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Postsynaptic neuron

1. Presynaptic neuron. Nerve impulse. 2. Ca 2+. 2. Ca 2+. Voltage-gated Ca 2+ channel. Synaptic end bulb. Cytoplasm. Synaptic vesicles. Synaptic cleft. Ca 2+. Neurotransmitter. Na +. 3. 4. Neurotransmitter receptor. Ligand-gated channel open. 5. Ligand-gated channel closed.

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Postsynaptic neuron

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  1. 1 Presynaptic neuron Nerve impulse 2 Ca2+ 2 Ca2+ Voltage-gated Ca2+ channel Synaptic end bulb Cytoplasm Synaptic vesicles Synaptic cleft Ca2+ Neurotransmitter Na+ 3 4 Neurotransmitter receptor Ligand-gated channel open 5 Ligand-gated channel closed Postsynaptic neuron Postsynaptic potential Nerve impulse 7 6

  2. Postsynaptic Potentials • A neurotransmitter causes either an excitatory or an inhibitory graded potential: • Excitatory postsynaptic potential (EPSP) causes a depolarization of the postsynaptic cell, bringing it closer to threshold. • Inhibitory postsynaptic potential (IPSP) hyperpolarizes the postsynaptic cell taking it farther from threshold.

  3. Postsynaptic Potentials • Spatial summation occurs when postsynaptic potentials arrive near the same location. • Temporal summation occurs when postsynaptic potentials arrive close to the same time.

  4. Presynaptic neuron 3 Cell body Dendrites Presynaptic neuron 4 Presynaptic neuron 2 Axon Axon terminal Presynaptic neuron 1 Presynaptic neuron 5 EPSP Inhibitory neurotransmitter IPSP IPSP EPSP EPSP Excitatory neurotransmitter Trigger zone (net summation of EPSPs and IPSPs determines whether an action potential is generated here) Postsynaptic neuron

  5. Neurotransmitter Clearance • Removal is accomplished by diffusion out of the synaptic cleft, enzymatic degradation, and re-uptake by cells. • Example: acetylcholine - acetylcholinesterase breaks down acetylcholine in the synaptic cleft.

  6. Myasthenia gravis Organophosphorus poisoning

  7. Myasthenia gravis

  8. Organophosphate poisoning

  9. Neurotransmitters

  10. Neuropeptides: • Example: Enkephalines, endorphins, dynorphins, substance P

  11. Neural Circuits • Neurons process information when changes occur at the trigger zone through spatial and temporal summation of IPSPs & EPSPs. • An “average” neuron receives 10,000 synaptic inputs.

  12. Neural Circuits • Integration is the process accomplished by the post-synaptic neuron when it combines all excitatory and inhibitory inputs and responds accordingly.

  13. Neural Circuits • Types of circuits include diverging, converging, reverberating, and parallel after-discharge.

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