Neurotransmitters Are

Neurotransmitters are:

A) neurochemicals that are released into the synapses of neurons and which diffuse in milliseconds across synaptic gaps to activate or inhibit the receiving neuron or muscle fiber.
B) substances that are carried in the blood to affect organs that are sensitive to them.
C) diverse in size, including small molecules like adrenaline and larger molecules like peptides.
D) neuro-modulators that are released by some neurons and that diffuse some distance to affect many thousands of nearby neurons.