417final - BME 417 Final Exam 1) Axon All-or-nothing The...

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1 BME 417 Final Exam 1) Axon Wire All-or-nothing The axon’s conduction of AP is like digital signal, the information can only be coded by frequency. Graded The wire’s conduction can be analog. The information can be coded by both amplitude and frequency. No-loss conduction As AP propogates along an axon, its amplitude does not decrease over distance. Degrade over distance When signal propagates along a wire, its amplitude decreases over distance. Max freq When coding for information, there’s maximum frequency of AP an axon can carry. This is due to the refractory period that accompanies every AP. No max freq There’s no maximum frequency that a wire can carry. In absolute term, there is, however, it’s many order of magnitudes above that of the axon. Charge carrier move to signal While the AP travel down the axon membrane, the charge carrier actually just move across the membrane. Charge carrier move // to signal In a wire, the direction of charge carrier movement is parallel to the direction of signal propagation. Ion as charge carrier Sodium and potassium ions are the primary charge carrier for AP propagation along an axon. Electron as charge carrier (metal wire) Free electrons are the primary charge carrier for signal propagation along a metal wire.
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2 3a) From the graph, we read the following: Primary Secondary Initial Gain 90 5 Cornering Freq 1 c/s 1 c/s Slope after cornering 20dB/decade 20dB/decade Note that the freq in the plot is given in c/s. To convert it to rad/s, we multiply it by 2 π . In the transfer function, the initial flat line is represented by a factor of 90 and 5 respectively. The slope after the cornering freq is represented by a factor of 1+as where the cornering frequency is given by 1/a. Cornering freq = 1/a = 1 c/s = 2 π rad/s The overall transfer functions are: H primary ( s ) = 90*(1 + s 2 " ) H sec ondary ( s ) = 5*(1 + s 2 ) The corresponding phase response of the transfer functions fairly approximate that of Fig 6, time delay is not necessary. 3b) Intuitively, a stretch receptor in a cat ought to provide a lot more refined, accurate, and fast information on the muscle than a stretch receptor in a crayfish. After all, a mammal is considered more evolutionarily advanced than a crustacean. First of all, the cat’s muscle stretch receptor is broken down into two types – primary and secondary – whereas in the crayfish muscle, there is only one type of stretch receptor. This means that there can be a distribution of function in the cat’s stretch receptor. In fact, the primary receptor is specialized to sense the velocity of movement whereas the secondary receptor is specialized to sense the position of the muscle. There’s no such luxury for a crayfish, so both measurement need to be accomplished by a single receptor. Once again, intuitively, the specialization of receptor should allow for either greater
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This note was uploaded on 04/30/2008 for the course BIOMEDE 417 taught by Professor Cain during the Winter '07 term at University of Michigan.

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417final - BME 417 Final Exam 1) Axon All-or-nothing The...

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