Term
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Definition
- a junction between a neuron and another cell (which could be a neuron or another cell type, like a muscle cell)
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Term
| Intercelluar Communcation |
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Definition
- Direct communication through gap junctions
- Gap junctions are composed of membarne protein structures called connexons that link the cytosols of two adjacent cells, allowing ions and small molecules to move between cells
- Communcation via chemical messengers
- secretory cell releases a messenger into the ECF, the messenger binds to receptors on target cells, triggering a response in the target cell
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Term
| Properties of chemical synapses |
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Definition
- pre-synaptic neuron sends signals to post-synaptic cell
- an example of intercellular communication
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Term
| Events of synaptic communication |
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Definition
- Action potential in pre-synaptic cell reaches the synapse
- Voltage-gated calcium channels in teh pre-synaptic cell open
- Calcium comes into the pre-synaptic cell
- Calcium causes vesicles to undergo exocytosis
- Neurotransmitter molecules released into synaptic cleft
- Some neurotransmitter molecules many bind to receptors in the post-synaptic cell
- Neurotransmitte molecules may also be degraded by enzymes
- or brought back into the pre-synaptic cell or
- can be recycled or just diffused out of the synaptic cleft
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Term
| Fast responses of post-synaptic cell |
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Definition
- Ligand-gated ion channels open in response to neurotransmitter binding
- Ions enter or leave post-synaptic cell
- Signaling is fast, but isn't that strong because of lack of amplification
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Term
| Slow responses of post-synaptic cell |
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Definition
- G-protein coupled receptors transmit signal to ion channel, via a g-protein
- The g-protein, or sometimes an activated 2nd messenger, will lead to a conformational change in the channel, to open or close the channel
- A change in the flow of ions will result
- ex: ions will enter or leave post-synaptic cell if channels were opened
- Signaling is slow, but can be quite strong because of amplivication
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Term
| Propagation toward the axon hillock |
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Definition
- Both fast and slow responses affected the flow of ions into or out of the post-synaptic cell
- Ions are always charged
- When charged particles change their distribution across the plasma membrane, Vm changes
- These are graded potential changes
- Changes in Vm are largest at the site of origin, and degraded as they go toward the axon hillock
- this gives a strentgh advantage to synapses closer to the axon hillock
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Term
| Propagation toward the axon hillock synapses - Excitatory |
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Definition
- Excitatory
- depolarize post-synaptic cell (Vm more positive)
- ex: opening Na+ channels - Na+ comes in, deplorizing the cell
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Term
| Propagation toward the axon hillock synapses - Inhibitory |
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Definition
- hyperpolarize post-synaptic cell
- makes the Vm more negative
- ex: opening K+ channels - K+ goes out, hyperpolarizing the cell
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Term
| Post-synaptic neurons as decision makers |
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Definition
- change in membrane potential due to a single pre-synaptic axon exciting a post-synaptic cell is usually not enough to cause the cell to fire an action potential
- action potential is only triggered if Vm (at the axon hillock) reaches threshold
- Most neurons receive synapses from hundreds or thousands of other neurons
- A post-synaptic cell does summation
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Term
| Post-synaptic cell summation |
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Definition
- Signaling from inhibitory synapses makes it less likely to fire an action potential
- Signaling from excitatory synapses makes it more likely to fire
- Waiting for a preponderance of positive (excitatory) evidence, and by receiving excitatory and inhibitory signals from the appropriate pre-synaptic cells, the firing of a post-synaptic neuron can have some meaning
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Term
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Definition
- operate by allowing electrical signals to be transmitted from one neuron to another through gap junctions
- can be excitatory or inhibitory at the same synapses as either a depolarizing or a hyperpolariaing current
- identified in the retina of the eye and certain areas of the cortex
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Term
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Definition
- operate through the release of neurotransmitters that activate signal transduction mechanisms in the target cell
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Term
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Definition
- the first neuron, which transmits signals to the second neuron
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Term
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Definition
- the second neuron, which receives signals from the first neuron (presynaptic neuron)
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Term
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Definition
- the narrow space between the presynaptic and post-synaptic neurons
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Term
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Definition
- store neurotransmitter molecules
- neurotransmitters are synthesized in the cytosol of the axon terminal, where the enzymes for their synthesis are located
- after synthesis, neurotransmitters are actively transported into synaptic vesicles
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Term
| Cytosolic calcium triggers the release of |
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Definition
- neurotransmitter by exocytosis
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Term
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Definition
| site of communication at which activity in the presynaptic neuron causes depolarization of the postasynaptic neuron |
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Term
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Definition
| a change in the membrane potential in a postsynaptic neuron that occurs in response to the binding of neurotransmitters to receptors |
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Term
| Excitatory postsynaptic potential |
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Definition
| a graded depolarization caused by neurotransmitter binding to receptors on the postsynaptic neuron |
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Term
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Definition
| a phenomenon occuring at an axo-axonic synapse such that activity in the presynaptic neuron enhances the release of neurotransmitter from the postsynaptic neuron |
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Term
| inhibitory postsynaptic potential |
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Definition
| a graded hyperpolarization caused by neurotransmitter binding to receptors on the postsynaptic neuron |
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Term
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Definition
| site of communication whereby activity in the presynaptic neuron decreases the likelihood of an action potential occurring in the postsynaptic neuron |
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