Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Action potential travels along an axon Information passes from presynaptic neuron to postsynaptic cell Nerve impulse

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Rare Pre- and postsynaptic cells are bound by interlocking membrane proteins General properties of synapses

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical synapses More common Excitatory neurotransmitters cause depolarization and promote action potential generation Inhibitory neurotransmitters cause hyperpolarization and suppress action potentials General properties of synapses

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Release acetylcholine (ACh) Information flows across synaptic cleft Synaptic delay occurs as calcium influx and neurotransmitter release take appreciable amounts of time ACh broken down Choline reabsorbed by presynaptic neurons and recycled Synaptic fatigue occurs when stores of ACh are exhausted Cholinergic synapses

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Animation: Overview of a cholinergic synapse PLAY Figure The Function of a Cholinergic Synapse Figure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure The Function of a Cholinergic Synapse Figure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Adrenergic synapses release norepinephrine (NE) Other important neurotransmitters include Dopamine Serotonin GABA (gamma aminobutyric acid) Other neurotransmitters

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Influence post-synaptic cells response to neurotransmitter Neurotransmitters can have direct or indirect effect on membrane potential Can exert influence via lipid-soluble gases Neuromodulators Animation: Synaptic potentials, cellular integration, and synaptic transmission PLAY

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neurotransmitter Functions Figure 12.21a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neurotransmitter Functions Figure 12.21b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neurotransmitter Functions Figure 12.21c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Simplest level of information processing occurs at the cellular level Excitatory and inhibitory potentials are integrated through interactions between postsynaptic potentials Information processing

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings EPSP (excitatory postsynaptic potential) = depolarization EPSP can combine through summation Temporal summation Spatial summation IPSP (inhibitory postsynaptic potential) = hyperpolarization Most important determinants of neural activity are EPSP / IPSP interactions Postsynaptic potentials

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Temporal and Spatial Summation Figure 12.22a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Temporal and Spatial Summation Figure 12.22b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure EPSP – IPSP Interactions Figure 12.23

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings GABA release at axoaxonal synapse inhibits opening calcium channels in synaptic knob Reduces amount of neurotransmitter released when action potential arrives Presynaptic inhibition

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Presynaptic Inhibition and Facilitation Figure 12.24

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Activity at axoaxonal synapse increases amount of neurotransmitter released when action potential arrives Enhances and prolongs the effect of the neurotransmitter Presynaptic facilitation

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Presynaptic Inhibition and Facilitation Figure 12.24

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neurotransmitters are either excitatory or inhibitory Effect on initial membrane segment reflects an integration of all activity at that time Neuromodulators alter the rate of release of neurotransmitters Rate of generation of action potentials

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Can be facilitated or inhibited by other extracellular chemicals Effect of presynaptic neuron may be altered by other neurons Degree of depolarization determines frequency of action potential generation Rate of generation of action potentials

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings You should now be familiar with: The two major divisions of the nervous system and their characteristics. The structures/ functions of a typical neuron. The location and function of neuroglia. How resting potential is created and maintained.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings You should now be familiar with: The events in the generation and propagation of an action potential. The structure / function of a synapse. The major types of neurotransmitters and neuromodulators. The processing of information in neural tissue.