Biology » The Nervous System » How Neurons Communicate

Summarizing How Neurons Communicate

Summary

Neurons have charged membranes because there are different concentrations of ions inside and outside of the cell. Voltage-gated ion channels control the movement of ions into and out of a neuron. When a neuronal membrane is depolarized to at least the threshold of excitation, an action potential is fired. The action potential is then propagated along a myelinated axon to the axon terminals. In a chemical synapse, the action potential causes release of neurotransmitter molecules into the synaptic cleft.

Through binding to postsynaptic receptors, the neurotransmitter can cause excitatory or inhibitory postsynaptic potentials by depolarizing or hyperpolarizing, respectively, the postsynaptic membrane. In electrical synapses, the action potential is directly communicated to the postsynaptic cell through gap junctions—large channel proteins that connect the pre-and postsynaptic membranes. Synapses are not static structures and can be strengthened and weakened. Two mechanisms of synaptic plasticity are long-term potentiation and long-term depression.

Glossary

action potential

self-propagating momentary change in the electrical potential of a neuron (or muscle) membrane

depolarization

change in the membrane potential to a less negative value

excitatory postsynaptic potential (EPSP)

depolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell

hyperpolarization

change in the membrane potential to a more negative value

inhibitory postsynaptic potential (IPSP)

hyperpolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell

long-term depression (LTD)

prolonged decrease in synaptic coupling between a pre- and postsynaptic cell

long-term potentiation (LTP)

prolonged increase in synaptic coupling between a pre-and postsynaptic cell

membrane potential

difference in electrical potential between the inside and outside of a cell

refractory period

period after an action potential when it is more difficult or impossible for an action potential to be fired; caused by inactivation of sodium channels and activation of additional potassium channels of the membrane

saltatory conduction

“jumping” of an action potential along an axon from one node of Ranvier to the next

summation

process of multiple presynaptic inputs creating EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential

synaptic cleft

space between the presynaptic and postsynaptic membranes

synaptic vesicle

spherical structure that contains a neurotransmitter

threshold of excitation

level of depolarization needed for an action potential to fire

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