Block 3 Flashcards
injection of a negative current into a neuron
hyperpolarization
injection of a positive current into a neuron
depolarization
region of instability in the current/voltage relationship
action potential
basis of neural signaling
abrupt depolarization
What happens during rapid depolarization?
takes the membrane potential past zero, approaches the sodium equilibrium potential but does not quite get there
What happens during rapid hyperpolarization?
takes the membrane potential farther way from zero, approaches the potassium equilibrium potential but does not quite get there
slightly depolarizing stimulus that is necessary to produce an action potential in an axon
threshold
___ mV of charge brings neuron to just above resting potential
10
the overall concentrations of K, Na, Cl on the outside and inside of the axon do not dramatically change, so vM must fluctuate because the ____ of the ion change (movement of ions in vs. movement of ions out)
relative contributions
the ability of ions to move across the membrane
conductance
two ions currents that drive the entire action potential
sodium and potassium
a positive electrical signal causes ___ conductance to increase, so it enters the axon fast
sodium
conductance dependent upon an initial electrical signal
voltage dependent
charge on the inside of an axon
voltage
Voltage and conductance relationship depends upon the opening and closing of channels for what ions?
sodium and potassium
What kind of gate is the first sodium gate inside the membrane? (blocked by amino acids when at rest, unblocked during depolarization, and on a timer so the gate can only stay open for a millisecond)
voltage and time sensitive gate
second sodium gate on cytoplasmic side of membrane blocks channel; this gate produces the refractory period by closing the gate regardless of the state of other gate and timer
inactivation gate
this delays opening the potassium channel for 1 msc, allowing for the Na conductance to depolarize the entire axon
delay mechanism
prevents sodium and potassium channels from being interchangeable
selectivity filter
channels exist at ___, which are gaps in myelin sheathing where the axon is exposed
nodes of Ranvier
the movement of action potential down the axon
propogation
the electrically excitable domain
presynaptic terminal
__ entry into the terminal facilitates the fusion of vesicles to the plasma membrane, and release of neurotransmitters
Calcium
presynaptic communication depends on __ and __
calcium and sodium
__ is responsible for endocytosis and replenishment of the free pool of vesicles
calcium
Where does threshold usually occur?
axon hillock
