BioMedical Admissions Test (BMAT) 2025 – 400 Free Practice Questions to Pass the Exam

The term 'diffusion' in the context of neuron signaling refers to the random movement of molecules from an area of high concentration to an area of low concentration. This process is a fundamental mechanism that allows substances, such as ions or neurotransmitters, to move across membranes and spaces within the neuron and between neurons.

When a neurotransmitter is released into the synaptic cleft, for example, it moves from an area of higher concentration (the synaptic vesicles) to an area of lower concentration (the postsynaptic receptor sites) due to diffusion. This movement is passive and does not require energy, making diffusion a key process in how neuronal communication occurs.

In contrast, the other options describe different mechanisms or processes that are not the definition of diffusion itself. The movement of ions through channels is a specific mechanism involving facilitated diffusion or active transport rather than diffusion in its general sense. The transfer of electrical impulses pertains to action potentials and signal propagation along the neuron, not molecular movement in terms of concentration gradients. Active transport of neurotransmitters involves energy expenditure to move substances against their concentration gradient, which stands in contrast to the passive nature of diffusion.