Podcast
Questions and Answers
What is the therapeutic index of a drug?
Which of the following statements about drug potency is correct?
What shape does a log dose-response curve typically take when plotted on a graph?
Which receptor type is exemplified by insulin?
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What does downregulation of receptors typically lead to?
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What is the therapeutic window of a drug?
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Which drug is an example of having a high therapeutic index?
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In the context of pharmacology, what defines drug potency?
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Receptors are macromolecules present on the cell surface, cytoplasm, or in the ______ with which the drug binds.
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A drug that can produce pharmacological action after binding to the receptor is called an ______.
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A drug that binds to receptors but is not capable of producing pharmacological action is called an ______.
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A ______ agonist binds to the receptor but produces an effect less than that of a full agonist.
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Inverse agonists have a full affinity towards the receptor but produce an effect ______ to that of an agonist.
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G-protein-coupled receptors are coupled to intracellular effectors through ______.
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Ligand-gated ion channels, also known as ______ receptors, include nicotinic acetylcholine receptors.
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Receptors regulating gene expression are often referred to as ______ receptors.
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Study Notes
Pharmacology 1
- The course is for the Faculty of Dentistry.
- Enzyme-linked receptors:
- An example is the insulin receptor.
- Binding of an agonist to the receptor's extracellular domain triggers dimerization.
- This activates intracellular signaling pathways.
- Leads to a tissue response.
Nuclear Receptors
- Examples include receptors for sex steroids and glucocorticoids.
- Ligands bind to receptors.
- Corepressors and coactivators are involved in the process.
- Transcription target genes are activated.
Receptor Types Summary Table
- Ligand-gated ion channels are located on the membrane and use ion channels as effectors. Direct coupling is used. Examples include nicotinic, GABA, and other receptors. Response time is milliseconds.
- G-protein-coupled receptors are also membrane-bound, using channels or enzymes as effectors and G-proteins (Gs, Gi, Gq, etc.) for coupling. Examples include muscarinic and adrenergic receptors. Response time is seconds.
- Enzymatic receptors are membrane-bound, using enzymes as effectors and direct coupling. Examples include insulin, growth factor, and cytokine receptors. Response time is hours.
- Nuclear receptors are located intracellularly, use DNA as effectors, and employ direct coupling. Examples include steroid, thyroid hormone receptors. Response time is hours.
Receptor Regulation
- Receptors can be upregulated or downregulated.
- Upregulation:
- Prolonged agonist use increases receptor number and sensitivity.
- Sudden antagonist withdrawal can lead to a stronger response to agonists.
- Downregulation:
- Prolonged agonist use decreases receptor number and sensitivity.
- Example: chronic salbutamol use reduces beta-2 adrenoreceptors.
Dose-Response Relationship
- The pharmacological effect varies with the drug's concentration at its site of action. This concentration is determined by the administered dose.
- A dose-response relationship results.
- Dose response curves are typically plotted as a rectangular hyperbola when plotting dose against the percentage response.
- Plotting the dose on a logarithmic scale gives a sigmoid curve.
Therapeutic Index
- It is the ratio of LD50 (median lethal dose) to ED50 (median effective dose).
- Higher the index, the better the safety margin.
- LD50 is the drug dose lethal to 50% of the population.
- ED50 is the drug dose producing the desired effect in 50% of the population.
- A wider index implies better margin of safety.
- Drugs are less likely to cause harmful effects in individuals.
- Penicillin has a high TI compared to digitalis.
Therapeutic Window
- It's the range of concentrations where the drug produces the desired response with minimal toxicity.
Drug Potency
- Potency is measured by the amount of drug needed for a desired response.
- The lower the dose, the higher the potency.
- Morphine is more potent than pethidine (for the same effect) meaning it requires a lower dose.
Drug Efficacy
- Efficacy is the maximum effect a drug can produce.
- Morphine is more efficacious (than aspirin) for pain relief.
Drug Potency vs. Efficacy
- Potency relates to the dose needed for a particular response.
- Efficacy relates to the maximum possible effect that a drug can produce.
- These two concepts are distinct but related aspects of drug action.
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Description
This quiz covers key concepts in Pharmacology 1, focusing on enzyme-linked receptors, nuclear receptors, and various receptor types. It includes details about the mechanisms of action and signaling pathways of receptors vital to the Faculty of Dentistry curriculum. Understanding these receptor types is essential for comprehending drug actions and therapeutic applications.
