Neurobiology Midterm Review: Practice Questions, Exams of Biology

Download Neurobiology Midterm Review: Practice Questions and more Exams Biology in PDF only on Docsity! Practice Midterm #2 Questions BILD 2 8/21/08 1) Action potentials originate at the ___axon hillock__ , travel down axons, and terminate at ___ a synaptic terminal___. 2) _Glia_ cells support and nourish neurons. 3) The so called “fight or flight” response is triggered by activation of the __sympathetic__ division of the autonomic nervous system, and this leads to _increased heart rate, etc.__ (one specific physiological response). When we need to “rest and digest”, the __parasympathetic_ division of the autonomic nervous system is activated. 4) The olfactory receptors that bind to specific odorant molecules belong to a specific class of transmembrane protein receptors called _G-protein coupled receptors__. They are named this because they communicate directly with intracellular signal transduction proteins called _G proteins_. 5) When a woman becomes pregnant, at least two major events that normally occur monthly in her reproductive cycle need to be halted. What are these events? What set of signal(s) ensure that these events are halted? She needs to not shed the endometrium (menstruate), and she needs to stop ovulating. The hormone hCG, secreted by the embryo, acts like LH to prevent degeneration of the corpus luteum. The corpus luteum will thus continue to secrete estrogens and progesterone. These steroid hormones will then act on the uterus to maintain the endometrium and allow formation of the placenta, and they will act on the hypothalamus to prevent release of GnRH. GnRH must be released to allow growth and maturation of follicles, and ovulation. 6) Sodium (Na+) is kept at a concentration of 150 mM outside a mammalian neuron, and 15 mM inside. What would happen if you were recording the electrical activity of this neuron (stimulating it and recording action potentials) while you varied the Na+ concentration outside the neuron downwards or upwards from 150 mM? What would happen to the resting potential of the neuron? If the Na+ concentration outside is raised above 150 mM, it will alter the action potential peak upwards, because the Na+ equilibrium potential will be more positive. However, voltage gated Na+ channels will still close too rapidly to allow the peak of the action potential to reach the new Na+ equilibrium potential (just as in a normal action potential). The membrane will depolarize more rapidly. If the Na+ concentration outside is decreased much below 150 mM, the peak of the action potential will be decreased below the approximately +35 mV that is normal for a mammalian neuron. This is because the equilibrium potential for Na+ will have been decreased below this level. The membrane will also depolarize more slowly. The resting potential will not change significantly if the Na+ concentration is changed outside the neuron, because the resting potential is determined mostly by the concentration differences of K+ ions across the membrane and the flow of K+ ions. 7) After a car accident, a patient has no apparent cognitive dysfunctions, but has trouble walking – maintaining balance. What region(s) of his brain might have been damaged? How might you confirm this? The cerebellum coordinates movement and balance, so it might have been damaged. You’d want to know, for example, if the patient had suffered damage to the back of his head, since that is where the cerebellum is located in the skull. However, these symptoms could also be due to damage to the inner ear, since this is the organ that sends sensory information relating to balance to the brain. If the inner ear was damaged, you might expect hearing loss from that ear (and the damage would have been to the side of the head). If the cerebellum was damaged, the patient would probably also have trouble with hand-eye coordination. 8) How is the resting potential of a neuron established? What are the major protein components in a neuron’s plasma membrane that serve to establish and maintain the resting potential? Differences in ion concentrations have to be established across the membrane at first; this is accomplished by the Na+/K+ ATPase. Then, some ions must be allowed to pass through the membrane while others are prevented from passing. The Nernst equation can be used to predict what the membrane potential should be when the concentrations of ions are known, and their relative permeabilities, across a membrane. Since at rest, the membrane is only very permeable to K+, the membrane resting potential is close to the K+ equilibrium potential. (K+ leak channels – K+ channels open)