PSY 342 Lecture Notes - Lecture 1: Axon Terminal, Neurotransmission, Acetylcholine
Chapter 1
Neurotransmission
• Can be described in many ways: anatomically, chemically, electrically
• Anatomical
o Neurons and the connections between them, called synapses
o Synapses can form on many parts of a neuron, not just the dendrites as axodendritic synapses, but also on the
soma as axosomatic synapses, and even at the beginning and at the end of axons
▪ Asymmetric
• Chemical
o How chemical signals are coded, decoded, transduced, and sent along the way
Neurons
• Soma: cell body
• Receive information from other neurons through dendrites
• Send information to other neurons via an axon
Neurotransmitters
• Serotonin
• Norepinephrine
• Dopamine
• Acetylcholine
• Glutamate
• GABA (γ-aminobutyric acid)
Classic Neurotransmission
• Neurons send electrical impulses from one part of the cell to another part of the same cell via their axons
o These electrical impulses do not jump directly to other neurons.
o Communication between neurons is chemical not electrical
• Involves one neuron hurling a chemical messenger, or neurotransmitter, at the receptors of a second neuron
• Steps
o An electrical impulse in the first neuron is converted to a chemical signal at the synapse
▪ Excitation-secretion coupling
• An electrical impulse in the first – or presynaptic - neuron is converted into a chemical signal at
the synapse.
• Once an electrical impulse invades the presynaptic axon terminal, it causes the release of
chemical neurotransmitter stored there
o Electrical impulses open ion channels by changing the ionic charge across neuronal
membranes
• Sodium flows in through sodium channels on the axon causing an action potential
• Once the action potential reaches the axon terminal, calcium channels open and calcium enters.
• Synaptic vesicles spill their contents in the synaptic cleft.
▪ Occurs from the presynaptic axon terminal to the postsynaptic neuron
o Neurotransmission continues in the second neuron either by
▪ Converting the chemical information from the first neuron back into an electrical impulse in the second
neuron.
▪ Chemical information from the first neuron triggering a cascade of further chemical messages within the
second neuron to change that neuron’s molecular and genetic functioning
Retrograde Neurotransmission
