3 Nerve impulse Action potential travels along an axon Information passes from presynaptic neuron to postsynaptic cell
4 General properties of synapses ElectricalRarePre- and postsynaptic cells are bound by interlocking membrane proteins
5 General properties of synapses Chemical synapsesMore commonExcitatory neurotransmitters cause depolarization and promote action potential generationInhibitory neurotransmitters cause hyperpolarization and suppress action potentials
6 Cholinergic synapses Release acetylcholine (ACh) Information flows across synaptic cleftSynaptic delay occurs as calcium influx and neurotransmitter release take appreciable amounts of timeACh broken downCholine reabsorbed by presynaptic neurons and recycledSynaptic fatigue occurs when stores of ACh are exhausted
7 Figure 12.19 The Function of a Cholinergic Synapse PLAYAnimation: Overview of a cholinergic synapseFigure
8 Figure 12.19 The Function of a Cholinergic Synapse
9 Other neurotransmitters Adrenergic synapses release norepinephrine (NE)Other important neurotransmitters includeDopamineSerotoninGABA (gamma aminobutyric acid)
10 NeuromodulatorsInfluence post-synaptic cells response to neurotransmitterNeurotransmitters can have direct or indirect effect on membrane potentialCan exert influence via lipid-soluble gasesPLAYAnimation: Synaptic potentials, cellular integration, and synaptic transmission
20 Presynaptic inhibition GABA release at axoaxonal synapse inhibits opening calcium channels in synaptic knobReduces amount of neurotransmitter released when action potential arrives
21 Figure 12.24 Presynaptic Inhibition and Facilitation
22 Presynaptic facilitation Activity at axoaxonal synapse increases amount of neurotransmitter released when action potential arrivesEnhances and prolongs the effect of the neurotransmitter
23 Figure 12.24 Presynaptic Inhibition and Facilitation
24 Rate of generation of action potentials Neurotransmitters are either excitatory or inhibitoryEffect on initial membrane segment reflects an integration of all activity at that timeNeuromodulators alter the rate of release of neurotransmitters
25 Rate of generation of action potentials Can be facilitated or inhibited by other extracellular chemicalsEffect of presynaptic neuron may be altered by other neuronsDegree of depolarization determines frequency of action potential generation
26 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.
27 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.