## Core Concept
The question pertains to the cellular mechanism of calcium release, specifically focusing on the channel responsible for this process. **Calcium channels** and **ryanodine receptors** play critical roles in calcium homeostasis within cells, particularly in muscle cells and neurons. The release of calcium from intracellular stores is crucial for various cellular functions, including muscle contraction and neurotransmitter release.

## Why the Correct Answer is Right
The correct answer, **Ryanodine receptor (RyR)**, is a type of channel that releases calcium from intracellular stores, particularly from the sarcoplasmic reticulum in muscle cells. Ryanodine receptors are essential for excitation-contraction coupling in skeletal and cardiac muscles. They are activated by increased intracellular calcium levels, leading to a significant release of calcium into the cytosol, which then triggers muscle contraction.

## Why Each Wrong Option is Incorrect
- **Option A:** Voltage-gated calcium channels are primarily responsible for the influx of calcium ions into the cell from the extracellular space, not the release from intracellular stores.
- **Option B:** While certain types of channels and receptors can influence calcium levels indirectly, the **IP3 receptor** is directly involved in releasing calcium from the endoplasmic reticulum in response to inositol trisphosphate (IP3) signaling, not specifically what the question seems to point towards with the correct answer focusing on a channel.
- **Option D:** This option does not directly relate to well-known calcium channels or receptors responsible for calcium release.

## Clinical Pearl / High-Yield Fact
A crucial point to remember is that **ryanodine receptors** are targets for certain drugs and are implicated in malignant hyperthermia, a life-threatening medical emergency. Mutations in the genes encoding ryanodine receptors can lead to this condition, highlighting the clinical significance of understanding calcium release mechanisms.

## Correct Answer Line
**Correct Answer: C. Ryanodine receptor.**