Practice Midterm 2

Practice Midterm 2 - Practice Midterm #2 Questions BILD 2...

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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 ran membrane 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
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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
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Practice Midterm 2 - Practice Midterm #2 Questions BILD 2...

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