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In biology, cell signaling (cell signalling in British English) is the process by which a cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all cellular life in prokaryotes and eukaryotes.
The basis for signal transduction is the transformation of a certain stimulus into a biochemical signal. The nature of such stimuli can vary widely, ranging from extracellular cues, such as the presence of EGF, to intracellular events, such as the DNA damage resulting from replicative telomere attrition. [7]
Chemical stimuli, such as odorants, are received by cellular receptors that are often coupled to ion channels responsible for chemotransduction. Such is the case in olfactory cells. [12] Depolarization in these cells result from opening of non-selective cation channels upon binding of the odorant to the specific receptor.
The connection between the external stimulus to the spiking probability is made in two steps: First, a receptor cell model translates the raw external stimulus to neurotransmitter concentration, and then, a spiking neuron model connects neurotransmitter concentration to the firing rate (spiking probability).
Chemoreceptors, or chemosensors, detect certain chemical stimuli and transduce that signal into an electrical action potential. The two primary types of chemoreceptors are: Distance chemoreceptors are integral to receiving stimuli in gases in the olfactory system through both olfactory receptor neurons and neurons in the vomeronasal organ.
The stimulus modality for vision is light; the human eye is able to access only a limited section of the electromagnetic spectrum, between 380 and 760 nanometres. [3] Specific inhibitory responses that take place in the visual cortex help create a visual focus on a specific point rather than the entire surrounding. [4]
They may be locked to an external stimulus such as in the visual [12] and auditory system or be generated intrinsically by the neural circuitry. [ 13 ] Whether neurons use rate coding or temporal coding is a topic of intense debate within the neuroscience community, even though there is no clear definition of what these terms mean.
These communications between cells triggers intracellular signaling cascades, termed signal transduction pathways, that regulate specific cellular functions. Each signal transduction occurs with a primary extracellular messenger that binds to a transmembrane or nuclear receptor, initiating intracellular signals.