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Effects of Excitatory and Inhibitory Potentials on Action Potentials

Effects of Excitatory and Inhibitory Potentials on Action Potentials. Overview of A Neuron. Found in brain, spinal cord and nervous system Electrically excitable Communicate via electrical and chemical synapses Made up of a soma (cell body), dendritic tree and an axon. Axon Properties.

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Effects of Excitatory and Inhibitory Potentials on Action Potentials

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  1. Effects of Excitatory and Inhibitory Potentials on Action Potentials

  2. Overview of A Neuron • Found in brain, spinal cord and nervous system • Electrically excitable • Communicate via electrical and chemical synapses • Made up of a soma (cell body), dendritic tree and an axon

  3. Axon Properties • Where action potential is propagated • Contains voltage gated sodium and potassium channels • Resting membrane potential: ~ -65 mV

  4. Action Potential • Occurs when membrane potential exceeds the threshold potential • Occurs when Na+ channels are activated (inflow of Na+) • Causes positive slope of action potential • K+ channels open slightly later (outflow of K+) • Causes downward slope of action potential

  5. Transmission of Action Potential Across Synapse • Pre-synaptic cell action potential releases Ca2+ in the axon terminal • Axon terminal releases vesicles filled with neurotransmitters • Inhibit or help create an action potential • Excitatory Neurotransmitters: • Acetylcholine • glutamate • Inhibitory Neurotransmitters: • GABA • glycine • http://thebrain.mcgill.ca/flash/i/i_01/i_01_m/i_01_m_ana/i_01_m_ana.html#2

  6. Excitatory Post Synaptic Potentials (EPSP) Creates positive synaptic potential Positive charged ions flow in Allows Na+ into cell Easier for Action Potential to fire Inhibitory Post Synaptic Potentials (IPSP) Decreases the potential of the membrane Increases permeability of K+ K+ flows out of cell Decreases the chances of an action potential Post Synaptic Potentials

  7. Temporal Summation One neuron acting on another Potential starts before the previous one ends Amplitudes of potentials summate to create larger potential Spatial Summation Multiple cells provide input Input is received in different areas Input is summated to create a larger potential Ways to Achieve Action Potential

  8. Observations • Increasing the intensity does not increase the size of the action potential • Action potential is “all or none” response • Potentials can summate to elicit or inhibit an action potential • Must reach a specific threshold potential to create and action potential that will be propagated

  9. Conclusion • Many different ways to elicit an action potential or to inhibit one • Temporal and Spatial Summation allow for greater complexity in neural networks • This allows for greater complexity in organisms • neuron can communicate with multiple neurons > greater efficiency.

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