However, the law of mass action implies that all pharmacological effects are concentration Keywords: dose–response relationship, drug‐related adverse effects, Although the exact shape of the function can vary (see Figure 1 8), it is its. In physics, action is an attribute of the dynamics of a physical system from which the equations . which takes a function of time and (for fields) space as input and returns a .. Expanded to first order, the difference between the actions integrals for the . A free particle (mass m and velocity v) in Euclidean space moves in a. And the presentation of simple alternatives is one of the chief functions of the of the time of Americans is devoted to the products of the mass media. But this rather intellectualized, rather remote connection with organized social action is.
This explains the so-called receptor reserve phenomenon i.
Action (physics) - Wikipedia
More precisely, receptor reserve refers to a phenomenon whereby stimulation of only a fraction of the whole receptor population apparently elicits the maximal effect achievable in a particular tissue. The simplest interpretation of receptor reserve is that it is a model that states there are excess receptors on the cell surface than what is necessary for full effect. Taking a more sophisticated approach, receptor reserve is an integrative measure of the response-inducing capacity of an agonist in some receptor models it is termed intrinsic efficacy or intrinsic activity and of the signal amplification capacity of the corresponding receptor and its downstream signaling pathways.
Thus, the existence and magnitude of receptor reserve depends on the agonist efficacytissue signal amplification ability and measured effect pathways activated to cause signal amplification.
However, there is no biological or physical theory which relates effects to the log of concentration. It is just convenient for graphing purposes.
The mass action equation in pharmacology
The graph shown represents the conc-response for two hypothetical receptor agonists, plotted in a semi-log fashion. The curve toward the left represents a higher potency potency arrow does not indicate direction of increase since lower concentrations are needed for a given response.
The effect increases as a function of concentration. Unfortunately, there are many factors that make achieving this goal at best difficult, and at worst, impossible. For example, events that affect the equilibrium of the drug at the receptor limited diffusion on a macro or micro scale, metabolism, entrapment, etc. Even more importantly, the production of a stimulus often does not have a one-to-one correspondence to the measured response.
The mass action equation in pharmacology
The response caused by an activated receptor can involve a variety of different mechanisms see cartoon in Figure 1. Some receptors directly effect the response of interest e. Even in this case, other factors including allosteric modulators, cofactors, etc.
In other cases, like a tyrosine kinase B. In the case of G protein coupled receptors C. Theories of Drug-Receptor Interaction There have been several major theories that have been proposed to provide a theoretical basis for understanding, modeling, and thereby predicting, drug response.The Role of Insulin in the Human Body
Three of the most widely known of these schemes are described as follows: All of these theories have specific strengths and appeal, and all have significant failings.
In general, rate theory is now considered to be the one of least utility.
As molecular tools begin to provide ways of studying several sequential molecular events, operational theory or direct multi-step models can certainly be applied. Law of Mass Action Although there are a plethora of complexities that arise, it is true that the large majority of experiments [especially those using radioreceptor methods radioligand binding methods ] are based on very simple application of the law of mass action. In the case of a drug ligand interacting with a homogeneous population of receptors, this relationship can be expressed: Binding occurs when ligand and receptor collide due to diffusion in the correct orientation and with enough energy.