ABSTRACT
The functional unit of the nervous system is the neuron (Figure 2.1). All nerve impulses, or action potentials, originate in neurons. They travel along the neuron’s extended cytoplasm, called the axon, to the point inside or outside the brain where an impulse is required to initiate one of many possible actions – for example, triggering another action potential within a second neuron, or a muscle contraction, or possibly a glandular secretion. Action potentials make things happen and therefore the cell generating the impulse has some control over that action. Strong or rapidly repeated impulses along a neuron result in powerful activities, such as muscle contraction.
