Flashcards in Neural Electrophysiology Deck (53)
What are the 2 types of electrical signals from the neuron?
- propagated action potential that can travel long distances
- local grated potential that do not spread from their site of formation
Define propagated action potential.
can travel long distances
Define local grated potential.
do not spread from their site of formation
What is the potential difference?
- separation of charge ( negative from positive)
- measured in volts
In living things charges come from what?
ions separated by membranes; they can move through channels in membranes
Potential difference in living things is measured in____.
What are the 2 types of ion channels?
- Passive (aka leakage) channels that ions move freely through
- Active (aka gated) channels that require energy
What are some characteristics of leakage channels?
- open randomly
- cells generally contain more K channels than Na channels
What are some characteristics of gated channels?
- can be open or closed (we can control them)
- there are 3 types
a. voltage-gated channels
b. ligand-gated channel
c. mechanically-gated channel
What are voltage gated channels?
- a gated channel that opens or closes due to voltage change
What are ligand-gated channels?
- gated channels that open or close based on chemical stimuli
What are mechanically-gated channels?
- gated channels that open by mechanical stimulation
What is resting membrane potential?
- potential differnce measured acroos the cell membrane of an unstimulated (resting) nerve cell
- normally -60 to -70 mV
What is resting membrane potential?
- result of different composition of ICF (k and protiens) compared to ECF (Na and Cl)
What is determined by the relative permeability of membrane to Na and P?
What are graded potentials?
small local deviations from resting membrane potential
What are 2 types of graded potential?
hyperpolarized (when membrane potential becomes more negative)
depolarized ( when membrane potential becomes more positive
When something is hyper polarized is is more ______.
When something is depolarized it is more_______.
What is an action potential?
(aka nerve impulse)
- brief, transient, local period of membrane depolarization
- membrane potential changes from -70mV to +30 mV and back again
What are the phases of an action potential?
Depolarization is when....
resting membrane potential become more positive
Repolarization is when....
return of depolarization membrane potential to ward resting membrane potential
After- Hyperpolerization is when ....
there is a movement of resting membrane potential away from 0
- eg. -70 > -85 mV
- extra potassium leaks out of the cell causing the voltage to drop to -85mV
What is the threshold potential?
- the point at which a local potential becomes a self-propagating action potential
What is the all or nothing phenomenon?
- if the threshold potential is exceeded, an action potential is generated
- if the threshold potential is NOT exceeded, NO action potential is generated
- all action potentials are identical
What is the refractory period?
time following the onset of an action potential when it is impossible or difficult to produce a second one
(NO action potential during the ABSOLUTE REFRACTORY period; at the top of the curve on the graph)
What are some charactersitics of sodium gates?
- voltage-gated channels have 2 gates (activation gate, and inactivation gate (when closed it will not respond to stimuli)
- In a resting neuron the inactivation gate i open and the activation gate is closed
- depolarizaton opens activation gates, then closes in activation gates
When the cell is resting the inside is more ____ and the outside is more_____.
- inside is more negative
- outside is more positive