lecture 21 Flashcards
define membrane potential
The measurement of the difference in the charge across the membrane; is electrical and very important for neuron communication
leakage channels
– the non-gated channels that are always open
the types of gated channels
o Chemical (ligand) channels – open in response to a chemical signal
o Voltage-gated channels – opens in response to a change in membrane potential or voltage
o Mechanically gated channels – opens form a mechanical stimulus, from pressure, vibration, etc.
electrochemical gradient
This determines the direction that ions will flow through an open ion channel. Is a combination of concentration and electrical field gradients.
resting membrane potential
Resting membrane potential is maintained mostly through the process of the Sodium-Potassium pump
depolarization
is a decrease in membrane potential inside the cell when sodium goes in and the inside of the membrane becomes less negative
repolarization
– when the membrane potential turns back to being more negative because Potassium flows back in.
hyperpolarization
is an increase in membrane potential, and is when the inside of the cell membrane becomes more negative than where it started
graded potential
is a short-range signal that is like local depolarization. Is mostly with the dendrites and cell bodies
The current is decremental, and the stronger the stimulus the more voltage charge.as the signal travels away is gets weaker and weaker. If the cell receives signals from multiple sources that can all add up together
a change in membrane potential that varies in size and that decreases in amplitude as it moves away from the stimulus point
action potential
is a long distance signal that can travel across the entire cell. Is mostly dealing with the axon.
define threshold
o This is the max a action potential or growth can be. If depolarization reaches threshold, then an action potential is initiated.
No matter how much stronger it gets, after reaching threshold, it will give the same action potential each time
- Discuss the sequence of events that initiate and propagate an action potential
o An action potential is initiated when a stimulus depolarizes the neuron membrane to reach the threshold potential, causing voltage-gated sodium channels to open, leading to a rapid influx of sodium ions which further depolarizes the membrane; this depolarization then spreads along the axon, triggering the opening of sodium channels in the adjacent region, propagating the action potential down the axon until it reaches the axon terminal, where neurotransmitters are released; the process then concludes with the closing of sodium channels and the opening of potassium channels, allowing potassium ions to flow out and repolarize the membrane, returning it to its resting potential.
absolute refractory periods
– the time right when the action potential happens, and immediately after during repolarization. No matter what stimulus it receives, it cannot initiate another neuron to fire again, because the sodium-channels have not reset.
The cell is unable to respond to additional stimuli
relative refractory period
is the time after an action potential where the neuron can gradually become excitable again. Occurs during repolarization and hyperpolarization (if it occurs)
electrical synapse
These are very rare, and is a gap junction where electrical signals can travel directly through the gap junction to the next cell
Benefit: allows for a very quick response
Disadvantage: does not allow for any complex communication
* Is in the heart and muscles of the eyes