Neurobio Exam 2: Learn & Delete Set

Front 1

Nernst Equation in Words

Back 1

Equilibrium Potential (Volts) =

[ Diffusion / ( Ion Charge x F ) ] ln ( out / in )

Front 2

Ohm's Law

Back 2

Voltage = Current X Resistance

Front 3

Capacitance

Back 3

The amount that can be stored in a capacitor.

Front 4

Capacitance =

Back 4

Charge / Voltage

Front 5

Series capacitors make capacitance...

Back 5

go down.

Front 6

Parallel capacitors make capacitance...

Back 6

go up.

Front 7

Higher Veq is caused by...

Back 7

more force (higher resistance).

Front 8

1/G(ion)

Back 8

What is G?

How we talk about resistance of membrane to ions.

Front 9

Goldman Equation Simplified

Back 9

Vm = Equilibrium Potential / Conductance

We can measure these to determine membrane potential.

Front 10

Lower the membrane resistance and...

Back 10

more current leaks out, so it decays faster resulting in a shorter length constant.

Front 11

First Action Potential Experiment

Back 11

Took Sodium out of water surrounding (neuron?). Saw the action potential decreased. Concluded Sodium must be critical to the AP.

Read more about this in book.

Front 12

What does a voltage clamp let you measure?

Back 12

How much current you inject to maintain voltage helps you figure out resistance with Ohm's Law.

Front 13

Results of the Voltage Clamp Experiment

(2)

Back 13

1. Shows there is 2 parts to the action potential.

2. Sodium and Potassium are involved.

Front 14

Some Qualities of APs (4)

Back 14

1. They are all or none

2. They are always the same in the same neurons

3. You can do lots of them in a row (regenerative)

4. The are unidirectional (unless initiated non-physiologically in the middle of the axon and then they shoot both ways).

Front 15

What do passes 1-4 do?

Back 15

This is where the voltage sensor is. When the inside gets positive, it pushes pass 4 up which pulls at 5 and 6 causes them to twist open.

Front 16

What do the intracellular loops do in ion channels?

Back 16

They cause inactivity.

Front 17

Quantal Yield

Back 17

Different synapses release different numbers of vesicles.

Example: neuromuscular junction synapses have huge quantal yields.

Different kinds of neurons can also have different vesicle sizes. Vesicle size often depends on the neurotransmitter type.

Front 18

RIM Proteins

Back 18

Scaffolding that brings calcium channels towards snares.

Front 19

What kind of molecule is Botox?

Back 19

Protease

Front 20

Calcium & the Time Window

Back 20

Adding calcium to cause an endplate potential only works in a very narrow time window. If there is no calcium in the area and you add calcium it only makes the synapse functional if you add the Calcium at the exact right moment where depolarization is happening in the terminal.

Front 21

Vesicle Fusion Observations

Back 21

Timing is important (for voltage gated calcium channel opening and vesicle fusion and end plate potential triggering; both occur in less than 2 ms).

Therefore vesicles need to be docked near or on target membrane and primed to fuse with membrane quickly (all slow ATP dependent processes have to have already happened).

Front 22

Specifics of the Patch Clamp Workings

Back 22

Patch pipette seals onto surface of ion channel and forms a high resistance seal.

It measures voltage.

It injects current into feedback circuit so that the pipette voltage matches the command voltage. The amount of current needed to keep the two voltages equal is what is recorded.

This allows you to see ion flow.

Front 23

Patch Clamp Student Video Take Homes

Back 23

1. Patchclamp recording began in the late 1970’sand is also reffered to as cell-attached patch. This technique uses a patchpipette (electrode) into a plasma membrane of a cell and the high resistancecreated is measured in ohms. This prevents ion flow between a pipette andmembrane.

2. The clamp corresponds to the extracellularpotential of a small patch underneath isolation. For example, TTX was found inbacteria of pufferfish and showed how voltage gated Sodium channels areblocked. The importance of a patch pipette is the voltage and current injectedthrough feedback and the response during a depolarization step.

3. The experiments show how not all channels openimmediately after membrane potential occurs and the driving force getsinfluenced by the different ionic components in the cell.

Front 24

Metabotropic Receptors

Back 24

GPCR, G-proteins, secondary messengers.

No direct change in membrane potential.

Slow.

Front 25

Two ways to use Voltage Clamp

Back 25

1. Set command voltage to elicit currents

2. Use presynaptic stimulation to observe currents

Front 26

Structure of Ligand-Gated Ion Channels

Back 26

5 subunits. Each subunit has many transmembrane amines. Ligand binding site. Some gates that can swing open to let ions in.

Front 27

How did we figure out the structure of Ligand-Gated Ion Channels?

Back 27

Blow darts with Curare. Paralyzed animals.

This toxin blocked acetylcholine receptors.

Examining this in frog eggs let them examine different potential candidates for this channel: over express candidates in the egg. Add acetylcholine to cause inward current. Add curare and inward current in inhibited. This let them find the channels.

Front 28

Difference Between Current and Potential

Back 28

Current on top and Potential on bottom.

Front 29

Passive Parts of Neurons

Back 29

Myelin sheath, membrane resistance, length and time constants

Front 30

Factors for Strength (4)

Back 30

# of postsynaptic receptors: more = stronger

Ca+ concentration

Receptor Affinity

# of Presynaptic Vesicles Released

Front 31

How is excess NT taken up?

Back 31

Via plasma membrane symporters (with Na) on presynaptic or glial plasma membranes.

Front 32

Synaptic Vesicle Recycling Article Takeaway

Back 32

Synaptic vesicle retrieval is critical to continuous synaptic transmission.

In flies there was a high temp mutation that caused paralysis because vesicles could not be recycled because of a dynemin mutation.

Front 33

Scaffolding Proteins in the Presynaptic Density

Back 33

Actin binds to CamK2 which binds to PSD-95 which holds neuroligands and key receptors in place.

Neuroligands and neurexin bind to each other.

Cadherins bind to each other.

Front 34

How did researchers discover functions of PSD-95 and other receptors?

Back 34

Antibody affinity purification: isolate protein antigens of interest, but into column with suspected antibodies, and if you get a match not much will come out of column.

Front 35

When do action potentials arise?

Back 35

After supra-threshold depolarization, which opens voltage gated sodium channels.

Front 36

What sets the time of integration as well as the attenuation of more distal synaptic inputs?

Back 36

Cable properties.

Front 37

What increases the size and speed of the PSP and where is it located?

Back 37

Active properties in the dendrites.

Front 38

What does backpropagation do?

Back 38

It can allow for stronger integration for specifically timed inputs.