Nerve Physiology Flashcards
When N gates open, K+ moves _____
out of the cell
All or None Law
-once an action potential is created, the nerve signal can’t be stopped
Ca++ causes Ach to_____
move down terminal bouton to release Ach from synaptic vesicles to synaptic cleft via exocytosis
Ca++ is usually higher _____
extracellularly
If pt has low K+ levels
the resting membrane potential is more negative and farther from action potential threshold, so it will take a stronger stimulus to elicit an action potential
Acetylcholinesterase
enzyme that breaks down Ach into an acetate ion and choline
If pt has high K+ levels
resting membrane potential would be closer to threshold for an action potential so a weaker stimulus would cause depolarization
Depolarization
- inside cell becomes less negative
- voltage dependent gaits (m & h) begin to open and close
Optimal Sarcomere Length
-2.0-2.2 microns
Nerve Impulse
cascade of ionic exchanges along the nerve until it reaches terminal end
Na+–K+ pump
pump in plasma membrane that pumps out 3 Na+ per every 2 K+ ions it brings in, creating a net efflux of positive charges
(20% of membrane potential)
n gates
- face intracellularly
- most closed at -100mv
- most open at -0mv
- open and close slowly
Depolarization is due to:
movement of Na+ into cell through open Na+ gates (m & h gates)
m Gates
- face extracellarly
- most closed at -100mv
- most open at -0mv
- open/close rapidly
Na+ channel inactive state
-m gate open and h gate closed
OR
-m gate closed and h gate closed
When the cell is at rest, it is ______
polarized
negative inside and positive outside
Local Potential
- (graded/generator potential)
- create small changes in membrane potential that can be summed
At rest, ____ ions line up along inside of cell and ___ ions on outside
- negative
- positive
K+ moves ____ cell during repolarization
-out of the cell
Repolarization
-making the inside of cell more negative again by taking K+ out of cell
h gates
- face intracellularly
- most open at -100mv
- most closed at -0mv
- open/close slowly
Postsynaptic receptors are
nicotinic (Ach binds here)
Choline
- byproduct of Ach breakdown
- taken back up by presynaptic membrane to make new Ach
Why is the inside of the cell negative?
- Na-K pump: net leaving of positive
- membrane more permeable to K+
- large negatively charged intracellular proteins (can’t diffuse)
Membrane Potential
-difference in electrical changes between 2 sides of a cell membrane
Hyperpolarization
Inside of cell becomes more negative
Potential
potential energy in the charge separation
What happens around -60mv?
-enough h gates are closing slowly and m gates opening rapidly to result in an influx of enough Na+ to reach threshold to create an action potential
2 Types of Local Potentials
- depolarization
- hyperpolarization
Resting Potential of:
- Small neurons
- Large Neurons/Skeletal Mm
- Smooth Muscle
- Small: -70mv
- Large/Skel: -90mv
- Smooth Mm: -50mv
m gates begin to open when voltage gets:
less negative
At rest m gates are ____
closed
At rest h gates are ____
Open
h gate begins to close when voltage gets ___
less negative
When m & h gates are open, Na+ moves ____
into cell
n gates open when ____
inside becomes less negative
Repolarization is due to:
movement of K+ out of cell through n gates
Na+ channel resting state=
m gate closed & h gate open
Na+ channel Active state
-m gate open, h gate open
Sodium goes ____ cell during depolarization
into
It is easier for K+ to pass through the membrane than Na+ because:
there are usually more K+ channels open than Na+
A-
Large negative molecules inside cells that are too big to diffuse and contribute to the negative charge of the inside of the cell
what accounts for 80% of the membrane potential?
- K+ concentration gradient
- so, resting potential is due to the differences in K+ levels
