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Understanding Neuronal Communication: Synapses, Potentials, and Neurotransmitters

This chapter explores the intricate mechanisms of neuronal communication, emphasizing electrical and chemical synapses. It details how neurotransmitters are synthesized and released from presynaptic neurons and how they affect postsynaptic potentials, including excitatory and inhibitory responses. The concepts of temporal and spatial summation in generating post-synaptic potentials are examined, as well as the modulation of synaptic transmission through various receptor and signaling pathways. Overall, this section provides insights into the foundational processes that underpin brain function.

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Understanding Neuronal Communication: Synapses, Potentials, and Neurotransmitters

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  1. Chapter 48.4 • Jacob Parker, James Pittman Phillips 

  2. Neurons communicating with other cells at synapses • Electrical synapses contain gap junctions which allow current to flow from one neuron to the other. • Majority of synapses are chemical synapses which involve release of neurotransmitter by postsynaptic neuron. • At each terminal, presynaptic neuron synthesizes neurotransmitter and packages it with many compartments called synaptic vesicles. • Neurotransmitter diffuses across synaptic clef, narrow gap that separate presynaptic from postsynaptic cell.

  3. Chemical Synapse 3

  4. Generation of Postsynaptic Potentials • These depolarizations bring membrane potential toward threshold, called excitatory postsynaptic potentials. • Hyperpolarizations produced this way are called inhibitory postsynaptic potentials because they move membrane potential farther from threshold. • Result is generally a postsynaptic potential, a change in membrane potential of postsynaptic cell.

  5. Summation of Postsynaptic Potentials • Unlike actions potentials, post synaptic potentials are graded; magnitude varies with the amount of neurotransmitter released by presynaptic neuron. • Some occasions, two EPSPs occur at single synapse which is an effect called temporal summation. • EPSP’s produced by different synapses on same postsynaptic neuron can also create an effect called spatial summation. • Through both spatial and temporal summation, several EPSP’s depolarize the membrane to the threshold.

  6. Modulated Synaptic Transmission • There are also synapses in which receptor for the neurotransmitter is not part of an ion channel. • Variety of signal transduction pathways play role in modulating synaptic transmission.

  7. Major Neurotransmitters 7

  8. The Amazing Brain • Nerve cells use nerve impulses, also called action potential, to develop the axon at the point where it exits from the nerve cell body. • When it reaches the axon terminal, the action potential ceases. It has done the job though because when it reaches the terminal, it triggers an entirely different process.

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