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Understanding Synaptic Transmission: Chemical vs. Electrical Synapses and Action Potentials

This overview examines synaptic transmission, focusing on the two primary types of synapses: chemical and electrical. Chemical synapses utilize neurotransmitter-receptor interactions, while electrical synapses involve direct contact between the presynaptic and postsynaptic cells, allowing for faster transmission of electrical signals. The resting membrane potential, determined by the balance of Na+ and K+ ions, plays a crucial role in action potentials. Understanding the all-or-nothing principle and the mechanisms behind depolarization and repolarization is essential for grasping neural communication.

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Understanding Synaptic Transmission: Chemical vs. Electrical Synapses and Action Potentials

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  1. Nervous System II SBI4U

  2. Synaptic Transmission

  3. Synaptic Transmission • 2 types of synapses: Chemical & Electrical • Neurotransmitter-Receptor vs. Gap junctions

  4. Electrical signals & electical synapse • Plasma membrane of presynaptic and postsynaptic cell are in direct contact. • Current flows directly (unbroken transmission of electrical signal) • Faster neural transmission than chemical synapse

  5. Resting membrane potential Membrane potential: imbalance between charges outside and inside the membrane that causes an electrical (electrical difference between Na+ and K+) - 3 Na+ for every 2K+ ions pumped in(Na+/K+ active transport pump) - An unstimulated neuron has a resting membrane potential where the voltage difference in the nerve cell is – 70mV

  6. Action potential • Membrane potential changes during an electrical impulse. • All or nothing principle : frequency of AP not magnitude (a greater stimulus  faster AP not bigger)

  7. Action potential in Chemical synapse

  8. Activity-Questions • What is all-or-none response? • What is the difference between chemical and electrical synapse? • Which area of the graph indicates the opening of Na+ channels and their diffusion into nerve cells? And when does repolarisation occur ?explain

  9. Pg.529 Q1-3

  10. Answers • 1. A certain threshold stimulus is required to trigger an AP along a nerve. However, once the threshold has been reached further increase in stimulus will not increase nerve response. It is all-or-none response. A nerve or muscle fibre responds completely to a stimulus or it does not at all. • 2- Electrical transmission faster, diminish as it travels, and uses excitation energy to push elecrons. • Chemical: slower, impulse remain strong, uses cellular energy to generate current

  11. 3. During depolarization of the membrane . As it is depolarized the sodium ions rush into the cell causing the membrane potential to increase. Repolarisation occurs when K+ ions diffuses out of the axon. This diffusion lowers the membrane potential of the nerve cell.

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