Homework #1

EEMB 160 : The Neural Basis of Behavior, "Neurobehavior"

NAME: Email address: Due: April 24 (Monday) in lecture!! Covers approximately lectures 4/5 through 4/19 & all associated readings. Covers discussion sections 1st week, 2nd week & 3rd week Covers web modules 1 & 2 25 points total You can complete this assignment through the web site and then print it to turn it in. (Try clicking on the buttons to choose your answer on the multiple choice questions and type your short answers or single word answers in the text boxes provided below the question.) IF YOU DO DECIDE TO PRINT YOUR ANSWERS VIA THE BROWSER, PLEASE BE SURE TO PROOFREAD THE ASSIGNMENT BEFORE TURNING IT IN TO MAKE SURE ALL YOUR ANSWERS APPEAR, ESPECIALLY THE MULTIPLE CHOICE ANSWERS! Also, links (underlined, blue text) within the questions or answers are NOT indicating the answer, but take you to a part of a module that might help you with the question. In addition to lecture material, you may need to look at all the modules 1 & 2. If you are still having problems, come see me (Carrie) in office hours or make an appointment (before the assignment is due). Address: http://lifesci.ucsb.edu/~mcdougal/neurobehavior/modules_homework/2000hw1.html A note about doing your assignment on-line, WATCH OUT FOR NETSCAPE OR INTERNET EXPLORER CRASHING IN THE MIDDLE OF YOU TYPING IN YOUR ANSWERS (YOU'LL LOSE ALL YOU'VE TYPED)!! It might be a good idea to have some answers written out or have them pasted into a program that is saveable (like Word or a text editor). Also, after you print your assignment, look through it to make sure all your answers printed, especially examine questions #16 & #20. Also, make sure the right margin is not cut off, truncated your answers. Printing Instructions: If you use Internet Explorer you should just be able to print away (might want to make sure that "fit to page" is checked under Print Preview mode. If you have Netscape, all bets are off--I'll try to make the page skinny enough to fit on one page. Then go to print. WRITE (OR TYPE) YOUR ANSWERS ON THIS SHEET!!

1. [2 pts] What is the value of studying the behavior of simple organisms? Explain at least 2 reasons.   2. [1 pt] Cuvier came up with a theory of how bats navigate & catch insects without using vision. Even though this theory was not correct (he unbelievably thought they used the sense of touch to navigate), why was his theory still important scientifically?   3. [2 pts] (a) was the scientist that did the preliminary field studies of moth behavior in response to bat-like supersonic sounds. What two behaviors in these night-flying moths were discovered from these field studies (describe briefly)? (b) What was the next step that this scientist took in elucidating the moth’s behavior? Briefly describe the results and the study performed.     4. [1 pt] Here are two pairs of recordings from 4 different cells: one synapse occurs between each pair of cells. There is one microelectrode that records from the presynaptic cell, and another that records from the postsynaptic cell. One pair of recordings comes from a chemical synapse and the other from an electrical synapse. Which is which AND state two distinguishing features that allowed you to make your determination.   5. [1 pt] (a) List two advantages to having electrical synapses in neural circuits?   (b) List two advantages to having chemical synapses in neural circuits?   6. [1 pt] Does every neuron use an AP to transmit a signal from its input region to its output region? Explain why or why not.     7. [1 pt] (a) What causes the depolarization phase of the AP, explain briefly.   (b) What causes the repolarization phase of the AP, explain briefly.   8. [2 pts] The passive properties of the membrane (aka cable properties) are what determine how far electrical signals can travel inside the neuron. The mathematical term to describe how far a signal can travel before significant degradation occurs is the . There are 3 properties of the membrane that determine this. (1), which is how easily the charge or current (i.e. the signal) can leave the neuron across the membrane, which would result in signal degradation. This first property was most affected by the evolution of . (2), which is how easily the charge or current can flow within the neuron or axon without being impeded by intracellular structures. This property is most directly affected by the of the neuron or axon. (3),which is the ability of the membrane to store or bind up some of the charge or current.     9. [1 pt] Why is it that dendrites are typically described as being chemically excitable, but not electrically excitable, but the axon is electrically excitable?   10. [1 pt] Which presynaptic neuron (choose between #1, 2 or 3) has the largest effect on changing the Vm (membrane potential) of the postsynaptic cell? (Assume all inputs are excitatory.) Explain why. 11. [1 pt] In vertebrates, (a) functions to insulate an axon to maximize the distance currents (movement of ions) can flow inside the axon. The small bare parts of the axon in between these regions are called (b). It is in these areas (b) that currents flow across the axon membrane to regenerate the action potential. How is this region (b) of the axon membrane specialized to this function?   12. [1 pt] Using the lobster stretch receptor, was able to demonstrate the mechanism of the inhibitory neurotransmitter, . This neurotransmitter causes Cl- channels to open on the postsynaptic cell, which results in Cl- rushing into the cell. The membrane potential of the postsynaptic cell is then said to be . Whenever a neuron is hyperpolarized, it is much more difficult to stimulate that neuron to reach and trigger an AP.   13. [2 pts] There were two examples described in lecture of very primitive organisms that demonstrate that whereas they may not have a true nervous system, they have many of the components of nervous systems. Organism Sensory Input What is Effector & How is it modfied by the sensory input? What is the associated change in membrane potential?   14. [1 pt] Polychaetes are a group of segmented worms within the phylum , that have a great variety of nervous system complexity. We can understand this difference in nervous system complexity by examining this group of worms’ behavior and anatomy. Here are two polychaetes that exhibit this range of complexity within this group. Myxicola sp. A tube-dwelling polychaete. Never comes out of its tube, only fan-like feeding apparatus sticks out. Nereis sp. An errant polychaete. Actively crawls and swims around searching for food--a predator. Which worm do you think has a more complex nervous system and WHY?   15. [2 pts] Cnidarians (aka Coelenterates) have many unusual properties in the structure and organization of their nervous systems. Briefly describe two unique features of this group’s nervous systems AND explain why this group has evolved these unique features—how is this group different anatomically?   16. [0.5 pt] Signals from mechanoreceptors would be carried by which type of axon? Choose all that apply. Sensory Ganglions Interneruons Motor Afferent Efferent   17. [0.5 pt] The primary feature of a sensory neuron is whereby stimuli is taken in from a different environment and made "readable" to the nervous system.   18. [1 pt] Statocysts are a type of -receptor that specifically are specialized to detect . Organisms with statocysts generally use them to .   19. [1 pt] The following recordings from 2 different types of sensory neurons show the response of those sensory neurons’ axons to the appropriate suprathreshold stimulus of a certain duration and intensity. (a) Which recording displays a sensory neuron that responds to constant stimulus strength? A B (b) Which recording displays a sensory neuron that responds to a change in stimulus strength? A B (c) Which is more common in sensory neurons and what is this process called? A B (d) Name of process:   20. [2 pts] Two separate intracellular recordings from a mechanosensory neuron produce the following results:   (a) What are either of these signals called specifically in sensory neurons? (b) Which represents a stronger stimulus? A B (c) Which will code for a higher frequency of APs in a given time? A B (d) Why?   Return to Modules & Homework Page Return to Home Page