Across the Membrane Flashcards
In the case of a neurotransmitter, what are the three different processes can occur after the NT is released into the synaptic cleft and binds to a receptor (either pre- or post-synaptic receptor)?
Diffusion, Enzyme degradation, Reuptake
the neurotransmitter detaches from receptor, drifting out of the synaptic cleft, here it becomes absorbed by glial cells.
diffusion
enzymes break it down. Usually, astrocytes absorb the excess neurotransmitters and pass them on to enzymes or pump them directly into the presynaptic neuron.
Enzyme degradation
re-absorption of a neurotransmitter into the neuron. Transporters, or membrane transport proteins, pump neurotransmitters from the synaptic cleft back into axon terminals (the presynaptic neuron) where they are stored and reused.
reuptake
If a drug can initiate a cellular response like that caused by the normal endogenous neurotransmitter it is
agonist action
If a drug can initiate a cellular response that is like the normal endogenous NT, but lower amplitude it is
partial agonist
If a drug can block access to the binding site
antagonist action
If a drug can initiate a cellular response opposite to that caused by the normal endogenous neurotransmitter it is
inverse agonist action
If the receptor is near the normal endogenous neurotransmitter binding site, and the drug can facilitate the binding of the normal endogenous neurotransmitter to its normal receptor
allosteric action
Sometimes, the binding of a substance has a helper function. This is called
allosteric action
If administration of a drug reduces the effect of the agonist
antagonist
blocks binding, but does not produce an effect on its own
antagonist
Some antagonists are competitive
more agonist can overcome it
Some antagonists are non-competitive
more agonist cannot overcome it and it binds irreversibly to the receptor
Name the four sites for drug action
Ion Channel Receptors
G-Protein Coupled Receptors
Enzymes
Transporter Proteins
Describe how drug effects occur at a neuron level.
Effects are caused by an interaction with receptor sites on proteins (on the neuron). Drug binding causes a change in the function of these proteins in a characteristic response.
Fast neurotransmitters (milliseconds) that transmit things like vision or hearing
ionotropic receptors
bind to a receptor to facilitate the action of the neurotransmitter
Allosteric agonists
G-protein coupled receptors are also called
metabotropic receptors
The neurotransmitter binds directly to ligand-gated ion channel in the postsynaptic membrane, which closes or opens a channel gate and alters the flow of specific ions into a gated cell.
The direct pathway
G-protein opens or closes ion channels in one of two ways
Directly
Indirectly through secondary messengers (e.g., cAMP)
The extracellular signal molecule binds with the G-protein receptor on the cell surface and activates phospholipase C, which is located on the plasma membrane. The lipase hydrolyzes phosphatidylinositol 4,5-bisphosphate into two second messengers: inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 binds with the IP3 receptor in the membrane of the smooth endoplasmic reticulum and mitochondria to open Ca++ channels. DAG helps activate protein kinase C, which phosphorylates many other proteins, changing their catalytic activities, leading to cellular responses and changes in the ion channel.
INDIRECT PHOSPHATIDYLINOSITOL PATHWAY:
Adenylyl cyclase is a 12-transmembrane glycoprotein that catalyzes ATP to form cAMP. The cAMP produced is a second messenger in cellular metabolism and is an allosteric activator of protein kinase A. Protein kinase A is an important enzyme in cell metabolism due to its ability to regulate cell metabolism by phosphorylating specific committed enzymes in the metabolic pathway
INDIRECT cAMP PATHWAY
What breaks down breaks down monoamines?
monoamine oxidase
What breaks down breaks down acetylcholine?
acetylcholinesterase
The characteristic of a receptor that describes its exclusivity for a particular substance is called its
receptor binding specificity
a substance are molecularly identical, but geometrically different
isomer
substances that are mirror images of each other
optical isomer
A mix of optical isomers is called
enantiomers
levo
left
dextro
right
sinister
left
rectus
right
the immediate response from the binding
The acute effect of a drug at its receptor
changes in the number of receptors or the change in the sensitivity of existing receptors to binding with the exposed substance
chronic effects due to a drug
An increase in the number of receptors is called xxxxx and occurs most often in response to a xxxxx
upregulation, non-competitive antagonist
xxxxxx or a decrease in receptors occurs most often in response to long-term exposure to a
Downregulation, agonist
, long-term exposure to an agonist can cause the existing receptors to
lose sensitivity for the endogenous NT
and long-term exposition to an antagonist can cause receptors to
become more sensitive to the endogenous NT
