3Nerve impulse Action potential travels along an axon Information passes from presynaptic neuron to postsynaptic cell
4General properties of synapses ElectricalRarePre- and postsynaptic cells are bound by interlocking membrane proteins
5General properties of synapses Chemical synapsesMore commonExcitatory neurotransmitters cause depolarization and promote action potential generationInhibitory neurotransmitters cause hyperpolarization and suppress action potentials
6Cholinergic 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
7Figure 12.19 The Function of a Cholinergic Synapse PLAYAnimation: Overview of a cholinergic synapseFigure
8Figure 12.19 The Function of a Cholinergic Synapse
10NeuromodulatorsInfluence 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
20Presynaptic inhibition GABA release at axoaxonal synapse inhibits opening calcium channels in synaptic knobReduces amount of neurotransmitter released when action potential arrives
21Figure 12.24 Presynaptic Inhibition and Facilitation
22Presynaptic facilitation Activity at axoaxonal synapse increases amount of neurotransmitter released when action potential arrivesEnhances and prolongs the effect of the neurotransmitter
23Figure 12.24 Presynaptic Inhibition and Facilitation
24Rate 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
25Rate 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
26You 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.
27You 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.