**Core Concept**
An electrical synapse, also known as a gap junction, is a specialized type of synapse that allows for direct electrical communication between two neurons, whereas a chemical synapse relies on neurotransmitters to transmit signals. This fundamental difference in communication mechanisms is crucial in understanding how these two types of synapses function.

**Why the Correct Answer is Right**
In an electrical synapse, gap junction channels allow for the direct passage of ions and small molecules between the cells, enabling rapid transmission of electrical signals. This is in contrast to chemical synapses, where neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, triggering a chemical signal. The presence of gap junctions in electrical synapses eliminates the need for neurotransmitters, allowing for faster and more efficient signal transmission.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because electrical synapses do involve a physical connection between cells, but it's not the primary mechanism of signal transmission.
**Option B:** This option is incorrect because chemical synapses do involve neurotransmitters, but they are released and bind to receptors on the postsynaptic neuron, not transmitted directly through gap junctions.
**Option C:** This option is incorrect because while both types of synapses transmit signals, the mechanism of transmission is fundamentally different between electrical and chemical synapses.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that electrical synapses are typically found in certain areas of the brain, such as the retina and the olfactory bulb, where rapid signal transmission is crucial for sensory processing.

**Correct Answer:** D. Electrical synapses transmit signals directly through gap junctions, whereas chemical synapses rely on neurotransmitters for signal transmission.