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Compare the intracellular and extracellularconcentrations for Na and K of a %u201Cgeneral%u201D mammalian cellto that in a squid which lives in the salty ocean. What are thevalues for Na and K out and in? (You can find values by going togoogle and typing in %u201Csquid axon ion concentrations%u201D orgoing to http://faculty.weber.edu/nokazaki/Comparative%20Animal%20Physiology/Tests/Chp%2011%20Essay%20questions.htm). Why are they different? Why is the voltage ofthe squid neuron so very similar to that of a %u201Cgeneral%u201Dmammalian cell (hint: is it the absolute concentrations of ionsthat are important or their ratios across the plasma membrane)?

You will be plotting the flowof ions -
which is an electrical current. When you make yourplots, the y axis
will be the amount of current flow. Make it sothat inward current
(that is, net flow of ions into the cell) isdownward (below zero), and
outward current (that is, the flow of ions out ofa cell) is positive.




Then, Use the Goldman equation and the Goldmanequation simulator to answer the following questions. Whenanswering "Why" questions, do so in one-two sentences.


Start with the default conditions in thesimulator.

PK = 100 Ko = 10mM Ki = 100

PNa =1 Nao =100 Nai = 1

PCl =10 Clo= 100 Cli = 10

What is the voltage of a cell that has thesevalues? Why

If the relative potassium permeability waschanged to 1, what would be the voltage of the cell? Why?

Change the permeability of K back to 100. Ifthe permeability to chloride is changed from 10 to 100, will therebe a voltage change? Why?

Change the permeability of chloride back to10. Now, change the extracellular concentration of potassium to 90mM. What is the voltage of the cell? Why?

Now change the extracellular concentration ofpotassium to 200. What is the voltage of the cell? Why? Now changethe permeability to potassium to 9999. Is there a further largechange in the voltage of the cell? Why?

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Irving Heathcote
Irving HeathcoteLv2
28 Sep 2019

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Related questions

Studies on the squid giant axon were instrumental to our current understanding of how action potentials are generated. You decide to do some experiments on the squid giant axon yourself.

A. You remove the cytoplasm in an axon and replace it with an artificial cytoplasm that contains twice the normal concentration of K+ by adding KOAc, where OAcรขย€ย“ is an anion to which the membrane is impermeable. In this way, you double the internal concentration of K+ while maintaining the bulk electrical balance of the cytoplasmic solution. Will this make the resting potential of the membrane more or less negative?

B. You add NaCl to the extracellular fluid and effectively double the amount of extracellular Na+ ions. How does this affect the action potential?

C. You replace half of the NaCl in the extracellular fluid with choline chloride. (Choline is a monovalent cation much larger than Na+. Note that the presence of choline will not impede the flow of Na+ through its channels.) How will this affect the action potential?

Studies on the squid giant axon were instrumental to our current understanding of how action potentials are generated. You decide to do some experiments on the squid giant axon yourself.

A. You remove the cytoplasm in an axon and replace it with an artificial cytoplasm that contains twice the normal concentration of K+ by adding KOAc, where OAcรขย€ย“ is an anion to which the membrane is impermeable. In this way, you double the internal concentration of K+ while maintaining the bulk electrical balance of the cytoplasmic solution. Will this make the resting potential of the membrane more or less negative?

B. You add NaCl to the extracellular fluid and effectively double the amount of extracellular Na+ ions. How does this affect the action potential?

C. You replace half of the NaCl in the extracellular fluid with choline chloride. (Choline is a monovalent cation much larger than Na+. Note that the presence of choline will not impede the flow of Na+ through its channels.) How will this affect the action potential?

1)What type of cell allows the immune system to respond morequickly if the same antigen is encountered a second time?

A)leukocytes

B)memory cells

C)macrophages

D)neutrophils

E)natual killer cells

2)why is the heart divided funtionally into two separate pumpsthat work in series?

