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CORNELL BIOG 1440 - Practice Prelim II

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StuDocu is not sponsored or endorsed by any college or universitySample/practice exam 3 December 2016, questions andanswersIntroductory Biology: Comparative Physiology (Cornell University)StuDocu is not sponsored or endorsed by any college or universitySample/practice exam 3 December 2016, questions andanswersIntroductory Biology: Comparative Physiology (Cornell University)Downloaded by yelena radutskaya ([email protected])lOMoARcPSD|34545411 Practice Prelim II March 17, 2011 BioG 1440 Name: _______________________________________________________ Student ID #: _________________________________________________ “By signing below, I acknowledge that I am abiding by Cornell University’s Code of Academic Integrity.” Signature: ___________________________________________________ PLEASE: 1. WRITE YOUR NAME on all pages of the exam. 2. Record your answers to all multiple choice, true/false, and matching questions directly on the exam. 3. Write legibly. If we cannot read your answer, we cannot grade it. 4. Use only the space provided. 5. Do NOT use calculators or any other electronic devices. WATCH YOUR TIME! This is a 50 minute test. Total pages in exam including cover: Multiple choice: ____ (pts) Short answer: Page 6 ____ (pts) Total Score = _____ out of Downloaded by yelena radutskaya ([email protected])lOMoARcPSD|34545412 MULTIPLE CHOICE (3 points each) For each of the following questions, please choose the SINGLE BEST answer. 1. What is the primary cause of an action potential along an axon? a. A switch in the external and internal concentration of K+ b. The release of a transmitter from a presynaptic cell. c. Changes in the membrane permeabilities of ions d. The injection of current into the cell e. Decrease in the membrane permeability to Na+ 2. When an action potential arrives at the presynaptic ending which response plays a direct role in the release of the neurotransmitter? a. An increase in EK b. An influx of Ca++ c. An increase in the influx of Na+ d. An increase Vm e. All of the above 3. Which of the following explains why myelination increases speed of the action potential? a. Myelination decreases the internal resistance of the axon b. Myelination decreases the membrance capacitance c. Myelination increases membrane resistance d. Both A & B are correct e. Both B & C are correct 4. Which of the following statements concerning Excitation-Contraction coupling is false? a. The transverse-tubules (T-tubules) are a continuation of the sarcoplasmic reticulum. b. The T-tubules transfer the membrane depolarization to the sarcoplasmic reticulum. c. The sarcoplasmic reticulum is a major Ca++ storage site. d. Ca++ released from the sarcoplasmic reticulum triggers the muscle contraction. e. ATP is required for excitation-contraction coupling. Downloaded by yelena radutskaya ([email protected])lOMoARcPSD|34545413 5. Which statement concerning the physiology of neuromuscular junction (NMJ) is true? a. With each action potential the presynaptic ending releases a single quanta of transmitter b. When a toxin is used to block action potentials in the motor neuron no activity is recorded in the muscle fiber near the NMJ c. When acetylcholine binds to its receptors the associated channels opens to allow both Na+ and K+ ions to flow d. After its release at the NMJ Ach is removed from the synaptic cleft via endocytosis e. Na+ entering the presynaptic ending is directly responsible for triggering the fusion of the synaptic vesicles and the release of the neurotransmitter 6. How many neurons are needed to pass sensory information from your little toe to the toe region of your sensory cortex? a. one b. two c. three d. four 7. Which of the following is the physiological basis for the difference in sensation between fast/sharp vs. slow/burning pain? a. free vs. enclosed nerve endings in the sensory neuron b. presence vs. absence of a specialized pain receptor cell c. myelinated vs. unmyelinated axon in the sensory neuron d. short vs. long axon in the sensory neuron 8. Which of the following is NOT induced by the sympathetic nervous system? a. sweat stimulation b. skeletal muscle blood vessel constriction c. pupil dilation d. immune deactivation e. B and D SHORT ANSWERS (4 points each) Downloaded by yelena radutskaya ([email protected])lOMoARcPSD|34545414 Using PEN, write your answers in the space provided below, observing sentence and space limits. Think about your answer before you begin writing. 11. Why does increasing the diameter of an axon result in an increase in the propagation speed of an axon? The membrane resistance (Rm) decrease proportionally with axon diameter while the internal resistance deceases as the square of the diameter. As a result the space constant λ (Rm /Ri) increases linearly with axon diameter. 12. A friend is studying the response of a squid giant axon to the injection of current. He has a recording electrode in the axon and is using a stimulator to inject a series of current pulses through a second electrode. The results of his experiments are summarized in the figure below. Initially your friend sets the stimulator to deliver one current pulse every 10ms. He observed that each current pulse triggered a single action potential (part A of the figure). However, as he increased the rate of the current injections he was surprised to see that they sometimes failed to trigger an action potential. Part B of the figure summarizes his results at a stimulus rate of one stimulus every 2 ms. Explain why increasing the stimulus rate can result in the failure to elicit an action potential. At the higher stimulus rates every other stimulus occurred during the refractory period. Downloaded by yelena radutskaya ([email protected])lOMoARcPSD|34545415 14. The neuromodulator dopamine plays a key role in regulating the activity of neurons in the striatum. a. How would the loss of dopamine’s excitatory input to the striatum influence disinhibition in the basal ganglia circuit that goes from striatum to globus pallidus to thalamus and finally to the motor cortex? The basal ganglia play a key role in the planning, selection and initiation of motor activity. Normally, the Basal Ganglia serves as a gate to inhibit/limit motor. The basal ganglia consists of a series of


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