Questions for Nervous Systems 1.  Draw a neuron and label its parts. What would be the most obvious difference if you were looking at a vertebrate motor neuron vs. say the neuron that stimulates the tail-flip escape reflex in crayfish? What cell type produces this difference and, in general terms, what is its functional significance? If you instead compared the neuron driving an escape reflex in a squid with one involved in, say, digestion or some other less critical function, what would be the most obvious difference? What, in very general terms, is the functional significance of this?
.

2.  When there is a blockage of blood flow to a region of the brain, we say that a stroke has occurred. Neuronal death begins to occur quickly following such a blockage. What two features predispose them to quick death this way and then make this damage so devastating in the long term?


3,  Explain how the membrane potential is generated. Give special attention to proteins that move or allow movement of ions.


4. Now, explain how things change during an action potential. Related to this: neurons and are excitable cells. At the level of membrane proteins, what is the difference between an excitable cell and a non-excitable cell?


5. The action potential represents an unusual thing in biology — a positive feedback loop. Which part of the action potential am I referring to and what two things limit this response?


6.  What would each of the following compounds or treatments do to a neuron either at the axon or synapse?

• tetrodotoxin — blocks voltage-gated Na⁺ channels
• ouabain — blocks the Na⁺/K⁺ pump
• an infusion of K⁺ into the extracellular space
• a decrease of K⁺ in the extracellular space
• blockage of non-gated K⁺ channels
• blockage of voltage-gated K⁺ channels
• blockage of voltage-gated Ca²⁺ channels

7.  How does an action potential move down an axon? What two basic ways can it be ‘transmitted’ to the next neuron? What molecules or structures are critical for each type of transmission?