Action Potentials

Flashcards based on lecture notes covering the resting neuron, action potential steps, ion channels, polarization, refractory periods, sodium-potassium pump, myelination, and frequency coding.

Resting Neuron

Described as a 'salty banana' because it has more sodium outside and more potassium inside the cell.

Resting State Ions (Outside Cell)

Sodium (Na+), calcium (Ca2+), and chloride (Cl-) are concentrated outside the cell.

Resting State Ions (Inside Cell)

Potassium (K+) and anions (A-) are concentrated inside the cell.

Action Potential

A specific, rapid change in the membrane potential of a neuron.

EPSPs (Excitatory Postsynaptic Potentials)

PSPs that make the cell more positively charged (less negative), leading to depolarization.

IPSPs (Inhibitory Postsynaptic Potentials)

PSPs that make the cell more negatively charged, leading to hyperpolarization.

Polarized (Cell)

The state of a neuron at rest, characterized by a negative membrane potential (e.g., -65mV).

Hyperpolarized (Cell)

When the cell's membrane potential becomes even more negative than its resting potential.

Depolarized (Cell)

When the cell's membrane potential becomes more positive (less negative) than its resting potential.

Threshold Value

The specific membrane potential (approximately -50 mV) that, if reached by depolarization, triggers an action potential.

Voltage-Gated Sodium Ion Channels

Channels that open rapidly when depolarization reaches the threshold, allowing Na+ ions to rush into the cell, initiating the rising phase of an action potential.

Axon Hillock

Also known as the spike initiation zone, this is the region where action potentials typically begin, possessing a high density of voltage-gated sodium channels.

Spatial Summation

The summing of incoming postsynaptic potentials (PSPs) from different dendrites on a neuron.

Temporal Summation

The summing of incoming postsynaptic potentials (PSPs) from the same dendrite repeatedly over a short period.

Voltage-Gated Potassium Ion Channels

Channels that open slowly after depolarization, allowing K+ ions to leave the cell and contributing to the repolarization phase of an action potential.

Absolute Refractory Period

A period during which sodium channels are inactivated (plugged), making it impossible for the cell to fire another action potential, which prevents backward propagation.

Relative Refractory Period

A period during the 'undershoot' (hyperpolarization) phase when the cell is extra negative, making it harder, but not impossible, to generate another action potential.

Sodium-Potassium Pump

An active transport mechanism that restores the resting potential by pumping 3 Na+ ions out of the cell for every 2 K+ ions pumped into the cell, consuming ATP.

Myelin

An insulating sheath around axons that increases the speed of action potential propagation and reduces the energy required to restore ion balance.

Nodes of Ranvier

Gaps in the myelin sheath along an axon where ion channels are concentrated, allowing the action potential to be regenerated.

Saltatory Conduction

The process by which an action potential 'jumps' from one Node of Ranvier to the next in myelinated axons, increasing speed of propagation.

Frequency Coding

The method by which neurons convey information by changing the rate or frequency of their action potentials (spikes), as opposed to changing their amplitude.