**Core Concept**
Insulin plays a crucial role in regulating glucose uptake in myocytes (muscle cells). The glucose transporter responsible for facilitating glucose entry into myocytes in response to insulin stimulation is a specific type of glucose transporter. This transporter is essential for maintaining blood glucose levels and providing energy to the muscle cells.

**Why the Correct Answer is Right**
The glucose transporter in myocytes stimulated by insulin is **GLUT4**. When insulin binds to its receptor on the surface of myocytes, it triggers a signaling cascade that ultimately leads to the translocation of GLUT4 from intracellular vesicles to the plasma membrane. This increases the number of GLUT4 molecules available for glucose transport, allowing glucose to enter the myocytes. GLUT4 is a member of the facilitative glucose transporter family and is primarily expressed in adipose tissue and myocytes.

**Why Each Wrong Option is Incorrect**
**Option A:** GLUT1 is a constitutively expressed glucose transporter found in many cell types, including red blood cells. It is not specifically stimulated by insulin.
**Option B:** GLUT2 is a glucose transporter found in the liver, pancreas, and kidneys. It is involved in glucose sensing and is not primarily responsible for insulin-stimulated glucose uptake in myocytes.
**Option C:** GLUT3 is a high-affinity glucose transporter found in neurons and is not specifically stimulated by insulin.

**Clinical Pearl / High-Yield Fact**
Insulin resistance, which can lead to type 2 diabetes, is often characterized by impaired GLUT4 translocation and glucose uptake in myocytes.

**Correct Answer: C. GLUT4**