Chapter 4 Flashcards
resting potential
membrane potential of cells at rest (RMP)
- -70 mV
membrane potential
separation of positive and negative charges across a membrane
polarization
when the membrane potential is other than 0 mV
depolarization
membrane potential moves closer to 0 mV from RMP
repolarization
membrane returns to resting potential after depolarization
hyperpolarization
membrane becomes more polarized than at resting potential
electrical signals are produced by changes in _____
ion movement
positive charges flow in –> _______
depolarization
positive charges flow out –> _________
repolarization
ion movement results from changes in ________ of cell membrane to ions
permeability
leak channels
open all the time - unregulated diffusion
gated channels
can open and close
voltage gated channels
respond to changes in mp
chemical gated channels
respond to chemical messengers
mechanical gated channels
respond to stretch
graded potentials
serve as short-distance signals
- occurs in small, specialized region of excitable cell membranes
- magnitude of GP varies directly with the magnitude of the triggering event
- decremental spread - signal gradually decreases
- if big enough, GP can initiate AP
Action potentials
serve as long-distance signals
- brief, rapid, large changes in membrane potential during which inside becomes more (+) than outside
- non-decremental conduction - signal arrives at full speed
- threshold potential mp to which membrane must be depolarized to initiate action potential
GP example
ripple effect
if threshold potential is not met, an AP will _____ occur. Threshold is the _________ point
not
all or none
in neuron, threshold potential is ______ mV
-50 to -55
AP in detail:
Triggering event = _____ from resting potential to _____ potential then rapid depolarization then rapid _______ with a brief _______ and return to resting potential
depolarization
threshold
repolarizatoin
hyperpolarization
Na+ channels
2 gates
- activation - hinge door
- inactivation - ball and chain
K+ channels
1 gate:
either open or closed (hinge)
ion movement during AP
- Na+ gates open = depol (Na+ is rushing in) - open at -55 mV
- Na+ gates close (close by +30mV)
- K+ gates open = repol (K+ is rushing out - open at +30mV)
- resting potential is restored
- Na+/K+ pump restores ion concentration gradient
sodium is pumped ____ and potassium is pumped ____
out
in
refractory period
ensures one way propagation of AP ( a new AP cannot be generated)
Absolute Refractory Period
unresponsive to further stimulate
- Na+ gate are not in resting conformation - ball and chain plugged the opening
Relative Refractory Period
AP only if triggering event is STRONGER than usual
- makes sure AP only occur in one direction
- period of K+ outflux and hyperpolarization (-80mV)
membrane potential
separation of + and - charges across a membrane
resting potential
membrane potential of cells at rest (RMP)
-70 mV
depolarization
membrane potential moves closer to 0 mV from RMP
repolarization
membrane returns to resting potential after depolarization
hyperpolarization
membrane becomes more polarized than at resting potential
is hyperpolarization an upward or downward from RMP
downward
now if diffusion is going to take place, which way will these ions move?
K+ wants to go out, Na+ wants to move in
voltage gated
respond to changes in membrane potential
chemically gated
respond to chemical messengers
