Which of the following statements about dendrites is true?

The statement that dendrites receive impulses from other neurons is true because dendrites are specialized structures on neurons that are primarily responsible for receiving synaptic signals. They are typically branch-like extensions that increase the surface area of the neuron, allowing it to connect with and receive information from many other neurons. When a neuron is activated, neurotransmitters released from the axon terminals of neighboring neurons bind to receptors on the dendrites, leading to a change in the electrical state of the neuron that can trigger an action potential if the signal is strong enough. This process is fundamental for neural communication and contributes significantly to the brain's functioning, learning, and memory.

The other statements do not accurately describe the role of dendrites. While it's true that they play a critical role in communication, they do not send impulses (as axons do) nor are they classified as output fibers. Additionally, while dendrites are important structures within neurons, they are not the basic building blocks of the brain; instead, neurons, along with glial cells, make up the fundamental units of brain structure and function.