Problem Set 1 Q&A

Problem Set 1 Q&A - Problem Set 1 Cellular...

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Problem Set 1 Cellular Neurobiology Fall 2008 1. Action potentials: a). List 5 general characteristics of action potentials. 1). The AP has a threshold (the unit is in voltage). So when the electric potential reaches threshold, the AP fires. 2). The AP is all-or-none. If potential does not reach threshold, no AP. If it reaches threshold, AP occurs or fires. 3). Information is carried in a digital code, and the strength of the stimulus is coded in the form of AP frequency. 4). The rate of change of membrane potential depends on the stimulus strength (or the speed of depolarization). The larger the stimulus the faster the rate of change in membrane potential. 5). Refractory period: time during which the cell is not excitable or difficult to excite. Absolute refractory period is 1-2 ms so during this period the neuron cannot be excited no matter what happens. The relative refractory period is 3-5 ms; during this period the neuron can be excited but it’s hard to do so. b). In section, your TA thinks that stimulating a neuron with a large stimulus will cause an action potential with a large amplitude, and stimululation with a small stimulus will generate an action potential with a small amplitude. Explain why this is not correct. The amplitude of an action potential is independent of the amount of current which produced it. In other words, a larger stimulus does not generate larger action potentials. Therefore action potentials are said to be all-or-none, since they either occur fully or they do not occur at all. Instead, the frequency of action potentials is what encodes the intensity of a stimulus. 2. Briefly explain the following terms and indicate what they are used for: a). RNA probe: b). Reduced silver stain c). Antibodies d). Voltage-sensitive dye e). Intracellular recording f). Colchicine a). RNA probes target RNA by recognizing and binding to complementary RNA sequence. These probes can be used to visualize the location of RNA. b). Reduced silver stain (Golgi stain) stains the entirety of a neuron and allows visualization of its morphology. c). Antibodies bind to specific proteins to allow visualization d). Voltage-sensitive dyes will change emission wavelength when there’s a voltage change. It can be used to study large changes in membrane potential, i.e. action potentials.
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e). Intracellular recording measures the transmembrane potential of a neuron. It can be used to study resting potentials, action potentials, synaptic potentials and sensory (generator) potentials. . f). Colchicine breaks down microtubules. One can use it to distinguishe the
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Problem Set 1 Q&A - Problem Set 1 Cellular...

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