Chapter 8b Neurons Cellular and Network Properties 2013 Pearson Education Inc Cell to Cell Neurons Communicate at Synapses Electrical synapses pass electrical signals through gap Chemical synapses use neurotransmitters that cross junctions synaptic clefts 2013 Pearson Education Inc Cell to Cell Neurocrine Receptors Ionotropic receptors Receptor channels Mediate rapid responses Alter ion flow across membranes Metabotropic receptors G protein mediated receptors Mediate slower responses Some open or close ion channels 2013 Pearson Education Inc Cell to Cell Neurocrines Seven classes by structure Acetylcholine Amines Amino acids Peptides Purines Gases Lipids 2013 Pearson Education Inc Receptors Cholinergic receptors Nicotinic on skeletal muscle in PNS and CNS Monovalent cation channels Na and K Muscarinic in CNS and PNS G protein coupled receptors Adrenergic Receptors and G protein coupled receptors 2013 Pearson Education Inc Derived from single amino acid Tyrosine Dopamine Norepinephrine is secreted by noradrenergic neurons Epinephrine Amines Tryptophan Serotonin Histadine Histamine 2013 Pearson Education Inc Amino Acids Glutamate Excitatory CNS Aspartate Excitatory brain GABA Inhibitory brain Glycine Inhibitory spinal cord May also be excitatory 2013 Pearson Education Inc Other Neurotransmitters Peptides Substance P and opioid peptides Purines AMP and ATP Gases NO CO and H2S Lipids Eicosanoids 2013 Pearson Education Inc Table 8 4 Major Neurocrines Figure 8 18 A chemical synapse Schwann cell Axon terminal Mitochondrion Vesicles with neurotransmitter Synaptic cleft Muscle fiber Figure 8 19a ESSENTIALS Synaptic Communication Neurotransmitter Release Action potential arrives at axon terminal Docking protein Ca2 Postsynaptic cell Voltage gated Ca2 channel Cell response Synaptic vesicle with neurotransmitter molecules Synaptic cleft Receptor An action potential depolarizes the axon terminal The depolarization opens voltage gated Ca2 channels and Ca2 enters the cell Calcium entry triggers exocytosis of synaptic vesicle contents Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell Neurotransmitter binding initiates a response in the postsynaptic cell Figure 8 19a ESSENTIALS Synaptic Communication Slide 1 An action potential depolarizes the axon terminal Synaptic vesicle with neurotransmitter molecules Synaptic cleft Action potential arrives at axon terminal Postsynaptic cell 2013 Pearson Education Inc Figure 8 19a ESSENTIALS Synaptic Communication Slide 2 Action potential arrives at axon terminal Synaptic vesicle with neurotransmitter molecules An action potential depolarizes the axon terminal The depolarization opens voltage gated Ca2 channels and Ca2 enters the cell Ca2 Synaptic cleft Postsynaptic cell Voltage gated Ca2 channel 2013 Pearson Education Inc Figure 8 19a ESSENTIALS Synaptic Communication Slide 3 An action potential depolarizes the axon terminal The depolarization opens voltage gated Ca2 channels and Ca2 enters the cell Calcium entry triggers exocytosis of synaptic vesicle contents Synaptic vesicle with neurotransmitter molecules Synaptic cleft Action potential arrives at axon terminal Docking protein Ca2 Postsynaptic cell Voltage gated Ca2 channel 2013 Pearson Education Inc Figure 8 19a ESSENTIALS Synaptic Communication Slide 4 An action potential depolarizes the axon terminal The depolarization opens voltage gated Ca2 channels and Ca2 enters the cell Calcium entry triggers exocytosis of synaptic vesicle contents Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell Synaptic vesicle with neurotransmitter molecules Synaptic cleft Receptor Action potential arrives at axon terminal Docking protein Ca2 Postsynaptic cell Voltage gated Ca2 channel 2013 Pearson Education Inc Figure 8 19a ESSENTIALS Synaptic Communication Slide 5 Synaptic vesicle with neurotransmitter molecules Synaptic cleft Receptor An action potential depolarizes the axon terminal The depolarization opens voltage gated Ca2 channels and Ca2 enters the cell Calcium entry triggers exocytosis of synaptic vesicle contents Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell Neurotransmitter binding initiates a response in the postsynaptic cell Action potential arrives at axon terminal Docking protein Ca2 Postsynaptic cell Voltage gated Ca2 channel Cell response 2013 Pearson Education Inc Cell to Cell Events at the Synapse Kiss and run pathway Vesicles fuse with membrane at the fusion pore Neurotransmitters pass through a channel Vesicles pull back from fusion pore 2013 Pearson Education Inc Figure 8 19b ESSENTIALS Synaptic Communication Neurotransmitter Termination Neurotransmitter action terminates when the chemicals are broken down are taken up into cells or diffuse away from the synapse Blood vessel Axon terminal of presynaptic cell Synaptic vesicle Glial cell Postsynaptic cell Enzyme Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells Enzymes inactivate neurotransmitters Neurotransmitters can diffuse out of the synaptic cleft Figure 8 19b ESSENTIALS Synaptic Communication Slide 1 Neurotransmitter action terminates when the chemicals are broken down are taken up into cells or diffuse away from the synapse Blood vessel Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells Axon terminal of presynaptic cell Synaptic vesicle Postsynaptic cell Glial cell 2013 Pearson Education Inc Figure 8 19b ESSENTIALS Synaptic Communication Slide 2 Neurotransmitter action terminates when the chemicals are broken down are taken up into cells or diffuse away from the synapse Axon terminal of presynaptic cell Synaptic vesicle Blood vessel Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells Enzymes inactivate neurotransmitters Glial cell 2013 Pearson Education Inc Postsynaptic cell Enzyme Figure 8 19b ESSENTIALS Synaptic Communication Slide 3 Neurotransmitter action terminates when the chemicals are broken down are taken up into cells or diffuse away from the synapse Blood vessel Axon terminal of presynaptic cell Synaptic vesicle Postsynaptic cell Enzyme Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells Enzymes inactivate neurotransmitters Neurotransmitters can diffuse out of the synaptic cleft Glial cell 2013 Pearson Education