generating an action potential Flashcards
the fluid on either side of the cell membrane differ in charge because?
of their basic ionic compositions
A natural affinity exists between anions and ______
cation
anions are defined as?
negatively charged ions
cations are defined as?
poisitvely charged ions
Charges that are positives and positive will _____ each other
repel because like electrical charges repel each other
charges that are positive and negatively charged will ______ each other.
attract
Sodium is a _______ ion
positive
Chloride ions are negative or positive?
negative
sodium and chloride will ______ each other?
attract each other because the sodium is positively charged and the chloride is negatively charged.
potassium is negative or positively charged?
positively charged
Sodium and potassium will ______ each other.
repel each other because they are both positively charged, and like charged ions repel one another
What two ions have a high concentration outside the cell?
sodium and chloride
What two things are highly concentrated inside the cell?
potassium and other negatively charged protein molecules
Define resting membrane potential?
The difference in electrical charge between the intracellular state and the extracellular state of an unstimulated neuron.
the extracellular state of a neuron is _______ charged.
positively
the intracellular state of a neuron is ______ charged.
negatively
the difference between the intracellular and extracellular sides of a neuron is approximately _____ millivolts.
70
the interior fluid is of the cell is approximately _____ _____ millivolts relative to the fluid outside of the cell.
minus 70
the cell membrane that has a resting membrane potential of 70 millivolts, at rest is ______ and holds the potential to _____
polarized
change
the most extremem change from the cell’s resting potential is called?
the action potential
describe action potential?
a quick combination of chemical and electrical activity inside and outside of the cell that actually reverses the polarity of the axon cell membrane, the intracellular fluid becomes more positive charge relative to the extracellular fluid after an action potential has occured.
how long does an action potential last?
1 millisecond
because ions carry an electrical charge. The term _____ _____ describe the difference in electrical charge between barriers.
voltage gradient
what two process operate to maintain the resting potential to set the stage for the action potential?
electrostatic pressure
diffusion
define electrostatic pressure
the force exerted by the attraction or repulsion of electrical charges
describe how diffusion is prevented in the resting potential
the cellular barrier prevents the cations and anions to evenly distribute between intracellular and extracellular.
ion channels in the phospholipid bilayer of the cellular membrane are closed to _____ when the neuron is at resting potential?
sodium
the neuron has a threshold potential which means what?
any stimulation below the threshold potential results in little or no change in the membrane potential.
what are graded potentials?
ultralocalized voltage changes that increase or decrease membrane voltage
hyperpolarizations results from what?
when the extracellular fluid becomes more positive because of either an efflux of potassium or an influx of cloride ions.
hyperpolarization ______ the membrane voltage, make the membrane more _____ charged.
increases
negatively
depolarization in an action potential results form what?
an influx of sodium ions, decreasing the membrane voltage and making the membrane more positively charged.
What is the source that fuels the sodium/potassium pump
the pump uses most of the ATP that the neuron produces
Describe the function of the Na/K pump affecting the cell membrane
This pump comes into play when the K+ pumps continue to dump too much potassium out of the cell causing Hyperpolarisation (-90, the cell is more negative). This pump activates to regain a resting potential for the cell, inforcing the cell to have only 2 K+ intracellularly and 3Na+ extracellularly.
describe a subthreshold stimulus?
a stimulus that results in some ion channels opening and raising the membrane potential some but not to the threshold and results in no effect is observed.
If a stimulus exceeds the threshold for excitation, what happens?
the sodium channels open up and the neuron fires with everything the membrane has reaching +30 mV
A neuron must return to its ______ in order to carry out another action potential
resting potential
At what rate do neurons fire at?
500 HTZ or 500 times per second
How long does each action potential take to occur
2 milliseconds including the refractory period
after an action potential takes place, potassium channels are _____ which leads to a neuron approaching what type of state
OPEN
resting membrane potential
During repolarization, what pressure are operating on potassium movement
electrostatic and diffusion pressures
Once potassium chanels reach a resting state of ___, what mechanism of action occurs next
-70
Potassium channels slowly close allowing slow leakage of potassium to continue, this leads to hyperpolarization
During hyperpolarization, what type of charge takes place
an even greater negative charge relative to the extracellular space
(K is + and is continuing to move outside of the cell)
as potassium continue to shift out of the neuron, it accumilates around the _____
Cell membrane
In hyperpolarization, potassium accumilated around the cell membrane making it have a ____ charge, until the potassium diffuses away from what mechanism?
Positive
this happens by diffusion and electrostatic pressure along with potassium harvesting
once the membrane potential reaches ________, a second set of voltage gated channels open, releasing potassium out of the neuron.
this is known as?
+30
potassium efflux
when do potassium voltage gated channels open?
when membrane potential reaches +30
when does sodium channels close?
membrane potential reaches +30
describe what takes place during absolute refractory period
From threshold to threshold (-55 to -70) causing a total inability for the neuron to respond to any charge/impulse
potassium efflux is accelerated by what two forces?
electrostatic pressure and diffusion
as potassium efflux occurs during _______, the membrane potential becomes more negative.
Repolarization
membrane potential is first reached following depolarization in about ____ millisecond, however, further potassium will leak out called ________
1
hyperpolarization
what occurs during relative refractory period
occurs after repolarisation threshold is met (-70) and takes place until resting potential is reached. During this time, the neuron may respond to more insistent depolarizing signals
What uses the majority fo the ATP the neuron produces?
the Na-Potassium Pump
