Lectures3+4-Chapter_2-BiologicalFoundations

neurotransmitters and their receptors each type of

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Unformatted text preview: refore whether the postsynaptic neuron will fire or not 51 summary!! Neurotransmitters and their Receptors Each type of neurotransmitter has a high binding specificity for certain kinds of receptors Neurotransmitter receptors are either ion channels themselves, that gate “open” when the neurotransmitter binds to them (causing direct membrane potential changes), or molecules that make biochemical changes inside the cell that indirectly change the membrane potential 52 53 The synaptic potential This is a small change in the membrane potential caused by neurotransmitter binding to specialized receptors that then allows a momentary flux of ions into and out of the neuron. Because this flux of ions is very brief, these receptors themselves usually cannot generate action potentials unless a large enough number of them are opened on nearby dendrites within the same, short period of time 54 Two Basic Types of Synaptic Potentials GABA is usually hyperpolarizing because its main receptor is a GABAgated Cl- channel (Cl-, an anion, has a lower concentration inside than outside the neuron, maintained by an ion pump). Glutamate is the most Makes the neuron MORE common excitatory likely to fire transmitter in the nervous system (its main receptor is a glutamate-gated Na+ channel). Acetylcholine is a second example. Makes the neuron LESS likely to fire -aminobutyric acid (GABA) is the most common inhibitory transmitter in the nervous system. A second example is glycine. Integration of electrical signals by neurons A neuron has to integrate the hundreds of depolarizing and hyperpolarizing signals received from other neurons onto its dendrites. This is done in a region of membrane at the junction between the soma and axon called the axon hillock. If the net signal in the dendrites is a depolarization that is strong enough to cause the membrane potential of the neuron to reach threshold, then voltage-dependent channels in the axon hillock will open, and the neuron will fire an action potential and release trans...
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This document was uploaded on 02/16/2014.

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