Habituation in Spirostomum

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Habituation is a reversible decrement of response of the cellular organisms to repeated stimulations. It is seen in both aneural and neural organisms which shows its importance in the animal survival. The unicellular organisms, Spirostomum also undergo various changes on habituation.


The unicellular organisms, Spirostomum also undergo changes on habituation. Spirostomum are ciliated protozoa and habituation helps in studying behavioral changes in these parallel to habituation. But it is viewed as a process to filter out iterative stimuli with no significant changes. And the easiest way to judge the changes is that as habituation is a homeostatic process it optimizes the Spirostomum's likelihood of judging the importance of the stimulus in a new iterative series or a change in it.
The method to detect the low or high responsiveness to the stimuli is that if we take the initial responsiveness as organism's threshold prior to stimulus occurrence then if it has high initial response it is said to have lower threshold and if low initial response visa versa. In Spirostomum the time course of contraction is very rapid with 4 to 5 mS as the cells contract at a rate in excess of 100 cell lengths sec-1. And as the stimulus strength duration judges the threshold response, Spirostomum is said to have full or no contraction at all. The changes in resting membrane potential do not cause initial contractions while microinjection of calcium buffers induce contractions.
The Spirostomum are habituated to a mechanical shock and cause brief contractions. And as the stimulation is repeated the number of contractions decreases. ...
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