(1) Synthesis, (2) Transport, (3) Spike Propagation, (4) Exocytosis, Receptor Activation, (6) Separation, (7) Reuptake
What is the Sequence of Events at a Synapse?
Amino Acids, Peptides, Acetylcholine (Ach), Monoamines, Purines, & Gases
What are the types of Neurotransmitters & Neuromodulators?
Glutamate & GABA
What are some Amino Acids?
What is an example of a Peptide?
Serotonine, Dopamine, Noradrenaline
What are some Monoamines?
Adenosine & several of its derivatives
What are some Purines?
Nitric Oxide (NO)
What is an example of a Gas?
Not all synapses are chemical, some are electrical: Gap junctions (space between the two neurons, does electrical stimulation instead of chemical, forms when cells come together for action potential)
What is an Electrical Synapse?
It is an intermediate between neurotransmitter & hormone, can have effects on all nearby cells, modulate (change) the effects of neurotransmitters
What is a Neuromodulator?
Dopamine, Serotonine, Noradrenaline
What are some examples of Neuromodulators?
It begins with substances in the diet that can cross the blood-brain barrier (e.g., DOPA), neurotransmitters made in the cell
What is Synthesis?
Some must be transported from the cell body, transported down the axon to the presynaptic terminal
What happens with Transport?
Release occurs through exocytosis (kiss & run? process by which a cell directs secretory vesicles out of the cell membrane)-everything comes together at the end, where vesicles fuse to the cell membrane & release the neurotransmitters, triggered by Ca++ entry-no Ca++ entry=no release, more than one transmitter can be released from each neuron, diffusion of the transmitter occurs across the synapse
What happens with Release & Diffusion?
Most neurons release at least two neurotransmitters, each neuron releases the same neurotransmitters from all axon terminals, the release of multiple transmitters makes the message more variable and complex
What happens with Release?
Each neuron releases the same neurotransmitters from all axon terminals
What is Dale's Principle?
They are used for fast events (i.e., visual stimulation, touch, or muscle movements), immediately open gates for ions, ex: Glutamate AMPA (Na+), GABA A (Cl-), trigger fast EPSPs or IPSPs, can also be voltage dependent (ex: Glu NMDA: AND gate)
What are Ionotropic Receptors?
Initiate a cascade of metabolic events that result in opening or closing of ion channels, changes in protein production, or gene activation, uses G-protein and second messenger systems: e.g., Adenylate, cyclase, cAMP, Protein kinase, ionic channel
What are Metabotropic Receptors?
The same neurotransmitter can have ionotropic and metabotropic receptors and they can have opposite effects. Moreover, the same synapse can have both types of receptors.
Can the same synapse and the same neurotransmitter have both Ionotropic & Metabotropic Receptors?
Glutamate: AMPA, NMDA, Metabotropic; GABA: A and B
What are the main Receptors?
Breaking down a neurotransmitter with an enzyme, ex: Acetylcholine (acetylcholine-esterase)
What is Inactivation?
Neurotransmitters are taken back up by the presynaptic cell using specialized proteins, ex: serotonin, dopamine; nothing to do with a refractory period, steps: (1) Protein channels close in the postsynaptic terminal after it has been stimulated, (2) leftover neurotransmitters in the cleft, (3) Neurotransmitters are specialized molecules/proteins open on the presynaptic terminal allowing the reuptake of the leftover neurotransmitters
What happens with Reuptake?
Out of the synaptic cleft
Where does Diffusion happen?
Synaptic Depression: depletion of a neurotransmitter, negative feedback from presynaptic autoreceptors, positive or negative feedback from heteroreceptors on axoaxonic synapses (ex: endorphines on substance P)
Regulation of Transmission
Agonist, Antagonist, Affinity, Efficacy, Reuptake, Inactivation
What are the ways that drugs affect synapses?
It is a drug that mimics or increases the effects of a neurotransmitter by binding the same receptor as the endogenous neurotransmitter (Morphine)
What does an Agonist do?
It is a drug that blocks or takes away from the effects of a neurotransmitter (Ketamine)
What does an Antagonist do?
The ability of a drug to bind a receptor
What is Affinity?
The degree to which the drug activates the receptor once bound (Valium)
What is Efficacy?
What is Reuptake?
What is Inactivation?