What happens when K+ or Na+ spontaneously flows out or into the cell and what type of gradient does it create
the Na+/K+ will re-establish the concentration gradient creating an electrochemical gradient (gradient in charge and [solute]
What is the firing of a signal down an axon called
ACTION POTENTIAL
What is DEPOLARIZATION
the loss of the difference in charge between the inside and outside of the plasma membrane due to a migration of Na ions to the interior
What is REPOLARIZATION
change in the membrane potential that returns it to a more negative value after the depolarization of an action potential which changed the membrane potential to positive value
what is HYPERPOLARIZATION
change in a cell’s membrane potential that makes it more negative (opposite of a depolarization) —> insist its action potentials by increasing the stimulus required (action potential threshold)
What does hyper polarization prevent from accidentally happening
prevents misfiring from happening until it needs to
What is the RESTING POTENTIAL and what is its value
at rest, there are relatively more Na ions outside the neuron and more K ions inside that neuron
value: 70 mV
How do action potentials occur
Na+ voltage gated channels:
* activation gate closed
* both gates open
* inactivation gate closed (triggered at threshold - not capable of opening)
How do neurons recover from an action potential
Voltage gated channels along with “leaky” channels exist in addition to the Na+/K+ pump and they also help to restore the concentration gradients
When there’s an influx of Na+ what happens
The influx of Na+ causes the membrane potential to reach THRESHOLD POTENTAIL which induces the firing of an ACTION POTENTIAL
At the peak of the action potential what happens
The K+ efflux begins to counteract the Na+ influx
What happens after the efflux of K+ ions
the membrane potential decreases past resting potential (hyper polarization) to prevent a premature firing
Does the membrane potential keep decreasing or does it stop
When the membrane potential reaches a specific area in the axon, it returns to resting potential via the Na+/K+ pump and leaky channels
What is CONTIGUOUS CONDUCTION / How does it work
the action potential spreads down the axon this means:
* current flow between the active area (peak of action potential) and the adjacent inactive area
* this reduced the potential in the inactive area and the original active area returns to resting potential
* new active area induces an action potential in the next area
What is the REFRACTORY PERIOD
prevents backward current flow because an area cannot be restimulated by normal events
What are the 2 types of refractory periods
ABSOLUTE & RELATIVE
what is an ABSOLUTE REFRACTORY PERIOD
the membrane portion that had just undergone an action potential cannot be restimultated (Na+ inactivation gates are closed)
what is a RELATIVE REFRACTORY PERIOD
the area can be restimulated but only by a stimulus that is stronger than normal (K+ gates have not yet closed)
