BIOFOUND 5.6 Nerve Signaling pt 1

Electrical signaling in nerve and muscle cells

Involves changes in membrane potential caused by the movement of ions across the cell membrane.

Five ion gradients

Sodium (Na⁺), Potassium (K⁺), Calcium (Ca²⁺), Chloride (Cl⁻), and large negatively charged proteins; small ions can diffuse when channels are open, while proteins cannot.

Ion diffusion and membrane permeability

Ions move down their concentration gradients when the membrane is permeable; Na⁺ and Ca²⁺ enter the cell, K⁺ leaves the cell, Cl⁻ usually enters the cell.

Effect of ion diffusion on membrane charge

Sodium and calcium make the membrane more positive; potassium makes it more negative; chloride usually makes it more negative too.

Polarized / Polarization

A condition where the inside of the cell membrane is negatively charged relative to the outside.

Membrane potential

The electrical charge difference across the membrane, measured in millivolts (mV).

Resting membrane potential

The stable membrane voltage of a resting cell, usually around -70 mV, meaning the inside is 70 mV more negative than the outside.

Sodium and potassium leak channels

Allow passive movement of Na⁺ into the cell and K⁺ out of the cell, helping set and maintain resting membrane potential.

Resting potential and leak channels

The constant leak of K⁺ (more than Na⁺) out of the cell makes the inside more negative; different leak channel densities cause different resting potentials in different cells.

Gated ion channels

Proteins that open or close in response to stimuli, allowing specific ions to move and change the membrane potential.

Trace (in membrane potential studies)

A graph that records voltage over time; the flat part represents resting potential, upward movement indicates depolarization, and downward movement indicates repolarization or hyperpolarization.

Types of gated ion channels

Ligand-gated (respond to chemicals), mechanically gated (respond to physical force), voltage-gated (respond to changes in membrane potential).

Special function of voltage-gated channels

They can generate action potentials—large, rapid electrical signals used in communication by neurons and muscle cells.