neurotransmitters Flashcards
what are neurotransmitters?
chemicals that transmit the signals of neurons
-not all chemicals produced by neurons are neurotransmitters
what does a chemical need to do to be considered as a neurotransmitter?
-Be synthesised and stored (generally in synaptic vesicles) in the presynaptic neuron
-Be released by the presynaptic axon terminal
-Produce responses in the postsynaptic cell,they function at the synapse
state the different structures of a typical synapse
-presynaptic terminal
-mitochondria
-secretory granules
-synaptic cleft
-synaptic vesicles
-active zone
-postsynaptic density
what is the presynaptic terminal?
-the end of the axon that forms the synapse (the conc of mitochondria is greater here)
what does the mitochondria do?
provides energy for the synaptic transmission
what are the secretory granules?
cell organelles which contain chemical (usually neuropeptides) which are released from the axon terminal to activate receptors on surrounding neurons
what is the synaptic cleft?
the area between the presynaptic terminal and postsynaptic regions (the space within a synapse)
what are the synaptic vesicles?
small spheroid cell organelles in which neurotransmitters are packaged
-this protects the neurotransmitters from degradation by surrounding enzymes, the release of neurotransmitters occurs by the fusing of the vesicles with the presynaptic membrane and releasing the contents
what is the active zone?
the part of the presynaptic regions where synaptic vesicles dock and are released
what is the postsynaptic density?
a region of the postsynaptic membrane, full of receptors
what are the chemicals at the presynaptic terminal of a typical synapse?
-neurotransmitters(proteins) and the enzyme (proteins) required for their synthesis
-vesicular transporters
-reuptake transporters
-degradative enzymes
what are vesicular transporters?
proteins which transport the neurotransmitter unto the synaptic vesicles
what are reuptake transporters?
proteins which take or transport the released neurotransmitter back into the presynaptic terminal
what are degradative enzymes?
they break down any free neurotransmitter
what are the chemicals at the postsynaptic region of a typical synapse?
-receptors=the proteins through which the neurotransmitter relays its signals or effects (can be presynaptic swell)
-secondary messengers (biochemical pathways which are initiated following the binding of the neurotransmitter to receptors
how do neurotransmitters function?
-all neurotransmitters(located presynaptically) function by binding to specific proteins
(receptors) which can be located pre or postsynaptically
-these activated receptors then cause a change in the function of the postsynaptic neuron, this can either be:excitation or inhibition of the postsynaptic neuron
what are agonists and antagonists?
agonists=agents(neurotransmitters/drugs) that bind to receptors
atangonists=agents that block receptors and prevent agonists from binding to their specific receptors
how do different classes of pharmacological agents work?
by either being an agonist or antagonist at various receptor systems
what are the two main types of receptors?
-ionotropic receptors
-metabotropic receptors
what are inotropic receptors?
proteins embedded in the cell membrane that form pores or channels for passing different ions e.g Na,Ca,Cl between the inside and outside of the neuron
how do ionotropic receptors work?
-When the agonist binds to these receptors the channels open and allow the movement of these ions into the neuron
-this movement of charge creates electrical currents and change the electrical potential of the inside of the cell-changes its excitability
contrast ionotropic receptors and metabotropic receptors..
-ionotropic receptors mediate fast synaptic neurotransmission, their activation results in the passage of ions whilst metabotropic receptors mediate slow synaptic neurotransmission, their activation leads to intracellular metabolic pathway signalling