General Principles Of Pharmacology/Pharmacodynamics
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Definitions
•Agonist:A drug which causes a physiological effect.
•Antagonist: A drug which blocks the response produced by an agonist.
•Full agonist: An agonist which produces a maximal response by occupying all or a fraction of receptors.
•Partial agonist: An agonist which produces less than a maximal response even when it occupies all of the receptors.
•Spare receptors: This term refers to the observation of a maximal tissue response when only a fraction of the total number of receptors are occupied.
•EC50: The concentration of an agonist that produces half-maximal effect.
•IC50: The concentration of an antagonist that produces half-maximal inhibition
"As the study of the biochemical and physiological effects of drugs and their mechanisms of action."
What does this mean, why is it important, what are its implications and what background knowledge do we need to understand it?
These are the questions that will be addressed in this section.
The target areas, where the drugs exert their effect, of the drugs we are focusing on is the brain, the study of its anatomy and
physiology falls within the realm of neuroscience. However, these drugs are referred to as psychoactive not neuroactive
substances, we are interested in, not only the anatomical structures and physiology related to drug action, but also to their
associated behaviors and mental states.
Some characterize the brain as a communication grid, with neurons receiving information from the environment and from other
neurons information is encoded within the nervous system. As mentioned above, the task of the mind is to form a meaningful
representation of our environment and store it in our memory. We must be able to retrieve relevant memories in specific
situations and make appropriate responses. In section we address the neural mechanisms associated with this task. The brain does
this by associating patterns of neural activity with certain environmental and internal states, further these patterns of
activation are linked to patterns that represent appropriate response to the environmental or internal state. This is
accomplished through the formation of neural networks, consisting of various numbers of interconnected neurons that become
activated together. Each neuron within the network encodes or detects a minute feature of the environment and "fires" when that
feature is sensed. Groups of neurons, by combining their encoded features are able to represent objects that share their features
and larger groups come to represent entire situations. These groups of neurons, based upon our experience or reinforcement
history becomes associated with other groups of neurons that represent appropriate or effective responses to these situations,
this is called learning.
Within the nervous system, neural networks are formed by neurons that come to represent an aspect of the environment by
communicating with other neurons. This communication between neurons is an electrochemical process, based upon the generation of
an action potential, an "all or none" process within a neuron, that in turn, releases chemical messengers called
neurotransmitters, that pass information among the neurons that make up the network.
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