BIOL 111 Lecture Notes - Lecture 7: Radula, Terrestrial Mollusc, Saltatory Conduction

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May be gated (have the ability to open or close depending on changes in voltage or whether certain chemicals bind to it or not) ion pumps: Moves ions against their chemical gradient energy (atp) is required active transport occurs sodium-potassium pump (atpase) Membrane proteins are selective (a protein will only be activate by certain ions and molecules) certain k+ channels are always open so k+ is constantly diffusing out of the cell voltage-gated na+ channels open when voltage difference changes. Membrane potential is at resting potential (-60 mv) the k+ channel is opened and the voltage-gated channels are closed. 2. stimulus occurs this causes na+ channels to open na+ leak into the cell the interior of the cell gets more positive (slight depolarization) 3. if stimulus is big enough (membrane potential must be raised above threshold potential, More na+ channel open action potential: na+ channels start to close and k+ channels open.

Related Questions

Consider a typical cell at its resting membrane potential (rest Vm). The membrane temporarily becomes more permeable to Cl-.

Ecl = -65mV, resting Vm = -60mV

Does an electrical force (gradient) exist, if so in what direction? (.5 point)

What direction will the ion flow (said another way, what is the electrochemical gradient? (.5 point)

Would you expect the chloride equilibrium potential to change and if so, what direction will the change be? (.5 point)

If a cell were only permeable to one ion, would the Nernst potential for that ion (Ex) and the resting membrane potential be the same or different (if so how are they different)? (.5 points)

1. The plasma membrane of rod and cone cells are

a) At resting potential in the dark and deploarized in thelight

b) At resting pootential in the dark and hyperpolarized in thelight

c) Depolarized in the dark and hyperpolarized in the light

d) Hyperpolarized in the dark and at resting potential in thelight

e) Hyperpolarized in the dark and depolarized in the light

2. The equilibrium potential of K+ ions in nerve cells is about-90mV. The membrane potential of a typical nerve cells at rist is-70mV. Therfore

a) Increasing the permeability of a resting neuronal membrane toK+ ions will increase the membrane potential (that is, make it morenegative, inside with respcect to outside)

b) In nerve cells at rest, there is a net diffusion of K+ ionsout of the cell

c) Increasing the membrane potential of a nerve cell would slowthe diffusion of K+ ions out of it.

d) K+ is not the only ion that is permeable at rest

e) All of the above

3. Which of the following is responsible for the replarizingphase of the action potential?

a) Voltage-gated Na+ channels are opened.

b) The Na+-K+ pump restores the ions to theri original restingstate.

c) The permeability to Na+ increases greatly.

d) ATPase destroys the energy supply that was maintaining theaction potential at its peak.

e) The permeability to K+ increases greatly while that to Na+decreases

4. The Relative refractory period of an axonm conincides withthe period of

a) Activation and inactivatioin of voltage-gated Na+channels

b) Increased Na+ flux into the cell

c) Increased K+ flux into the cell

d) Increased K+ flux out of the cell

e) Increased Na+ flux out of the cell

5. The plasma membranes of rod and cone cells are

a) At resting potential in the dark and epolarized in thelight

b) At resting potential in the dark and hyperpolarized in thelight

c) Depolarized in the dark and hyperoplarized in the light

d) Hyperpolarized in the dark and tat resing potential in thelight

e) Hyperpolarized in the dark and depolarized in the light

I need help answering this question:

Observation: A strange deep sea creature has been discovered. You are recording from a neuron in itâs brain with an electrode. Upon electrical stimulation, you observe change in voltage that resembles an action potential: the voltage rises, shoots up when it crosses a threshold, and then rapidly falls back to resting potential. Looking at the ions inside and outside the cell, you find that there is a high concentration of positively charged Lithium ions outside the cell and low concentration inside the cell. There is also a high concentration of potassium ions inside and low outside. Finally, there is an equal amount of Chloride ions on both sides. Strangely enough, there arenât any Sodium ions around.

Based on these observations, you ask âIf there is no sodium, what ion is mediating the âaction potentialâ?â

In 100 words or less: 1. Formulate a hypothesis as to what ion might be mediating the action potential.2. Design an experiment to test your hypothesis. 3. State what outcome would confirm your hypothesis.

BIOL 111 Lecture Notes - Lecture 7: Radula, Terrestrial Mollusc, Saltatory Conduction

BIOL 111 Full Course Notes

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