Neurophysiology

Question 1

Communication depends on what two things?

Answer 1

1) voltage difference across the membrane

2) differential permeability

Question 2

What is differential permeability?

Answer 2

Permeability is ease with which something can cross. These changes in differential permeability are going to change over time concerning what can cross the membrane at different time periods.

Question 3

What level of mV is a Resting Membrane Potential?

Answer 3

-70 mV from inside to outside of cell

Question 4

What is a potassium leak?

Answer 4

Potassium going through a non-gated channel

Question 5

What contributes to the level of mV, -70 mV, at Resting Membrane Potential?

Answer 5

1) The Sodium-Potassium Pump: uses ATP that goes against the concentration gradient of the Neuron. 3 Na+ come out, 2 K+ come in.
2) The Potassium Leak: Potassium will move from a higher concentration to a lower concentration via a non-gated potassium channel, which is always open.
3) Large negatively proteins that are contained in the inside of the cell

Question 6

What happens when, when generating an action potential, the local potential is brought to the level of threshold?

Answer 6

Voltage-Gated Sodium Channels open.

Question 7

What level of mV is threshold at?

Answer 7

-55 mV.

Question 8

How many mV are needed to bring the local potential, at the Resting Membrane Potential, up to the level of threshold?

Answer 8

+15mV

Question 9

What happens when Voltage-Gated Sodium Channels open?

Answer 9

Sodium will pour in using the concentration gradient and depolarizing.

Question 10

What closes at +20 mV during an action potential?

Answer 10

Voltage-Gated Sodium Channels close and deactivate.

Question 11

What opens at +20 mV during an action potential?

Answer 11

Voltage-Gated Potassium Channels open.

Question 12

How is repolarization caused?

Answer 12

By potassium leaving via the Voltage-Gated Potassium Channels being open.

Question 13

Besides Voltage-Gated Potassium Channels being opened during repolarization, what else occurs, causing the potential to decrease to -90mV?

Answer 13

The Potassium Leak via the non-gated potassium channel, which is always open.

Question 14

During an action potential, what happens during repolarization when the potential gets back down to -70mV?

Answer 14

Voltage-Gated Potassium Channels are unlocked.

Question 15

Information travels along the axon via:

Answer 15

Action potentials

Question 16

How do you get another action potential to happen?

Answer 16

With a refractory period, which is a time period in which no action potential will occur

Question 17

2 kinds of Refractory Periods:

Answer 17

1) Absolute refractory period: no new action potential will happen no matter what
2) Relative refractory period: no new action potential will be generated UNLESS a greater than normal stimulus is present

Question 18

How many mV is a normal stimulus?

Answer 18

+15 mV

Question 19

If you are at a potential of -85 mV, which refractory period are you in and how much of a stimulus would be necessary in order to bring it back to threshold to start another action potential?

Answer 19

The Relative Refractory Period and a greater than normal stimulus of +30 mV is needed to get to threshold.

Question 20

What is Continuous conduction?

Answer 20

Every point along the axon is undergoing depolarization in series.

Question 21

What is saltatory conduction?

Answer 21

Depolarization only occurs at the Nodes of Ranvier, due to the presence of myelin (wrapping of the neurolymmocyte). It is quicker than continuous conduction.

Question 22

True or False: Because of Na+ pouring in during depolarization at one area of an axon, the next area will also receive some of the Na+, causing it to reach threshold and generate its own new action potential.

Answer 22

True

Question 23

Na+ pouring in during depolarization at one area of an axon, the next area will also receive some of the Na+, causing it to reach threshold and generate its own new action potential, but will not cause the previous axon to receive another action potential because of what?

Answer 23

Because the previous axon would be in the Absolute Refractory Period, during which no new action potential will happen no matter what.

Question 24

Are there gates below the myelin sheath? What disease effects the myelin sheath?

Answer 24

There are no gates below the myelin sheath. Multiple sclerosis effects the myelin sheath.

Question 25

What are three ways that you could increase conduction velocity?

Answer 25

1) Increase temperature
2) Increase myelination
3) Increase diameter

Question 26

2 kinds of synpases:

Answer 26

1) Electrical

2) Chemical

Question 27

What are chemical synapses?

Answer 27

1) An action potential reaches the axon terminal
2) Voltage-Gated Ca2+ Channels open and calcium comes in
3) Causes the synaptic vescicles, containing neurotransmitters, to fuse with the presynaptic terminal
4) Neurotransmitters travel across the synaptic cleft
5) To the Ligand-Gated Sodium Channels of the postsynaptic cell, causing them to open
6) Sodium will come in due to the concentration gradient and act as another stimulus

Question 28

2 kinds of Postsynaptic Potentials:

Answer 28

1) Excitatory

2) Inhibitory

Question 29

What is an excitatory postsynaptic potential?

Answer 29

A positive movement in the membrane potential, bringing it closer to threshold. Easier to get an action potential.

Question 30

What is an inhibitory postsynaptic potential?

Answer 30

A negative movement in the membrane potential; this could happen by opening up a negative ion, Cl-, channel. Harder to get an action potential.