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Animations
(Animation Requirements)

• Development of Membrane Potential
• Action Potential
• Stroke
• Reflex Arc
• Sense of Balance
• Sense of Rotational Acceleration
• Taste
• Smell
• Hearing
• Vision

Art Labeling Activities

• Central Nervous System
• Synapse Structure and Function

Learning. Some of the most exciting biology being done today is in neurobiology, where researchers working at the molecular level are beginning to unravel the mystery of memory and learning.

1. Scientists begin to understand learning at the molecular level.
2. Nobel winners show how long-term changes in the brain create mood.
3. Sometimes I wonder if my dog is smarter than I am.
4. One surprisingly small region of the brain is responsible for humans' general intelligence.
5. Simple repetition can have a powerful impact on learning.
6. Pulling an all-nighter doesn't work because learning requires sleep.
7. Lab rats are able to control a robot by thought alone.

Doin' Drugs
Addictive drugs like cocaine or nicotine act at the level of individual synapses within the brain. Typically the drug produces euphoria by stimulating the synapses of pleasure-producing pathways. Cocaine, for example, blocks the reabsorption of the neurotransmitter dopamine in nerve synapses of the limbic system. Cocaine molecules bind tightly to the dopamine-recycling proteins, with the result that more and more dopamine builds up in the synapse, causing the postsynaptic neuron to fire more often, increasing pleasure. Addiction results when the brain attempts to "turn the volume" back down by removing dopamine receptors from the postsynaptic membrane. If you subsequently stop adding cocaine, so that dopamine levels fall to normal, there are not enough "target" postsynaptic receptors to fire the pleasure-producing pathway! To feel even normal, you again take cocaine to re-elevate dopamine levels. You are addicted. The deep lesson of doin' drugs is that addiction is not a matter of will power or moral character--it is just chemistry. You can no more avoid addiction than you can command a bullet speeding toward your head to stop. The way to avoid the bullet is not to pull the trigger.

How Can Snails "See" an Invisible Trail
We humans are quite dependent on our senses of sight and sound. Many organisms have evolved other senses, more suited to their particular environments and life styles. Gastropod mollusks, for example, deposit mucous trails while crawling over surfaces that other snails of the same species follow. The stimuli in the mucus and the sense organ used by snails to follow the trail are unknown. The hypothesis that originally received the most attention was that the trail contained a chemical concentration gradient which allowed snails to follow the trail in the same direction that it was laid down ("trail polarity"). This hypothesis has been rejected, however, as it conflicts with many experimental observations. Development of alternative hypotheses about how a snail detects the direction of a trail would be greatly aided by a more detailed understanding of the sensory organ involved. Paul Hamilton of the University of Central Arkansas studied the involvement of the cephalic tentacles of the marsh periwinkle snail, Littoraria irrorata, on detecting trail polarity. By amputating tentacles, he was able to investigate the role of the tentacles in detecting mucous trail polarity.