MIT Department of Biology 7.013: Introductory Biology - Spring 2004 Instructors: Professor Hazel Sive, Professor Tyler Jacks, Dr. Claudette Gardel 7.013 Problem Set 6 FRIDAY April 9nd, 2004 Problem sets will NOT be accepted late. Question 1 A. Boston Red Sox Fran No. 1 has dissected the following neuron and needs your help to label its parts. Use the words from Column A below. Figure by MIT OCW. B. Match the following terms in Column A with their corresponding functions in Column B Column A Column B _________Axon Terminal a) Part of a neuron that transmits an electrical signal to another neuron _________Nodes of Ranvier b) Short, highly branched fiber that carries signals toward the cell body of a neuron _________Cell Body c) Layers of Schwann cells that coat the Dendrites axons of many neurons and help to conduct electrical impulses along axons. _________ Myelin Sheath d) The part that contains the nucleus and most of the cytoplasm and organelles. _________Dendrite e) The part of the neuron where action potentials are generated. f) A gap between two of the Schwann cells that make up an axon's myelin sheath; _________axon serves as a point for generating a nerve impulse _________axon hillock g) region along which the axon potential propagates 1 BASIC NEURON DESIGNQuestion 2 Jon Cucabura with a PhD in Logarithmic Mutations is studying three mutant neurons named Zoolander, Sketch, and BitLip. Below is a diagram of a representative action potential. Using this diagram as a template carefully draw any change(s) that would occur in the structure of the action potential as a result of the mutations. Zoolander:mutation resulting in a cell lacking the voltage-gated K+ channel Sketch:Mutation resulting in a cell lacking the voltage-gated Na+ channel BitLip: Mutation that completely blocks the neuron terminus voltage-gated Ca++ channel pump. -80 1 2 3 4 5 6 -60 -40 -20mV 0 20 40 msec Threshold Threshold Threshold ZOOLANDER -80 1 2 3 4 5 6 -60 -40 -20mV 0 20 40 msec -80 1 2 3 4 5 6 -60 -40 -20mV 0 20 40 msec SKETCH Voltage Voltage Voltage BIT LIP Figure by MIT OCW. 2Question 3 SlowMo is a nerve gas that works by irreversibly interacting with a serine residue in the active site of acetylcholinesterase, the enzyme responsible for removing acetylcholine (ACh) from the synaptic cleft. SlowMo causes death by affecting the muscles involved in breathing. Explain, at the molecular level, how this might occur. Question 4 A. Answer True or False.1. Cone cells sense colors and Rod cells sense black, white and depth.2. A neuron cannot refire during the refractory period. 3. Neuron guidance is aided by both attractive and repulsive chemotaxes.B. Multiple Choice1. During chemical synaptic transmission, which of the following sequences of eventsoccurs in a presynaptic neuron? Depolarization of the terminal --> Ca2+ entry --> AP in axon --> vesicle fusion --> transmitter release. AP in axon --> depolarization of the terminal --> Ca2+ entry --> vesicle fusion --> transmitter release. Ca2+ entry --> AP in axon --> vesicle fusion --> depolarization of the terminal --> transmitter release. depolarization of the terminal --> AP in axon --> Ca2+ entry --> vesicle fusion --> transmitter release. 2.Which of the following substances is capable of functioning as a neurotransmitter? a. acetylcholineb. glutamic acidc. nitric oxided. glycinee. aspartic acidf. epinephrineg. all of the above function as neurotransmitters.33. "Sodium inactivation" refers toa. the inability of sodium to move across the membrane.b. the expulsion of sodium from the neuron by the sodium pump.c. the movement of sodium during presynaptic inhibition.d. the closing of the sodium channels a short time after they have opened.4. Nodes of Ranvier area. places where two neurons can communicate.b. the gaps in the myelin sheath of a neuron.c. points of contact between a neuron and a glial cell. d. swellings on an axon where transmission can take place.5. IPSP (Inhibitory postsynaptic potential) stimulates a neuron to a. depolarize.b. repolarize.c. hyperpolarize.d. stay in resting state6. Binding between a transmitter substance and a receptor moleculea. requires ATP.b. can take place only in the presence of calcium ions.c. is a temporary association that breaks spontaneously.d. is a stable association that must be broken by specialized enzymes.7. Temporal summation is made possible by a. the fact that postsynaptic potentials spread some distance from their point of origin.b. the fact that postsynaptic potentials last some time after their instance of generation.c. the increase in size of postsynaptic potentials in a series.d. the nature of the ion channels that open at the synapse.8. The all-or-none principle of nerve action states thata. the entire length of the nerve conducts an action potential or no part does.b. an action potential always reaches its maximum strength or it doesn't appear at all.c. all available ions contribute to the rise and fall of the action potential or none do.d. all synapses on a neuron must be active in order for them to excite another neuron or muscle. 9. In the growing embryo, axons migrate along paths “paved” witha. ephrin ligandsb. ephrin receptorsc. laminind. netrin4Question 5 Early one morning, two scientists Chil and Praig are sharing chocolate chip pancakes at IHOP, after a long night of intense experimentation with a protein called Joi-NT (a neurotransmitter) in their laboratory. When the waitress, MoAss, brings them the check, they scramble for their wallets, and soon realize that they must have forgotten them in the lab. Not knowing what to do, and having a tendency to act impulsively, they come up with a plan to race out of the IHOP when MoAss goes into the back kitchen, since they’re the only customers at the restaurant. As soon as she leaves the seating area, Praig leaps out of his seat, sprints to the door, and starts making his way through the parking lot and down Peter Pan Ave. Chil, acting rather chill, calmly walks out of the IHOP, confident that he’s too good to get caught. Just as the door shuts behind him, MoAss sees that no money has been left on the table and that they have already left. She immediately drops the dishes in her hands, and starts running after the two scientists. Surprise! Chil hears her coming, and takes off sprinting towards Praig. Chil and Praig run all the way to their lab, JoiNTville. During their sprint home, the two scientists notice that their
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