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BIO Signals in nerve cells stimulate muscles The input end of a human nerve cell is connected to an output end by a long, thin, cylindrical axon. A signal at the input end is caused by a stretch sensor, a temperature sensor, contact with another cell or nerve or some other stimulus. At the output end, the nerve signal can stimulate a muscle cell to perform a function (to contract provide information to the brain etc).
The axon of a so-called unmyelinated human nerve cell has a radius of
When an external source stimulates the input end of the nerve cell so the potential inside reaches about -50 mV, gates or channels in the membrane walls near that input open and sodium ions rush into the axon. This simulates neighboring gates to swing open and sodium ions rush into the axon farther along. This disturbance quickly travels along the axon—a nerve impulse. The potential across the inside of the membrane changes in 0.5 ms from 70 mV to + 30 mV relative to the outside. Immediately after this depolarization potassium ion gates open and positively charged potassium ions rush out of the axon, repolarizing the axon. Sodium and potassium ion pumps then return the axon and its membrane to their original configuration.
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Chapter 19 Solutions
College Physics
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- The speed of propagation of the action potential (an electrical signal) in a nerve cell depends (inversely) on the diameter of the axon (nerve fiber). If the nerve cell connecting the spinal cord to your feet is 1.1 m long, and the nerve impulse speed is 18 m/s, how long does it take for the nerve signal to travel this distance?arrow_forwardignment Score: 44.7% estion 9 of 11 > Find the total capacitance Ctot of the combination of capacitors shown in the figure, where C₁ = 5.15 μF, C₂ =3.55 μF, C3 = 5.25 μF, C4 = 2.75 μF, Cs = 0.750 μF, and C6 = 15.0 μF. 3 Clot = TOOLS Questio x10 Physics 14 $ 5 978 Λ ◊ 1 6 HF MacBook Pro & 7 28 E R T Y U D F G H Resources Ch Cx Give Up? Hint * ∞ ( ) 8 9 0 - о J K L C V B N M P Att + 11 יו V ?arrow_forwardIntegrated Concepts (a) Referring to Figure 20.34, find the time systolic pressure lags behind the middle of the QRS complex, (b) Discuss the reasons for the lime lag. Figure 20.34 A lead II ECG with corresponding arterial blood pressure. The QRS complex is created by the depolarization and contraction of the ventricles and is followed shortly by the maximum or systolic blood pressure. See text for further description.arrow_forward
- Integrated Concepts Use the ECG in Figure 20.34 to determine the heart rate in beats per minute assuming a constant time between beats. Figure 20.34 A lead II ECG with corresponding arterial blood pressure. The QRS complex is created by the depolarization and contraction of the ventricles and is followed shortly by the maximum or systolic blood pressure. See text for further description.arrow_forwardDefine depolarization, repolarization, and the action potential.arrow_forwardTry to complete Table P26.4 from memory. If you must look back in this chapter or other chapters for information, note the page number, figure number, or equation number that helped you. TABLE P26.4arrow_forward
- Some physical systems possessing capacitance continuously distributed over space can be modeled as an infinite array of discrete circuit elements. Examples are a microwave waveguide and the axon of a nerve cell. To practice analysis of an infinite array, determine the equivalent capacitance C between terminals X and Y of the infinite set of capacitors represented in Figure P25.47. Each capacitor has capacitance C0. Suggestions: Imagine that the ladder is cut at the line AB and note that the equivalent capacitance of the infinite section to the right of AB is also C.arrow_forward2. A simplified model of an axon based on a simple RC circuit is shown below. Consider an incremental length of 5 x 10-10 m non-myelinated segment of an axon whose properties are listed in the table below. A potential of 80 mV is maintained at point a. a. How many discrete segments make up a distance of 0.01 mm? b. What is the voltage at a point 0.01 mm away from a? a | R. Rm RT R Values Property Axon Radius 5 x 10marrow_forwardJ09arrow_forward
- 1. BRANCHING BLOOD VESSELS Figure 1: A Picture of Blood Capillaries The blood vascular system consists of blood vessels (arteries, arterioles, capillaries, and veins) that convey blood from the heart to the organs and back to the heart. This system should work so as to minimize the energy expended by the heart in pumping the blood. In particular, this energy is reduced when the resistance of the blood is lowered. One of Poiseuille's Laws gives the resistance R of the blood by the following equation: R = C where L is the length of the blood vessel, r is the radius, and C is a positive constant determined by the viscosity of the blood. Figure 2: Vascular Branching Sketch 1 Answer the following questions: (a) Looking at Figure 2, express the total resistance R given by Equation 1 of the blood along the path ABC as a function of the branching angle 0. Meaning that, you need to find the following equation: + CBC| R(0) = C where length |AB| and the length |BC| of the blood vessel are written…arrow_forward8. Given a set of capacitors: 7 nF, 6 nF, 5 nF, 4 uF, 3 pF and 10 µF, solve the following problems: a. Solve the total capacitance for a parallel circuit and illustrate the circuit. b. If the parallel circuit is connected to a 60V battery, find the total charge. C. Given the same voltage, solve for the energy.arrow_forwardcapacitancearrow_forward
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