Physiology 6/7 Graded Potentials And Action Potentials

Front 1

what does opening ligand gated channels produce?

Back 1

this produces graded potentials

Front 2

what does opening of voltage gated channels produce?

Back 2

this produces action potentials

Front 3

what are some of the changes that can lead to the production of an electrical signal?

Back 3

a change in electrical field

chemical messenger

stiumulus (sound, vibration)

spontaneous change in potential from imbalances in the leak-pump cycle

Front 4

what kind of potentials does stimulating mechanosensitive channels produce?

Back 4

this produces graded potentials

Front 5

what generates the resting membrane potential?

Back 5

this is generated by background channels. These spontaneously open in the absence of external stimuli

Front 6

what are the main characteristics of graded potentials?

Back 6

these are Small, Local changes

May be hyperpolarizing or Depolarizing

vary in amplitude and duration

magnitude of potential is related to the magnitude of the stimulus

bi directional flow

decremental conduction

Front 7

What happens with mixed cation channels are opened? What type of change does this lead to?

Back 7

This is an excitatory synapse.

When this is opened by (ACH), small outward flux of K+, large influx of Na+

Leads to depolarization

Front 8

What happens when K+ or Cl- channels are opened? what type of change does this lead to?

Back 8

this is an inhibitory synapse

K+ outflow, or Cl- Inflow, leads to hyperpolarization

Front 9

What are some excitatory neurotransmitters? 3

Back 9

glutamate, aspartate, ACH

Front 10

what are some inhibitory neurotransmitters? 2

Back 10

glycine, GABA

Front 11

what determines which direction a current flow is moving?

Back 11

this is determined by the direction the positive charges are flowing

Front 12

what are 4 examples of graded potentials?

Back 12

post synaptic portentials

end plate potentials

pacemaker potentials

slow wave potentials

Front 13

what is temporal summation?

Back 13

summation of several ESPS from in SINGLE presynaptic neuron, only adjusts the time interval between firings

Front 14

what is spatial summation?

Back 14

summation of several ESPS from Different Presynaptic inputs

Front 15

what zone of a neuron initiates action potentials?

Back 15

the axon hillock

Front 16

When are all voltage gated channels triggers for action potentials?

Back 16

these are all triggered at threshold, they just have different built in delays, which produces the given effects

Front 17

In sodium channels, what are the two gates, and what are their relative speeds?

Back 17

both are activated during threshold, there is a channel opening which is very rapid (Na+ influx), and the slow closing inactivation gate

Front 18

What is the speed and flow of potassium channels in action potentials?

Back 18

these are also activated at threshold, but are slow opening. When they open, K+ rushes out

Front 19

what type of potential activates an action potential?

Back 19

this is activated by a large graded depolarization reaching the axon hillock (10-15mv)

Front 20

What is the first channel opened during an action potential? What does it cause?

Back 20

at threshold, sodium channels open first, leading to a rush of Na+ into the cell, depolarizing cell (rising phase)

Front 21

after Na+ rushes into a cell during depolarization, what happens?

Back 21

At the peak of the action potential, the Na+ slow moving inactivation gate closes, ending Na+'s rush in.

Front 22

Once Na+ stops going into the cell during an action potential, what happens next?

Back 22

Now K+ channels have opened up, causing K+ to leave the cell (escaping the positive charge) generates the falling phase.

Front 23

After an action potential has fired, what restores the original concentration gradients of Na+ and K+?

Back 23

this is done buy the Na+/K+ pump pushing K+ back into cell, and Na+ out of the cell

Front 24

What does Tetrodotoxin and Topical lidocaine do?

Back 24

these both inhibit voltage gated Na+ channels

Front 25

what is the purpose of the refractory period?

Back 25

this ensures one way propagation of action potentials.

limits frequency of potentials

Front 26

what causes the absolute refractory period?

Back 26

this is caused by most voltage gated Na+ channels being inactivated, NO stimulus can elicit an action potential

Front 27

what causes the relative refractory period?

Back 27

this is causes by residual inactivation of voltage gated Na+ channels.

action potentials CAN occur here, but require a supranormal stimulus

Front 28

What does Primary Hyperkalemic Paralysis do to skeletal muscles?

Back 28

this causes hyperexcitability of skeletal muscles, leading to spontaneous action potentials.

Leads to accomodation by Na+ channels and paralysis due to channel inactivation.

Front 29

why does a hyperkalemic state raise the resting potential closer to threshold?

Back 29

this in essence reduces the drive between ICF and ECF K+'s concentration gradient. So with K+ have less of a say in the resting membrane potential....it will shift MORE towards Na+'s potential (+30, so depolarizing)

Front 30

Why does accommodation cause paralysis?

Back 30

Continuous depolarization allows some the voltage gated Na+ channels to inactivate, so even when the membrane is depolarized, not enough Na+ channels are available to initiate an action potential

Front 31

what does a the time constant mean?

Back 31

this shows how fast a cell can depolarize. a small time constant means fast depolariziation

t=Rm X Cm (time constant= membrane resistance times capacitance)

Front 32

what is the length constant?

Back 32

this is how far a depolarizing current will spread along the membrane. A larger length constant the further the current will spread along the membrane

Determined by the root of membrane resistance over internal resistance

Front 33

what is contiguous conduction?

Back 33

this is the conduction found in unmyelinated fibers, action potentials spread along the whole membrane. Slow

Front 34

what is saltatory conduction?

Back 34

this is rapid conduction in myelinated fibers. Impulse jumps over sections of myelination

Front 35

why is saltatory conduction faster?

Back 35

because the action potential does not have to be regenerated at myelinated sections.
up to 50x faster