Second Messenger: A chemical signal, such as calcium ion or
cyclic AMP that relays a hormonal message from a cell's surface
to its interior. Signal Transduction Pathway: A mechanism
linking a mechanical or chemical stimulus to a cellular
response. Substrate Level Phosphorylation: The formation of ATP
by directly acting transferring a phosphate group to ADP from an
intermediate substrate in catabolism. Synapse: The locus where
one neurone communicates with another neurone in a neural
pathway; a narrow gap between a synaptic terminal of an axon and
a signal receiving portion (dendrite or cell body) of another
neurone or effector cell. Neurotransmitter molecules released by
synaptic terminals diffuse across the synapse, relaying messages
to the dendrite or effector. Synaptic Terminal: A bulb at the
end of an axon in which neurotransmitter molecules are stored
and released. Transcription: The transfer of information from a
DNA molecule into an RNA molecule. Transcription Factor: A
regulatory protein that binds to