THOUGHT QUESTIONS

Why does synaptic transmission involve the release of chemicals? Direct electrical coupling of neurons is far simpler, so why do our neurons not use it more extensively? (A tiny percentage of synaptic connections in the human brain do not use electrical coupling). Normally, nature uses the simplest means possible to a given end, so there must be some advantages to chemical transmission. What do you think they are?
Consider the control of the withdrawal reflux illustrated in Figure 11. Could you design a circuit using electrical synapses that would accomplish the same task?

KEY CONCEPTS

Neurons communicate by means of synapses, which enable the presynaptic neuron to produce excitatory or inhibitory effects on the postsynaptic neuron. These effects increase or decrease the rate at which the axon of the postsynaptic neuron sends action potentials down to its terminal buttons.
When an action potential reaches the end of an axon, it causes some synaptic vesicles to release a neurotransmitter into the synaptic cleft. Molecules of the neurotransmitter attach themselves to receptors in the postsynaptic membrane.
When they become activated by molecules of the neurotransmitters, postsynaptic receptors produce either excitatory or inhibitory postsynaptic potentials by opening neurotransmitter-dependent sodium, potassium, or chloride ion channels.
The postsynaptic potential is terminated by the destruction of the neurotransmitter or by its reuptake into the terminal button.
Autoreceptors help to regulate the amount of neurotransmitter that is released.
Axoaxonic synapses consist of junctions between two terminal buttons. Release of neurotransmitter by the first terminal button increases or decreases the amount of neurotransmitter released by the second.
Neuromodulators and hormones have actions similar to those of neurotransmitters: They bind with and activate receptors on or in their target cells.

	Erstellt von Lorann Kearney vor mehr als 9 Jahre

Notes for Chapter 2 of Foundations of Behavioral Neuroscience