Chapter 13 Outline
Synaptic Transmission Is Usually Chemical but Can Be Electrical
- Electrical synapses transmit signals instantaneously
- Chemical synapses can modify and amplify signals
Synaptic Potentials Control Neuronal Excitability
- Synapses onto a spinal motor neuron exemplify functions of fast synaptic potentials
- Synapses excite or inhibit a neuron by depolarization or hyperpolarization at the site of impulse initiation
Fast Chemical Synaptic Actions Are Exemplified by the Vertebrate Neuromuscular Junction
- Chemical synapses work by releasing and responding to neurotransmitters
- Postsynaptic potentials result from permeability changes that are neurotransmitter-dependent and voltage-independent
- EPSPs between neurons resemble neuromuscular EPSPs but are smaller
- Fast IPSPs can result from an increase in permeability to chloride
Presynaptic Neurons Release Neurotransmitter Molecules in Quantal Packets
- Acetylcholine is synthesized and stored in the presynaptic terminal
- Neurotransmitter release requires voltage-dependent Ca2+ influx
- Neurotransmitter release is quantal and vesicular
- Synaptic vesicles are cycled at nerve terminals in distinct steps
- Several proteins play roles in vesicular release and recycling
Neurotransmitters Are of Two General Kinds
- Neurons have one or more characteristic neurotransmitters
- An agent is identified as a neurotransmitter if it meets several criteria
- Vertebrate neurotransmitters have several general modes of action
- Neurotransmitter systems have been conserved in evolution
Postsynaptic Receptors for Fast Ionotropic Actions: Ligand-Gated Channels
- ACh receptors are ligand-gated channels that function as ionotropic receptors
- Many, but not all, ligand-gated channel receptors have evolved from a common ancestor
Postsynaptic Receptors for Slow, Metabotropic Actions: G Protein–Coupled Receptors
- G protein–coupled receptors initiate signal transduction cascades
- Metabotropic receptors act via second messengers
- Other mechanisms of G protein–mediated activity
- G protein–coupled receptors mediate permeability-decrease synaptic potentials and presynaptic inhibition
Synaptic Plasticity: Synapses Change Properties with Time and Activity
- Neurotransmitter metabolism is regulated homeostatically
- Learning and memory may be based on synaptic plasticity
- Habituation and sensitization in Aplysia
- Long-term potentiation in the hippocampus
- BOX 13.1 Synapse Formation: Competing Philosophies, Matthew S. Kayser
- Long-term potentiation is a necessary component of learning