RMP of smooth muscle is?
**Core Concept**
The resting membrane potential (RMP) of smooth muscle cells is generated by the distribution and permeability of ions across the cell membrane, particularly **potassium (K+)** and **sodium (Na+)** ions. This potential difference is crucial for the regulation of smooth muscle contraction and relaxation. The RMP is influenced by various factors, including ion channels and pumps.
**Why the Correct Answer is Right**
The correct answer is related to the fact that smooth muscle cells have a unique electrical properties, with a RMP that is typically around -50 to -60 millivolts (mV), due to a high permeability to **potassium ions**. This is because **potassium channels** are open at rest, allowing K+ ions to leave the cell, which creates a negative charge inside the cell.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the RMP of smooth muscle is not as negative as -80 mV, which is more typical of skeletal muscle cells.
**Option B:** This option is incorrect because the RMP of smooth muscle is not as positive as 0 mV.
**Option D:** This option is incorrect because the RMP of smooth muscle is not as negative as -90 mV.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the RMP of smooth muscle cells can vary depending on the location and type of smooth muscle, and that changes in RMP can affect contraction and relaxation of smooth muscle.
**Correct Answer:** D. -60 mV