Introduction to Pharmacology: Pharmacodynamics Flashcards
Define pharmacodynamics.
The study of what drugs do to the body.
Define pharmacokinetics.
The study of what the body does to drugs.
What is a drug?
A substance that brings about a change in biological function through its chemical actions.
What are the 3 types of names a drug is given?
- Chemical; 2. Generic; 3. Brand
In general, what is the function of receptors?
To translate the chemical actions of a drug into a physiological effect.
What are the 4 general classifications of receptors?
- Ion Channel; 2. G-Protein Coupled; 3. Enzyme Coupled Receptors; 4. Intracellular
Describe how an ion channel works.
Ion channels are the fastest type of channels, with receptors on or adjacent to the channel. A ligand binds to the receptor, opening the channel, allowing ions to flow across the membrane, changing the polarity of the cell, which leads to other effects.
What type of ligands are common to ion channels?
Ligands are commonly neurotransmitters, such as acetylcholine and GABA.
Describe how G-protein coupled receptors function.
These are the most common receptors. An agonist binds to the receptor, which activates the coupled G-protein. The G-protein is intracellular, and activates second messengers of a signal transduction pathway (cAMP pathway).
What are second messengers?
Signalling molecules that relay the message from the first messenger (the drug binding to a channel) to effectors in the cytoplasm.
What are ligands common to G-protein coupled receptors?
Adrenergic agents, such as epinephrine.
Describe the functioning of receptors coupled to enzymes (tyrosine kinases).
After ligands binds, the receptors dimerize, activating the tyrosine kinase domain. The activated domain phosphorylates tyrosine residues on various signalling proteins, which then may exert their biochemical effect.
What ligands are common to tyrosine kinases?
Generally growth factors, as well as insulin.
Describe how intracellular receptors function.
These are the slowest to exert their effects. Receptors are located in the cytoplasm or on the nucleus (where it is brought by a chaperone). Receptors are often transcription factors that play a role in gene expression.
What kind of ligands bind intracellular receptors?
Ligands include steroid hormones.
What is an agonist?
A substance that has both affinity and intrinsic activity at a receptor. It can be either endogenous or exogenous.
What is an antagonist?
A substance that has affinity, but lacks intrinsic activity at a receptor. They are often referred to as inhibitors or blockers.
What are the types of antagonists?
Reversible and irreversible.
Describe reversible antagonists.
These bind to receptors in a reversible fashion. Increasing levels of the agonist can “outcompete” the reversible antagonist to overcome its effects.
Describe irreversible antagonists.
These bind to the receptor irreversibly, where increasing the levels of an agonist will not overcome its effect. They are often referred to as non-competitive.
What is a partial agonist?
A substance that has affinity, but less than full intrinsic activity at a given receptor.
What is an inverse agonist?
Inverse agonists bind to constitutively active receptors and inactivate them.
How is an inverse agonist different from an antagonist?
Unlike antagonists, an inverse agonist does not have to have an agonist present to exert an effect.
