15

Question 1

Electrical signals in neurons occur?

Answer 1

In all parts of the neuron. Graded potential in the cell body, action potential in the axons, and synaptic potential at the synapse of the neuron.

Question 2

What potentials result in the changes in membrane potential?

Answer 2

Graded potential, action potential, and synaptic potential

Question 3

When measuring membrane potential, what do you expect? 2•

Answer 3

•Always reported as charge inside relative to charge outside
•In both animals and plants, the inside of the cell is more negative than the outside.

Question 4

Does the entire cell have a charge difference?

Answer 4

No, only the surfaces of the membrane.

Question 5

Equilibrium potential?

Answer 5

Membrane potential where the electrochemical gradient between the two ions balance out.

Question 6

Once equilibrium potential is reached, what happens to the movement of the ions?

Answer 6

They stop moving.

Question 7

If the membrane potential gets lower than the equilibrium potential, then what is the movement of the ion that has its channel open?

Answer 7

It goes against its concentration gradient.

Question 8

What manages the concentration gradient in neurons?

Answer 8

The sodium potassium pump (NA+/K+ - ATPase). This ensures that ions don’t flow in the wrong direction.

3Na+ leaves the cell for every 2K+ that enters the cell.

Question 9

Can you use equilibrium potential to predict the direction in which an ion will move?

Answer 9

Yes by comparing it to membrane potential.

Question 10

Sodium is trying to get the cell to?

Answer 10

+62 mV

Question 11

Potassium is trying to get the cell to?

Answer 11

-90 mV

Question 12

Why is the membrane resting membrane potential closer to K+ equilibrium potential?

Answer 12

Because K+ is more permeable than Na+.

Question 13

If you have several ion channels open, what determines membrane potential?

Answer 13

A weighted average based on permeability.

Question 14

The importance of permeability in setting membrane potential is for mixed in the?

Answer 14

Goldman-Hodgkin-Katz constant field equation (GHK).

Question 15

GHK = ______ equation if one of three ion channels are open?

Answer 15

Nrest equation.

Question 16

Why do we only consider Na+, K+, and Cl- in GHK equation?

Answer 16

Because permeability in other ions are so low.

Question 17

What causes changes in membrane potential?

Answer 17

Changes in membrane permeability.

Question 18

Gated ion channels?

Answer 18

Those that can open and close

Question 19

Leak channels?

Answer 19

Those that are always open

Question 20

What causes gated channels to open and close, and how?

Answer 20

By a signal which switches a protein gate that blocks the channel (pore).

Question 21

How does the signaling process work in ion gated channels?

Answer 21

Sensory receptor gets a stimulus, and changes the conformation of the receptor. This receptor could be a channel itself, or it signals to a channel.

Question 22

What type of potential is caused by neurotransmitters binding to a receptor?

Answer 22

A graded potential.

Question 23

What changes the frequency of signals?

Answer 23

How much of a membrane potential change occurs by opening more ion graded channels.

Question 24

Steps of graded potential from neurotransmitter?

Answer 24

•Neurotransmitter binds to a ligand-gated Na+ channel
•Na+ enters the cell through the open channel
•Current spreads through the cell
•The strength of the signal decreases with distance.

Question 25

Why do signals die out eventually when moving through the cell?

Answer 25

Because of Intracellular resistance

Question 26

How do you get an action potential?

Answer 26

They are triggered by a graded potential by dendrites and cell body. It alter membrane potential in the axon hillock (trigger zone) and results in an action potential in the axon.

Question 27

Action potentials are triggered when?

Answer 27

Potential exceeds the threshold potential at the “trigger zone” of the neuron.

Question 28

Spatial summation?

Answer 28

Graded potentials originate at different locations and can influence the net change in Vm. This can allow neuron to reach threshold.

Question 29

Temporal summation?

Answer 29

The time of graded potentials.

Question 30

Action potential Phases for membrane potential? 3•

Answer 30

•depolarization phase (less negative rapidly)
•Repolarization Phase (more negative rapidly)
•Hyperpolarization phase (more negative than resting membrane potential, and then back to resting membrane potential)

Question 31

During hyperpolarization, what ion channels are open and closed?

Answer 31

Potassium channels are open and sodium channels are closed.

Question 32

Feedback loop of neuron membrane potential?

Answer 32

Sodium channels are initially closed, but then opens and sodium goes to its equilibrium potential. This causes neighbouring sodium channels to open, which causes more depolarization, and a greater change of permeability.

Question 33

If there is a higher density of voltage gated Na+ channels, then how does action potential threshold change?

Answer 33

Lower threshold required to trigger an action potential since the channels are close enough to be opened from the feedback. Graded potentials can travel in longer distances.

Question 34

!!!!How to stop membrane potential feedback cycle?

Answer 34

There are two gates in the ion gated channel. The activation gate closes the channel. When there is a graded potential, the activation gate opens and the inactivation gate is also open, which cause rapid flow of Sodium. But over time, the inactivation gate starts to close to slow Na+ diffusion.

Question 35

Excitatory postsynaptic potential (EPSP)?

Answer 35

Contribute to depolarization.

Question 36

Inhibitory postsynaptic potential? (IPSP)

Answer 36

Contributes to hyperpolarization