All or none response

Quantal dose-response curves based on all-or-none responses. A. Relationship between the dose of phenobarbital and the protection of groups of rats against convulsions. B. Relationship between the dose of phenobarbital and the drug s lethal effects in groups of rats. ED50, effective dose, 50% LD50, lethal dose, 50%. 

Quantal Effect An effect that either happens or does not happen, e.g. death. Synonym all-or-none response. 

For example, the industrial chemical hydrazine not only causes death, as a result of effects on the central nervous system, but also causes dysfunction in the liver, leading to the accumulation of fat. This effect is not related to the lethality, but it shows a clear relationship with dose. The response, that is, fatty liver, is a graded effect rather than an all-or-none response and can be quantitated either as an increase in liver weight (as percent of body weight) or by specific measurement of the triglycerides. Both measurements show a similar dose-effect curve (Fig. 2.2). 

When information is derived from human epidemiological studies, it will normally be incidence of a particular disease or morbidity such as cancer or maybe the appearance of a novel disease, that is, all-or-none responses. 

The occurrence of histamine release is also treated as an all-or-none response to permit log-probit plotting. The delayed depressor response plus tachycardia is judged to have or have not occurred after each single bolus injection of the drugs. The percentage of animals responding at each dose level is then determined and the data handled by the Litchfield-Wilcoxon method. 

Q10 (temperature coefficient) The increase in the rate of a chemical process due to raising the temperature by 10 C. quantal responses Are all-or-none responses, or qualitative responses, e.g. death or survival (in contrast to quantitative responses which are continuous variables). The underlying distribution is the binomial distribution. Log dose-response lines for quantal responses are frequently sigmoidal in shape, and since this is the same form as the integrated frequency distribution curve, the slope of the... 

When the sum of the light stimuli exceeds a certain threshold an all-or-none response is triggered. The PC becomes superimposed by an action potential-like response (67, 68), which is related to the flagella membrane current and was therefore named flagellar current (PC). The PC is due to a massive calcium influx... 

One of the possible causes of the receptor reserve is demonstrated by the all or none response, e.g. in smooth-muscle cells. A single effector unit. Le. a single smooth-muscle cell, either contracts maximally or does not contract at all. This reaction of a single unit is evoked at a certain drug concentration, and thus at a certain RA concentration and at a definite stimulus value. Even if the stimulus is increased no further enhancement of the reaction of the single unit is possible. 

The enormous flexibility and amplification achievable by enzymes involved in a cascade of activation—and which are also sensitive to allosteric regulation—has been the focus of a theoretical analysis by Stadtman and Chock (1977) and Chock and Stadtman (1977). They emphasized the dynamic aspect of the interconversion process, providing for a spectrum of specific activity of modifiable enzymes rather than an all-or-none response. Their analysis is amply borne out by the recent data on glycogen synthase. 

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