Electrophysiology Flashcards
Ion channels: _________ proteins that span the membrane and, when open, permit the passage of certain ions
integral
Ion channels are _______; they permit the passage of some ions, but not others.
selective
the higher the probability that a channel is open, the higher the _____________, or permeability.
conductance
ligand-gated channels open and close in response to a specific ____________ (ligand) including neurotransmitters, hormones and particular ions
chemical stimulus
the _______ receptor for acetylcholine (ACh) at the motor end plate is an ion channel that opens when ACh binds to it.
nicotinic
these are ion channels that are always open
Leakage channels
the membrane’s permeability for potassium is much ________ than it is for sodium
higher
mechanically gated channels opens and closes in response to ___________ in the form of vibration (sound waves), pressure (touch) or tissue stretching.
mechanical stimulation
voltage gated channels opens in response to a change in ______________ (voltage)
membrane potential
it is a process wherein the cell interior becomes less negative due to influx of cations
depolarization
its is a process wherein the cell interior becomes more negative due to influx of anions
hyperpolarization
it refers to the number of channels that are open in a membrane; it increases when channels are opening, and it decreases when channels are closing
conductance
it is a force determined by the concentration difference across the membrane
concentration force
a force determined by the electrical difference across the membrane (membrane potential)
electrical force
At EQUILIBRIUM, these two forces are always equal
but opposite in direction
concentration and electrical
[Action potential]
the voltage-gated sodium channel is closed and not capable of opening (___________) when the membrane’s from peak to resting potential (+30 mV to -70 mV)
inactivated
[Action potential]
the voltage-gated sodium channel is open (________) when the membrane potential is from threshold to peak potential (-50 mV to +30 mV)
activated
[Action potential]
the voltage-gated sodium channel is ________ but capable of opening when the membrane potential is at resting potential (-70 mV)
closed
It is the potential difference generated across a membrane because of a concentration difference of an ion. It is generated only if the membrane is permeable to the ion
Diffusion potential
At _________________, the chemical and electrical driving forces that act on an ion are equal and opposite, and no further net diffusion of the ion occurs
electrochemical equilibrium
It is used to calculate the ion’s equilibrium potential at a given concentration gradient
Nernst equation
Nernst equation for ions with single charge (e.g. Na +)
Vm = 61.5 x LOG ([ion]out / [ion] in)
Nernst equation for ions with double charge (e.g. Ca 2+)
Vm = 30.75 x LOG ([ion]out / [ion] in)
Approximate value for Na + equilibrium potential (in nerve & skeletal muscle)?
+65 mV
Approximate value for Ca 2+ equilibrium potential (in nerve & skeletal muscle)?
+120 mV
Approximate value for K+ equilibrium potential (in nerve & skeletal muscle)?
-85 mV
Approximate value for Cl- equilibrium potential (in nerve & skeletal muscle)?
-85 mV
The flux of ungated K+ channels must be an __________ from the cell
EFFLUX
___________ happens when there’s too much potassium in the blood, reducing the efflux of K+ and further depolarizing the cell
Hyperkalemia
_________ can accelerate the efflux of K+, hyperpolarizing the cell
Hypokalemia
A CELL’S RESTING MEMBRANE POTENTIAL IS VERY
__________ TO CHANGES IN THE EXTRACELLULAR
POTASSIUM CONCENTRATION
SENSITIVE
A CELL’S RESTING MEMBRANE POTENTIAL IS ______________ TO CHANGES IN THE EXTRACELLULAR SODIUM CONCENTRATION
NOT SENSITIVE
property of excitable cells (i.e., nerve, muscle) that consists of a rapid depolarization, or upstroke, followed by repolarization of the membrane potential. It is propagating and an “all-or-none” process.
Action potential
______ membrane potential is the result of the high resting conductance to K+, which drives the membrane potential toward the K+ equilibrium potential.
Resting
The __________ is the brief portion at the peak of the action potential when the membrane potential is positive
overshoot
__________ block these voltage-sensitive Na+ channels
and abolish action potentials
Tetrodotoxin (TTX)
_________ blocks voltage-gated K+ channels.
Tetraethylammonium (TEA)
the period during which another action potential cannot be elicited, no matter how large the stimulus.
Absolute Refractory Period
period that begins at the end of the absolute refractory period and continues until the membrane potential returns to the resting level.
Relative Refractory Period
occurs when the cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential.
Accomodation
_________ of action potentials occurs by the spread of local currents to adjacent areas of membrane, which are then depolarized to threshold and generate action potentials
Propagation
__________ acts as an insulator around nerve axons
and increases conduction velocity. Myelinated nerves exhibit saltatory conduction because action potentials can be generated only at the _________
Myelin, nodes of Ranvier
What happens during the upstroke of the nerve action
potential?
(A) there is net outward current and the cell interior becomes more negative
(B) there is net outward current and the cell interior becomes less negative
(C) there is net inward current and the cell interior becomes more negative
(D) there is net inward current and the cell interior becomes less negative
D
The neurotoxin purified from the liver of a puffer fish affects which process?
A. Inhibits calcium channel
B. Opens sodium channel
C. Opens calcium channel
D. Blocks sodium channel
D
A channel lined with negatively charged groups will be
selective for these ions
A. Sodium ions
B. Calcium ions
C. Chloride ions
D. Phosphate ions
Both A & B
