Log in
Biology
1
answer
0
watching
476
views

Why does changing concentrations of ions change equilibrium potential and changing permeability affect threshold? You might want to discuss the Nernst Equation vs the Goldman equation.

Watch
1
answer
0
watching
476
views

For unlimited access to Homework Help, a Homework+ subscription is required.

Lelia Lubowitz
Lelia LubowitzLv2
28 Sep 2019

Unlock all answers

Get 1 free homework help answer.
Already have an account? Log in
Share

Related textbook solutions

Molecular Cell Biology
8 Edition,
Lodish
ISBN: 9781464183393
Biology: Science for Life with Physiology
6 Edition,
Belk
ISBN: 9780134555430
Concepts of Biology
OER Edition,
Openstax
ISBN: 9781938168116
Biology
2nd Edition, 2013
Openstax
ISBN: 9781947172517
Essentials of Biology
5 Edition,
Mader
ISBN: 9781259660269

Related questions

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?

Many ion channels are not normally open but must be gated oropened by some event. Which of the following is NOT a typical meansof opening ion channels?

Select one:

a. Binding of neurotransmitter to external binding site

b. Change in voltage across the membrane

c. Enzymatic reactions

d. Phosphorylation by an intracellular second messenger

Summation of local potentials can lead to a(n) _______ at theaxon hillock if the _______ is reached.

Select one:

a. equilibrium potential; threshold

b. local potential; equilibrium potential

c. action potential; equilibrium potential

d. action potential; threshold

The Na+/K+ pump helps to maintain the _______ by moving threeNa+ ions in and two K+ ions out of the cell.

Select one:

a. action potential

b. resting membrane potential

c. threshold

d. local potential

This is the peak depolarization in an action potential. At this point in an action potential two events start to happen.

1. Na+ channels begin to inactivate, which is equivalent to closing.

2. A majority of the K+ channels are beginning to open.

Determine what happens to the membrane potential when voltage-gated K+ channels are open simultaneously with voltage-gated Na+ channels (and the leak K+ channels which are still open). Increase the membrane permeability to K+ by increasing it to 115.

i. What happens to the membrane potential Em? __________________________

j. Why does the membrane potential change in this direction? __________________________ Now inactivate the voltage-gated Na+ channels by reducing the membrane permeability for Na+ back to 1. k. What is the new membrane potential? _____________

l. Is the new membrane potential less negative or more negative than the resting membrane potential listed in line รขย€ย˜bรขย€ย™ of this section? _____________

m. Why? (hint: what 2 types of K+ channels are open now?) n. Under the current ionic concentrations given, what is the most negative value that the membrane potential could reach? _____________ (Increase the permeability of the membrane to K+ to confirm your answer.)

o. What equilibrium potential has the same value? _____________

p. At this point in the action potential, when the membrane potential is more negative than the resting potential, the membrane potential is said to be hyperpolarized. What happens to voltage-gated K+ channels (membrane permeability to K+) to bring the membrane potential back to its resting potential near -70mV?_____________

When the membrane potential became more negative than the Threshold potential, the inactivated voltage-gated Na+ channels became reactivated. After the voltage-gated K+ channels closed to enable the membrane potential to return to resting membrane potential they became ready to open again. Both channels are ready to open again in order to fire another action potentia

Weekly leaderboard

Home
Homework Help 3,900,000
Biology 460,000
Start filling in the gaps now
Log in