BIO315H5 Lecture 3: BIO315 – Lecture 3 Study Notes
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A signal induces a response only for as long as the signal persists. This is because responses may be regulated through feedback mechanisms such as positive feedback. The product feeds back to stimulate its own production. In negative feedback, the cell may turn off the response, it doesn"t necessarily have to match the signal. You stimulate frog eggs with increasing concentrations of progesterone and look at the activation of mapk in pooled oocytes as well as individual oocytes. The results highlight which principle of cell signaling? (is it smoothly graded, sigmoidal or all-or-none?) The oocyte is either activated or inactivated by progesterone as a result this is an all-or-none response. Adaptation - prolonged exposure to a stimulus, the response of that cell to that signal decreases with time. This is through negative feedback - negative feedback gives rise to adaptation. Usually cells respond to concentration changes rather than absolute concentrations.
