Physiology of a Neuron from Dendrite to synaptic transmission



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Physiology of a Neuron from Dendrite to synaptic transmission


SECTION ONE





Function of Dendrites in Stimulating Neurons

  • Dendrites spaced in all directions from neuronal soma.

  • Dendrites transmit signals after the opening of LGC’s

  • LGC (Ligand-gated channels): these open when a ligand (neurotransmitter) binds to them. They do not need an action potential to open them. ‏


Types of Ligand Gated Channels (LGC’s)‏

Many human diseases are associated with dysfunction of particular types of ion channels.

Some Amino Acids have positive charges which repel ions with a positive charge. Some AA’s have negative charges. Amino acids on LGC’s therefore control ion selectivity (what ions may pass). Sodium (Na+) has its own LGC. So does potassium (K+) and Cloride (Cl-).

What would happen to the resting membrane potential if these channels opened?





  • The Excitatory Postsynaptic Potential (EPSP)‏

    • Postsynaptic refers to the dendrite of the neuron receiving the signal.

    • The neurotransmitter binds to its LCG, which opens a Na+ ionophore. Na+ ions then rush to the inside of the cell membrane. They take their positive charge with them, so the inside of the cell membrane is now more positively charged than it was.

    • This increase in voltage above the normal resting potential (to a less negative value) is called the excitatory postsynaptic potential.

    • How many mV do we need to reach threshold? If Resting Membrane Potential is minus 74, we need to get above zero to start an action potential.




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