Distinguish single-unit and multi-unit smooth muscle with examples.

• A. Multi-unit smooth muscle functions as a syncytium via gap junctions; examples include intestinal wall and uterus.
• B. Single-unit (visceral) smooth muscle functions as a syncytium via gap junctions; examples include intestinal wall and uterus; multi-unit smooth muscle has independent fibers (e.g., iris and airways).
• C. Both types function identically with identical electrical coupling.
• D. Smooth muscle does not use gap junctions.

Answer: (B)