1. Fill in the blanks. Chemical messengers called (1) ___
attach to receptor sites on the
(2) of the receiving neuron. When enough of those excitatory chemical messengers are attached, the neuron reaches the point of firing called (3) .
Neurons either fire or they don't. There is no "sort of" firing. This is called an (4) response. The firing is called a neural impulse - also called an (5) .
The neural impulse travels down the length of the (6) to the
distant ends of the neuron called the (7) . This causes the chemical
messengers to be released into the empty spaces between neurons called the (8) where they float across to the receptor sites on the receiving neuron, and the whole process repeats.