lecture 2 Flashcards
_______________ are the most numerous open channels in the plasma membranes of resting neurons; therefore, resting neurons are more permeable to _______________
Pottasium channels
to K+ than any other ion.
The ________________ keeps K+ concentration high inside the cell, but K+ can ___________________
sodium–potassium pump
diffuse out the open channels.
The membrane potential at which the tendency of K+ ions to diffuse out of the cell down its concentration gradient (chemical force) is equal to________________________) is called the potassium equilibrium potential.
their tendency to diffuse into the cell (electrical force-opposite charges attract
The membrane potential at which the tendency of K+ ions to diffuse out of the cell down its concentration gradient (chemical force) is equal to their tendency to diffuse into the cell (electrical force-opposite charges attract) is called the ___________________________________________
potassium equilibrium potential.
A critical item to remember is Ohm’s Law:
V=IR or I=GV
____________ first described a momentary loss of resting Vm due to the rapid opening of non-specific channels to explain the spiking phenomenon in nerve cells. According to his theory, the membrane became totally permeable allowing all the ions to equilibrate, causing the membrane potential to peak at 0 mV.
Bernstein(1917)
_______________ later performed experiments in which they were able to stimulate and record from the SGA and found surprising results, contrary to what Bernstein had originally postulated.
Hodgkin, Huxley, and Katz
Hodgkin, Huxley and Katz Set-up:
They stimulated the SGA by pressing the switch, sending a positive current into the axon
The resulting depolarization was recorded by the oscilloscope
Response to S1 (using V1 as the voltage source) & S2 (using V2 as the voltage source) (both subthreshold stimuli) →
graded potentials: local, decremental, non-propagating.
Response to S3 (using V3 as the voltage source) (suprathreshold stimulus) → action potential (AP, spike, impulse): regenerative, “all-or-none,” propagating, non-decremental. If the stimulus amplitude is large enough,
it causes Vm to exceed a certain threshold (θ), causing the spike (AP) which peaked at a positive potential, not at zero.
Hodgkin and Katz later performed further experiments and found that Δ[Na+]0 resulted
in changes in the amplitude of the action potential
___________travel down the axon, but only over relatively
short distances and their amplitudes decay exponentially according to the equation:\
Vx= V0e-x/λ; where λ = (rm/ri)1/2
-Graded potentials
What is the length and space constant in this equation
Vx= V0e-x/λ;
and where λ is the distance along the axon over which Vx = V0(1/e) and is known as the length or space constant
Passive Decay of Graded Potentials Formula
Vx = V0e-x/λ
The membrane resistance rm is _____________ to the surface area As of one segment of the axon
inversely proportional