A)because arteries carry blood away from the pump and veinsbring blood back to the pump

B)because blood decreases in pressure as it travels throughcirculation

C)because vessles in the vasculature keep blood moving in onedirection'

D)because there are four chambers to the heart

E)none of the above-the heart contracts in unison and is notdivided into two pumps

3)which of the following statements is correct?

A)Na+,K+, Ca2+ and Cl- are all more concentrated in theEXTRACELLULAR fluid

B)Na+, K+, Ca2+ and Cl- are all more concentrated in theEXTRACELLULAR fluid

C)Na+, Ca2+, and Cl- are all more concentrated in theEXTRACELLULAR fluid

D)K+, ca2+ are more concentrated in the EXTRACELLULAR fluid

E)K+, Ca2+ are more concentrated in the EXTRACELLULAR fluid

3)During skeletal muscle contraction:

A)the width of the H-zone decreases

B)the actin heads bind to myosin chain

C)ATP hydrolysis requires Ca2+ as a cofactor

D)tropomyosin changes conformation when Ca2+ binds

E)all of the above occur during skeletal muscle contraction

4)The rapid depolarization phase of myocardial contratile cellaction potential is due to the movement of which ion(s)?

A)Ca2+ flows into the cytosol

B)K+ flow out of the cytosol

C)Na+ flow into the cytosol

D)Ca2+ flow out of the cytosol

E)K+ flow into the cytosol

5)You are a physiology graduate student asked to study theeffect of ion permeability on the initiation of action potentials.You have isolated a cell with resting membrane potential of -70mVand have determined that the cell's threshold voltage is -55mV. Youthen change the cell to make it less permeable to K+ ions(Eions=-90mV)

With all ther condition staying the same, has cell's restingmembrane potential been DEPOLARIZED or HYPERPOLARIZED; and will thecell require a greater or smaller stimulus to reach threshold?

A)hyperpolarize; smaller

B)depolarize;greater

C)hyperpolarize;greater

D)depolarized; smaller

E)none of the above answers are possibe

6)Skeletal muscle cells are UNUSUAL in that they :

A)lack smooth endoplasmic reticulum

B)have no mitochondria

C)depend entirley on anaerobic respiration

D)have MULTIPLE nuclei

E)none of the baove are found in the skeletal muscle cells

7)What is the name for the autonomic nervous system synapses atthe neuroeffector?

A)electrical synapses

B)axon viscosities

C)bidirectional synapses

D)axon varicosities

E)light bulb synapse

8)Which cytokines are involvedin making cells resistant toviruses?

A)colony-stimulating actors

B)interferons

C)erythrpoietin

D)major histocompatibility complex

E)none of the above can make a cell resistant to a virus

9)If a person switiches from normal breathing to more shallowbreathing, whcih statement is true

A)tidal volume decreases

B)alveolar PO2 decreases

C)alveolar ventilation decreases

D)"a" and "b"

E)"a", "b', and "c"

10)Which scenerio supports hyperpolarization of pre-synapticcell?

A)allowing Cl- ions into the cell

B)allowing K+ ions to leave the cell

C)allowing Ca2+ ions into the cell

D)"a" and "b"

E)"a", "b", and "c"

11)The gap junctions in cardia muscle are part of specializedcell junctions that are localized to the__________.

A)transverse tubules

B)intercalated discs

C)Interdigitated fingers

D)desmosomes

E)high-end shppoinf malls

12)What role does myosin light chain kinase (MLCK) play insmooth muscle cell contraction?

A)dephosphorylates myosin

B)phosphorylates actin

C)phosphoylates myosin

D)dephosphorylates actin

E)both "a" and "c"Given that your forearm is 30cm long and yourbiceps inserts 2 cm away from your elbow joint, how much force mustyour biceps exert to hold up a 10kg weight?

A)0.67kg

B)6.0kg

C)20kg

d)150kg

e)600kg

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