The Blood System 3. Disease Defences 4. Gas Exchange 5. Homeostasis Higher Level 7: Nucleic Acids 1. DNA Structure 2. Transcription 3. Translation 8: Metabolism 1. Metabolism 2. Cell Respiration 3. Photosynthesis 9: Plant Biology 1. Xylem Transport 2. Phloem Transport 3. Plant Growth 4. Plant Reproduction Genetics 1. Meiosis 2.
Inheritance 3. Speciation Animal Physiology 1. Spatial summation means that the effects of impulses received at different places on the neuron add up so that the neuron may fire when such impulses are received simultaneously, even if each impulse on its own would not be sufficient to cause firing. Temporal summation means that the effects of impulses received at the same place can add up if the impulses are received in close temporal succession. Thus, the neuron may fire when multiple impulses are received, even if each impulse on its own would not be sufficient to cause firing.
Key Points Simultaneous impulses may add together from different places on the neuron to reach the threshold of excitation during spatial summation. This happens when the summation of graded potentials originates from one presynaptic neurone or in other words, the signals overlap reaching a postsynaptic neurone.
If a subthreshold EPSP reaches the neurone then no action potential will be generated, however, if multiple subthreshold EPSPs reach the neurone trigger zone close enough together in time then the two subthreshold EPSPs will sum up to cause a suprathreshold EPSP and an action potential will be generated.
This is an example of postsynaptic integration. Jump to: navigation , search. Personal tools Log in.
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