PHGY 210 Lecture Notes - Glutamine, Collecting Duct System, Extracellular Fluid

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magentacricket108

14 May 2012

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Potassium (k) is the most abundant intracellular ion. The k concentration in the extracellular fluid is extremely important for the function of excitable tissues (nerve and muscle). Reason: the resting membrane potentials of these tissues are directly related to the relative intracellular and extracellular k concentrations. Hyperkalemia: high concentration of k in the extracellular fluid (>5 meq/l) Hypokalemia: low concentration of k in the extracellular fluid (<3. 5 meq/l) Both cause abnormal rhythms of the heart and abnormalities of skeletal muscle contraction. Hyperkalemia is usually the most often reason for consultation, usually from an emergency room. When it becomes sinusoidal, that"s when an electrical tachycardia occurs and you must administer a shock. Fruits and nuts contain a lot of potassium so when you"re on dialysis, they could kill you! Normally, the tubules reabsorb most of this filtered k so that very little of the filtered k appear in the urine.

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?

Focal adhesions ________.

Option A: contain integrins that develop transient interactions with the extracellular matrix

Option B: collect information about the chemical properties of the extracellular environment

Option C: transmit information to the cell interior that may lead to changes in cell adhesion, proliferation or survival

Option D: all of the choices are correct

blushreindeer609

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?

PHGY 210 Lecture Notes - Glutamine, Collecting Duct System, Extracellular Fluid

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