BIOL121 Lecture Notes - Lecture 9: Depolarization, Cholinergic, Sodium-Potassium Alloy

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14 Aug 2018

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Neurons are excitable" cells: have charge across their surface and can alter that charge. Differing concentrations of the na+ and k+ ions between the inside and outside of the neuron: responsible for resting membrane potential. Channels (endings and axons) that allow movement of ions across the membrane. Intracellular fluid (cytosol) inside: passive, gated, voltage gated, transmitter (ligand) The transmembrane potential in an undisturbed cell. More sodium (na+) on the outside in the ecf. More potassium (k+) and protein ions have negative (-ve) in the icf. The different (potential) across the membrane is -70mv. Pump that returns the na+ and k+ ions that leak through the membrane: leak channels. Moves ions against the electrochemical gradient: 3 sodium ions are pushed out, 2 potassium ions are pulled in. Rapid, transient depolarisation of the cell membrane. Signal is repeated every step along the membrane; propagated. But only an axon can generate (start) one. At rest membrane -70mv, gated channels close.

Related Questions

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 âbâ 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

sapphirepanda54

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

1a. all of the following are true about nerons except... (A. they produce ATP by cellular respiration, B. they are found in the central and peripheral nervous system, C. they have Na+/K+ pumps in their membranes, D. they can rapidly depolarize, E. they don't contain nucleir or mitochondria

1b. a reesting potential of -70mV ...(A. is possible because of voltage-gated sodium channels, B. is possible because of ligand-gated sodium, C. means that the outside of the neuron is more negative than the inside, D. is an IPSP that leads to threshold potential)

1c. after an action potential is triggered, the rapid increase in membrane potential to +50mV can be attributed to (A. opening of voltage-gated sodium channels, B. reversal of the direction of the sodium/potassium pump, C. opening of voltage-gated potassium, D. closing of ligand-gated potassium channels)

BIOL121 Lecture Notes - Lecture 9: Depolarization, Cholinergic, Sodium-Potassium Alloy

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