S1: Introduction to Receptors Flashcards
What is pharmacodynamics?
What the drug does to the body and its mechanism of action
What is pharmacokinetic?
What the body does to the drug, how it is absorbed, distributes, metabolised and excreted
What is a drug?
A drug is any chemical that has a biological effect
Name the 3 characteristics of drugs
- Drugs have a variety of effects/tissue selectivity
- Chemical sensitivity
- Drugs are very potent (high affinity and efficacy)
Explain the chemical sensitivity of drugs
Small changes in structure can cause huge changes in bio activity
Example is that the enantiomer (+) for adrenaline produces about 100x greater biological effect the (-) enantiomer
Explain the high potency of drugs
Drugs act in low concentrations
This is because receptors are able to amplify biological responses
What is a receptor?
A receptor is a target molecule which physiological mediator (e.g. neurotransmitter) and ‘given’ drugs bind to, to produce a cellular response
Name 3 general properties of receptors
- They are expressed in different tissues which is why a drug can have effects on different tissue
- They are highly selective targets which only specific structures bind to
- They amplify signals, only small number of drug/receptor interactions needed to initiate significant biological effects
In basic terms, what happens when a drug binds to a receptor (generally)
When the drug molecule binds, it will activate the receptor which causes a conformational change which may change a cellular process
List the 4 types of receptors
Receptors
Enzymes
Carrier molecules
Ion channels
Definition of an agonist
A drug which binds to a receptor to produce a biological cellular response
Definition of a antagonist
A drug which binds to a receptor but does not produce a biological effect
They often bind to receptors to prevent agonists producing effects
What are the 2 steps in drug action and what are they governed by?
- Occupation which is a drug binding to receptor (governed by affinity)
- Activation which is producing a response (governed by efficacy)
What is affinity?
The degree to which a substance tends to combine with another
What is efficacy?
The ability to produce a desired or intended result
Does an agonist have affinity and efficacy?
Yes
An agonist will have affinity and occupy it to form a complex between receptor and agonist and then it will activate the receptor due to its efficacy producing a biological response
Does a antagonist have affinity and efficacy?
No
An antagonist has affinity so will occupy it but it will not activate it due to no efficacy
Which are the two main ways of classifying drugs?
- According to their clinical use
2. According to target receptor
How are receptors classified?
They are classified according to agonist and antagonists that act on the receptors
What are the two types of adrenoreceptors?
Alpha and Beta
They are distinguished by the agonist and antagonist that act on them
Why are some adrenoreceptors classified as alpha-adrenoreceptors
For some adrenoreceptors where noradrenaline is more potent than adrenaline which is more potent then isoprenaline
Why are some adrenoreceptors classified as beta-adrenoreceptors
Isoprenaline is more potent than adrenaline which is more potent than noradrenaline
What happens to alpha-adrenoreceptors in the blood vessels when stimulated?
Increase blood vessel constriction
What happens to beta-adrenoreceptors in the heart when stimulated?
Stimulate heart rate
