HUMB1000 Lecture Notes - Lecture 11: Action Potential, Membrane Potential, Neurotransmitter

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beigemarten277

3 Aug 2018

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Electrically neutral= positive and negative ions balance each other out: permeability of the cell membrane to ions. Non-gated ion channels: also known as (cid:494)leak(cid:495) ion channels, ion specific, cell membrane has more k+ leak ion channels compared to na+ leak ion channels. Gated ion channels require signals to open them (1) ligand-gated ion channel-open when chemical binds (2) voltage-gated ion channel-open in response to change in electrical charge (3) other-gated ion channel-open to touching, change in temp, change in pressure. Resting membrane potential: resting membrane potential the difference in charge across the cell membrane in a resting cell. Rmp of neurons = - 70 mv where the negative sign indicates the charge on the intracellular side of the cell: rmp caused by leak ion channels and the na+/k+ pump. Pink=sodium (fewer sodium leak ion channels that enter cell) Purple=potassium (more potassium leak ions that exit cell) Orange= sodium potassium pump (bring in 2 k and sends out 3 na2)

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In order for Neurons to communicate, Resting Membrane Potential must CHANGE. Examples of changes in Membrane Potential included Graded Potentials and Action Potentials. In order for there to be a change in membrane potential, ions must move across the plasma membrane. There are THREE Primary types of Ion Channels: Passive (Leak) Channels, Voltage-gated Channels and Chemically-gated Channels.

DIRECTIONS

Indicate which voltage-gated channels are functioning during each phase of an Action Potential

skyhorse437

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

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

ochremouse799

HUMB1000 Lecture Notes - Lecture 11: Action Potential, Membrane Potential, Neurotransmitter

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