Psychology 1000 Study Guide - Quiz Guide: Botulism, Disinhibition, Curare
3 Jun 2018
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Synaptic Transmission
• Otto Loewi discovered that neurons release chemicals to pass over to next neuron
• Researchers found synaptic cleft between axon terminals of one neuron and dendrite of
the next
• Neurons produce neurotransmitters to carry messages across synapse to excite or
inhibit other neurons
o Process involves five steps:
▪ Synthesis – chemical molecules formed inside neuron
▪ Storage – molecules stored in synaptic vesicles
▪ Release – Action potential causes vesicle to move to surface of terminal,
molecules are released into fluid-filled space
▪ Binding – molecules cross the space and bind to receptor sites (large
protein molecules embedded in the membrane)
▪ Deactivation
o Binding of neurotransmitters to receptor site causes two possible effects:
▪ Excitation – depolarizes the postsynaptic cell membrane by stimulating
flow of Na+ (excitatory transmitters)
▪ Inhibition – hyperpolarizes the postsynaptic cell membrane by
stimulating ion channels that allow K+ to flow out of the neuron, or
negatively charged ions to flow in (changes potential from –70 mV to –72
mV)
• Makes it more difficult for excitatory transmitters at other
receptor site to depolarize the neuron to the threshold
o Neurotransmitters continue to function until deactivation:
▪ Some deactivated by other chemicals in synaptic space that break them
down
▪ Reuptake – transmitters reabsorbed into presynaptic axon terminal
o Examples of neurotransmitters:
▪ Acetylcholine (Ach) – functions in excitatory and inhibitory systems
(related to memory, motor, behavioural inhibition)
▪ Norepinephrine (NE) – functions in excitatory and inhibitory systems
(related to arousal, eating)
▪ Dopamine (DA) – functions in inhibitory, sometimes excitatory, systems
(related to arousal, voluntary movement)
▪ Seratonin (5-HT) – functions in inhibitory and excitatory systems (related
to sleep, thermoregulation)
▪ Gamma Aminobutynic Acid (GABA) – functions in inhibitory systems
(related to motor behaviour)
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