The Cellular Process in Which a Signal Is Conveyed to Trigger a Change in the Activity or State of a Cell. Signal Transduction Begins with Reception of a Signal (e.g. a Ligand Binding to a Receptor or Receptor Activation by a Stimulus Such As Light) or For Signal Transduction in the Absence of Ligand Signal Withdrawal or the Activity of a Constitutively Active Receptor. Signal Transduction Ends with Regulation of a Downstream Cellular Process E.g. Regulation of Transcription or Regulation of a Metabolic Process. Signal Transduction Covers Signaling From Receptors Located On the Surface of the Cell and Signaling Via Molecules Located Within the Cell. For Signaling Between Cells Signal Transduction Is Restricted to Events At and Within the Receiving Cell.
The Chemical Reactions and Pathways Including Anabolism and Catabolism by Which Living Organisms Transform Chemical Substances. Metabolic Processes Typically Transform Small Molecules But Also Include Macromolecular Processes Such As DNA Repair and Replication and Protein Synthesis and Degradation.
A Neuron Projection That Has a Short Tapering Often Branched Morphology Receives and Integrates Signals From Other Neurons or From Sensory Stimuli and Conducts a Nerve Impulse Towards the Axon or the Cell Body. in Most Neurons the Impulse Is Conveyed From Dendrites to Axon Via the Cell Body But in Some Types of Unipolar Neuron the Impulse Does Not Travel Via the Cell Body.