That first neuron ended shortly after entering the spinal cord, where its axon terminal formed a connection, called a/an [a], with an interneuron in the [b] [c] of the spinal cord. Here, the first neuron released a/an [d] into the synaptic cleft, where it bound to a/an [e] that was "listening" for it on the membrane of the post-synaptic ("downstream") cell. So far, the membrane potential of the post-synaptic cell was "resting" at [x] mV. The binding event, however, opened [f] channels on the interneuron, allowing positive charges to trickle in. These charges started a/an [g] potential traveling toward the [h] of the interneuron, which "summed up" each incoming pain signal until the [i] potential was was reached at [y] mV. Once this value was crossed, voltage-gated [k] channels popped open and the membrane "depolarized" to a value of [z] mV. This depolarization caused channels further down the cell to pop open, and a chain reaction began. As a result, a/an [l] potential traveled all the way down the [m] of the interneuron until it reached the synaptic knobs that connected to the next neuron in line, where [n] ions rushed in, causing the interneuron to release its own [o] into the synaptic cleft. ANSWERS:

action

afferent

axon

axon hillock

calcium

chloride

cranial

dendrite

dorsal/posterior

efferent

extend

flex

funiculus

graded/local

horn

neurotransmitter

potassium

receptor

reflex

sodium

spinal

synapse

threshold

ventral/anterior

30

-55

-70

-80