a crucial role in the autonomic control of the urinary and reproductive systems. They originate from the sacral spinal cord (S2-S4) and transmit parasympathetic signals to the bladder, prostate, and other pelvic organs.
**Why the Correct Answer is Right**
The nervi erigentes are responsible for the parasympathetic innervation of the urinary and reproductive systems. They release acetylcholine, which stimulates the contraction of the detrusor muscle in the bladder, promoting urination. In the context of erection, the nervi erigentes stimulate the release of nitric oxide, leading to smooth muscle relaxation and increased blood flow to the penis.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because the nervi erigentes do indeed originate from the sacral spinal cord (S2-S4).
* **Option B:** Incorrect because the nervi erigentes are responsible for the parasympathetic innervation of the urinary and reproductive systems, not the sympathetic innervation.
* **Option C:** Incorrect because the nervi erigentes do indeed play a role in the regulation of erection, although this is primarily through the release of nitric oxide.
**Clinical Pearl / High-Yield Fact**
Damage to the nervi erigentes can lead to neurogenic bladder and erectile dysfunction. It is essential to identify and manage any potential damage to these nerves during pelvic surgery to prevent long-term complications.
**Correct Answer:** B. The nervi erigentes are responsible for parasympathetic innervation of the urinary and reproductive systems.