Final answer:
Spatial summation of graded potentials occurs when multiple graded potentials at different locations on a neuron add together to reach the threshold for an action potential. It allows the neuron to integrate and process multiple inputs to generate an appropriate response.
Step-by-step explanation:
Spatial summation of graded potentials occurs when multiple graded potentials at different locations on a neuron add together to reach the threshold for an action potential. It involves the combination of signals from separate presynaptic elements that initiate an action potential. This summation can happen across the neuronal cell membrane or over a certain amount of time. Spatial summation is important because it allows the neuron to integrate and process multiple inputs to generate an appropriate response.
For example, if the neuron receives two sub-threshold graded potentials from two different synapses, individually they may not be strong enough to trigger an action potential. However, if these graded potentials occur in close proximity on the neuron, their signals can summate and reach the threshold for an action potential. This allows the neuron to respond to the combined input from multiple sources.
In contrast, temporal summation occurs when multiple graded potentials from the same location on a neuron arrive in rapid succession, resulting in a strong signal from one input. Both spatial and temporal summation can occur together to further enhance the generation of action potentials and the transmission of signals in the nervous system.