Cellular Potentials and Charge

Elements have varying charge potentials due to orbiting charged components.
Negative charge in a cell isn't an absence of charge, but a different type of charge (like a car battery).
Everything has potential for electrical charge, and its interaction with other elements determines conductivity.
Electricity is referred to as potential, representing how much charge exists.

The plasma membrane separates charge, creating potential (inside negative, outside positive) due to active transport mechanisms.
The cell membrane acts as a barrier, maintaining a separation of charge where intracellular is negative and extracellular is positive.
Even the fluid, fatty acid-containing membrane has charge potential.
Transmembrane potential refers to the total separation of charge across the cell membrane.

Charge is polarized across the membrane; opposite charges are maintained on either side (like North/South poles).
Cells aim to return to a homeostatic state with this charge distribution.
Charge is measured in volts (or millivolts in the body); devices measuring heart activity detect voltage.
A resting, unstimulated neuron has a charge of -70 to -85 millivolts.
Potential electrical difference is the separation of positive and negative charges across the membrane.
A cell works to equilibrate charge; the greater the difference in charge across the membrane, the harder it must work.
A resting cell has a negative intracellular charge and a positive extracellular charge and is considered polarized and undisturbed.

Action potential occurs when a cell responds to its environment, causing a rapid, short-lived reversal of intracellular charge.
During action potential, the cell becomes depolarized (charges are no longer opposite inside and outside).
Repolarization is the process of returning the cell to its resting, polarized state (negative inside, positive outside).
Depolarization: resting membrane potential changes from negative to positive.
Repolarization: making the potential inside the cell negative again.

Threshold is the amount of change in intracellular charge required to trigger an action potential.
Sodium (Na+) is constantly trying to enter the cell.
Pumps work to remove sodium to maintain resting potential unless a stimulus is received.
The cell tolerates small fluctuations in intracellular negativity caused by "sneaky" sodium entry, counteracted by pumps.
A significant influx of sodium, like a "concert crowd," is needed to reach the threshold and trigger action potential.

Non-gated channels allow some sodium entry, while gated channels regulate sodium flow with a protein barrier.
Gated channels open in response to stimuli, allowing a massive rush of sodium into the cell.
- The non gated channels allows only a little bit of sodium to come in.
- The gated channels are bigger, allowing more sodium to come into the cell.

Threshold ensures that only purposeful stimuli, not just constant sodium leakage, trigger action potential.
Enough change in intracellular charge from sodium influx is needed to signal the need for action.
Key terms: membrane potential, potential difference, resting potential, action potential, and threshold.
A threshold change in intracellular charge must be met before action, because cells are "constantly getting sneaky tokens."