Circuitry And Action Potentials

Front 1

Passive stimulus vs. active stimulus

Back 1

Passive=follow the stimulus (subthreshold)
active=exceed in amplitude or duration of the initial stimulus (action potential)

Front 2

Potassium concentration inside the axon

Back 2

140mM

Front 3

Potassium concentration outside the axon

Back 3

5mM

Front 4

Sodium concentration outside the axons

Back 4

145mM

Front 5

Sodium concentration inside the axon

Back 5

5-15mM

Front 6

Chloride Concentration inside the axon

Back 6

4-30mM

Front 7

Chloride Concentration outside the axon

Back 7

110mM

Front 8

What maintains the resting potential of a neuron? how is the resting potential maintained?

Back 8

Ion Gradients and Ion Channels generate the resting potential.

The differences in the concentrations of specific ions in/outside of cell
AND
The differences in permeability of the membrane to those ions

maintained via active transport through ion channel to create the ion gradients

Front 9

At rest, Neuronal membranes have a high permeability to ____ while no permeability to __,___, and ___

Back 9

K+=high permeability
Na+, Ca2+, and Cl-=no permeability

remember this is at REST

Front 10

What are leak channels?

Back 10

leak channels are open potassium channels.

Front 11

How does the high intracelluar [K+] react in this instance? what does it create?

what kind of equilibrium occurs? how does it occur?

Back 11

high intracellular [K+]=>net flux of K+ to outside of cell.

This flux of K+ (removal of (+) charges) from inside to outside creates (-) intracelluar resting potential=>equilibrium

this equilibrium occurs because flow of K+ from in to out is balanced by the electric repulsion of the K+ ions on the extracellular side=electrostatic equilibrium

basically, the K+ don't want to go outside as much because they are going against their proton gradient. opposing membrane potential (+) vs. (+)

Front 12

concentration gradient is maintained by...?

what happens if there is no ATP?

Back 12

active transporters that transport K+ back into the cell

need ATP. if no ATP, gradient is lost and memb potential=0mV

Front 13

Reveral/Maximum potentials for ions. What do they mean?

Back 13

EK+= -84mV
ENa+= +84mV
ECa2+= +125mV
ECl-= -60mV

mean that if a specific gate for that ion opened up, the ion would flow until a value of ? mV was reached.

ex) If chloride channel opened, chloride would flow until membrane potential would stabilize at -60mV.

Front 14

What ion has the greatest effect on the resting membrane potental?

what does this mean?

what cells maintain this resting potential?

Back 14

K+ because it has the highest permeability. means that small changes in extracellular [K+] can have dramatic effects on neuronal excitability.

glial cells help maintain the extracellular levels of K+ by actively taking it up

Front 15

what is the duration of an AP and where on the wave is it measured?

Back 15

duration is the time btw the beginning of the change in Vm and return to baseline. usually measured as the width at half the height of the wave

Front 16

How can you ID different neurons by their action potential. give 3 examples.

Back 16

can ID neuronal type by it's duration (width) some neurons are much faster than other.

ex.) purkinje (cerebellum)=high frequency, FAST, 180us
-CA1 pyramidal (hippocampus)=810us "Medium"
-Dopamine (midbrain/movement)=4ms SLOW

Front 17

What proof is there that axons are voltage gated/selectively permeable and not temp breakdown w/ fully permeability?

Back 17

If the membrane temporarily broke down, the memb potential would go to 0. Instead, the membrane potential rises to +40. Suggests nerve membrances have mechanism to make the transiently permeable to Na+

Front 18

What is the refractory period?

absolute?

relative?

Back 18

period where a 2nd AP can't be generated

absolute=overall duration of AP. additional AP CANNOT be induced no matter how intense stimulus is

relative=when neuron is after-hyperpolarized/less excitable. needs more intense stimulation to generate new AP

Front 19

overshoot?

Back 19

amount that membrane potential exceeds 0mV. Usually 20+ to 50+ depending on the neuron

Front 20

amplitude/spike height

Back 20

maximum difference btw peak and after hyperpolarization

Front 21

distance where the decay reaches the 1/e (37%) of it's original value=?

measures what?

Back 21

the length constant.

measures of how far an electrical signal will PASSIVELY travel away from its source.

Front 22

axons with lower membrane resistances are ______ and therefore have ________, transmitting signals a _____distance.


axons with high membrane resistances are _____ and therefore have ______, transmitting signals a ____distance.

Back 22

leakier and therefore have shorter length constants, transmitting signal short distances.

less leaky and therefore have a higher length constant, transmitting signals a longer distance/larger charge in membrane potential.

Front 23

how do you make the length constant as large as possible?

Back 23

high membrane resistance (less leaky), resistance of axoplasm and extracellular fluid should be low

Front 24

the plasma membrane acts as a capacitor which is responsible for...

Back 24

the lag at the end of the pulse as the membr. potential falls beack into resting state. stores charge at the beginning and end of the pulse.

Front 25

what is Tau/what does is imply?

Back 25

time constant=time it takes for response to rise or fall 63%. determines how fast a membrane can change it's membrane potential

dependent on membrane resistance and capacitance

Front 26

Unmyelinated axon "wave". how does it work?

Back 26

passive spread of current triggers voltage sensors on Na-V channels, and this inward current thru the NA-V Channels boosts the passively carried current=wave of depolarization opening new Na channels further down axon.

Front 27

after wave beings moving down the axon, what happens next?

Back 27

Na channels close behind AP (refractory) and K channel open to restore the membrane potential. this, and the opening of the Na channels repeated down length of axon

Front 28

speed of AP is dependent upon what?

Back 28

the density of the Na and K voltage gated channels, how big the axon is

Front 29

you can also see/measure AP in the ______

Back 29

dendrites. much smaller/wider (reduced and slower)=back propagation.

Front 30

nodes of ranvier is less?

causes signals to propagate....

Back 30

leaky.

faster

Front 31

saltatory conduction is what?

Back 31

voltage-gated channels concentrated in the gaps (nodes of ranvier)=AP jumps from node to node=saltatory conduction

Front 32

multiple sclerosis results in loss of function of neurons because

Back 32

loss/degeneration of myelin=>interference with normal axonal conduction/screws up saltatory conduction