ANP 1105 Lecture : Cellular Physiology of Nerve and Muscle.doc

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ceriseshark335

24 Mar 2012

School

University of Ottawa

Department

Anatomy and Physiology

Course

ANP 1105

Professor

Jacqueline Carnegie

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Document Summary

Flexible; defines the extent of the cell and separates the intracellular fluid from the extracellular fluid (interstitial fluid) Synonymous with cell membrane fluid mosaic model- depicts the plasma membrane as a thin structure composed of a bilayer of lipid molecules with protein molecules dispersed in it. It is fluid because it is constantly changing its shape and patter. It is a mosaic because it contains different proteins, lipid molecules etc. The lipid bilayer is constructed of phospholipids, with small amounts of cholesterol and glycolipids. Each phospholipid molecule has a polar head that is charged and is hydrophilic (water- loving) and an uncharged, non polar tail that is made of two fatty acid chains and is hydrophobic (water-fearing) 2 fatty acids attached to glycerol and phosphate group on the 3rd position. The polar heads attach to water which is the main component of inter and extracellular fluids.

Related Questions

Above is a schematic representation of a neuron with a synapse.Switch A is a synapse. R1 and R3 are the resistances of theextracellular space 2 microns from the plasma membrane. R2 is theextracellular resistance 1 mm from the plasma membrane. R5 is theintracellular resistance. When switch A is closed (synapseactivated) draw: (1) the direction of current flow in the circuit;(2) the polarity of potential changes across resistors R1-R6. (3)What are the relative magnitudes and polarities of theextracellular field potentials produced by the synaptic responserecorded at R1 and R3?

Membrane Capacitance and Conductance. For cells having simplemorphological shapes, the
intracellular voltage is nearly uniform throughout the cell suchthat any change in the membrane
potential acts equally on all parts of the membrane. If wehyperpolarize the cell or chemically block
excitable ionic conductances, the membrane potential vm ispassively related to the incoming current i
by:
Cm
dvm
dt
+Gm (vm - El ) = i (1)
where Cm is the whole-cell membrane capacitance, Gm is thewhole-cell membrane conductance, and
El is the leak potential. Most biological membranes have acapacitance of about 1 ÂµF per square
centimeter of membrane area, which allows one estimate cell size bymeasuring capacitance.
a) One way to measure the capacitance is to inject a sinusoidalcurrent i = Ie j?t and to measure the
sinusoidal perturbation in the membrane potential vm = Ve j?t . Inthe frequency domain, both the
current I and the voltage V are complex-valued numbers. Derive aformula for the cell capacitance in
terms of I and V.
b) Another way to measure cell capacitance and conductance is touse a step current injection. In this
case, the current is suddenly increased to a constant i = Io andthe voltage responds with an exponential
form. Measurement of the voltage for a known current impulseprovides a means to estimate the
capacitance and conductance. Toward this aim, find the solution ofEq. 1 for a step increase in
current. Once you have this solution, how would you use the voltageand current measurements to
estimate the passive capacitance and conductance?

It is not possible to see very small objects, such as viruses,using an ordinary light microscope. An electron microscope can viewsuch objects using an electron beam instead of a light beam.Electron microscopy has proved invaluable for investigations ofviruses, cell membranes and subcellular structures, bacterialsurfaces, visual receptors, chloroplasts, and the contractileproperties of muscles. The "lenses" of an electron microscopeconsist of electric and magnetic fields that control the electronbeam.

As an example of the manipulation of an electron beam, consider anelectron traveling away from the origin along the x axis in the xyplane with initial velocity v = vi. As it passes through the regionx = 0 to x = d, the electron experiences acceleration a = ax + ay,where ax and ay are constants. For the case vi = 1.77 107 m/s, ax =7.35 1014 m/s2, and ay = 1.45 1015 m/s2, determine the following,at x = d = 0.0100 m.
(a) the position of the electron
yf =__________ m
(b) the velocity of the electron
vf =________ m/s +__________ m/s
(c) the speed of the electron
|vf| =___________ m/s
(d) the direction of travel of the electron (i.e. the angle betweenits velocity and the x axis)
=________ Â°

ANP 1105 Lecture : Cellular Physiology of Nerve and Muscle.doc

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