1 Vertebrate Physiology 437 EXAM I NAME, Section (circle): am pm 23 September 2004. Exam is worth 100 points. You have 75 minutes. True or False (write true or false ; 10 points total; 1 point each) 1. Water is pumped across the cell membrane in the kidney in response to ADH (antidiuretic hormone) release from the hypothalamus. 2. At a synapse, changes in postsynaptic potential last longer than changes in postsynaptic current. 3. When an ion species moves across the membrane through open channels and changes the membrane potential, the concentration gradient for that ion is abolished and needs to be reestablished later using ATP. 4. Experiments with artificial electrical stimulation of axons indicate that action potentials can only go from the cell body toward the axon terminal. 5. Proteins contain more metabolizable energy per gram than fats or carbohydrates. 6. Muscarine is an acetylcholine receptor agonist. 7. If extracellular fluid is hypoosmotic with respect to nearby cells, water will tend to move out of the cells. 8. Calcium is the ion primarily responsible for the resting membrane potential observed in most vertebrate cells. 9. Increased strength of incoming sensory information is coded to the central nervous system via larger action potentials. 10. Both sodium and potassium ions move through open cholinergic receptor channels. Really Short Answer (maybe a few words or a sentence; 37.5 points total; 2.5 points each) 1. What are the Nernst and Goldman equations used for and how do they differ? 2. According to one of your lab readings, what evolutionary advantage(s) do diseases have over humans? 3. What is unusual about the ion concentrations found in the endolymph within the cochlea of the mammalian ear as compared to other extracellular fluids in the body? 4. What are two long-term methods by which vertebrate axons are able to increase the rate of action potential movement down axons?
2 5. How does signal transmission differ between neurons that communicate via a synapse as compared to neurons connected via gap junctions? 6. How does the mechanism of activity of fast chemical synapses (e.g., nicotinic acetylcholine) usually differ from that of slow chemical synapses (e.g., muscarinic acetylcholine)? 7. Why did KEB insist in lecture that 1) spatial and 2) temporal summation of postsynaptic potentials both have a temporal component? 8. What would be the effect on nervous system function if an individual was deficient in calcium? 9. Describe two ways the resting membrane of the axon hillock, and its integral membrane proteins, can be altered to be more likely to send an action potential down the axon. 10. At the protein level, what makes different photopigments in human cones different? 11. What is a horizontal streak in the context of vertebrate physiology? 12. During smolting, Atlantic Salmon increased tolerance to seawater is correlated with increased levels of which two proteins? 13. Give two examples of different physiological states that could confuse your interpretation of measurements of a variable like basal metabolic rate. How would you be confused? 14. What is the equilibrium potential (E x ) for an imaginary ion X 2- given the following information: [X 2- ] outside = 120 mm and [X 2- ] inside = 20 mm (please show your work). 15. What is the absolute value of the electromotive force (emf) acting on the above ion (X 2- ) if V m = -68 mv? Which way will X 2- move (in or out of the cell)?
3 Short Answer (~ 2 or 3 sentence answers; 40 points total; 4 points each) 1. How can the plasma membranes of vertebrates be modified to tolerate different thermal conditions? What molecules are involved and what properties are altered? 2. On the diagram, clearly label three phases of the action potential and indicate which ion(s) is/are primarily responsible for each of the phases identified. Label the axes with appropriate numbers and units. 3. What are the two most common electrochemical gradients established in cells? How are they established and what are two uses of these electrochemical gradients for the organism? 4. What intracellular effects does insulin binding have on most tissue cells? Under what conditions is insulin most typically released into the vertebrate blood stream? 5. What is an otolith, where is it found, and what does it do?
4 6. On the axes (which you should label) below, draw and clearly label curves that demonstrate the different responses of ion or molecule flux across the membrane as the extracellular concentration is increased for 1) a substance that freely diffuses across the membrane as compared to 2) a substance that is moved across the membrane via carrier proteins. 7. Explain how, in the cell body of a neuron, opening of ion channels for an ion whose E rev is above (closer to threshold) resting membrane potential can be termed an IPSP (inhibitory post-synaptic potential). 8. Draw and label a typical neuron. Be sure to include and label five different areas of the neuron we discussed that have different roles and physiological properties. 9. Explain the difference between relative and absolute refractory periods at the level of the membrane potential and ion channels. 10. Explain how metabolism, especially ATP production, and entropy are conceptually linked.
5 CHOOSE ONE! Essay Answer (12.5 pts; well-organized paragraphs and diagrams). Diagram and describe the transduction of sound waves into action potentials in the mammalian ear. Discussion of morphological structures at many levels and their functions will help you receive full credit. Also, briefly discuss how lateral lines on frogs and fishes are similar in structure and function to parts of the mammalian ear. OR Explain the transduction of light into electrical signals from the point of photons hitting the cornea up to the point where signals are sent toward the brain from the rods and cones. Please be sure to touch on the following topics in your discussion: anatomy, acuity, sensitivity, membrane potential, light refraction, 2 nd messenger cascades and relevant proteins, etc. Diagrams may be used to help illustrate your description. In your answer please also be sure to explain the mechanism behind photopigment bleaching.