Electricity

The presence and motion of matter that has a property of electric charge.

Electromagnetism.

Magnetic field.

The movement of electric charge that produces a magnetic field.

Produced by the presence of an electric charge.

Protons are positive, electrons are negative, and neutrons are neutral.

Coulomb (C).

The net charge of an isolated system remains constant during any physical process.

Attractive if opposite signs and repulsive if the same sign.

The strength of the force between two charged particles based on their charges and distance.

An invisible zone of influence around a charge.

The total electric field at one point is the sum of all individual fields created by multiple charges.

They point away from positive charges and toward negative charges; more lines indicate a stronger field.

Stronger field.

They attract each other.

They repel each other.

They connect points with the same electrical potential (voltage).

Electric field lines are always perpendicular to equipotential lines.

The energy per charge required to move from one point to another.

Materials that have electrons in the outer shell that move easily, such as metals like copper, silver, or gold.

Materials where electrons are tightly bound and do not move freely, such as glass, rubber, or plastic.

Materials that are not conductive in pure form but can increase conductivity with a dopant, such as silicon or germanium.

V = I x R; if voltage increases, current increases as long as resistance stays the same.

A passive component that resists the flow of current, providing some resistance.

What goes into a junction equals what comes out; no current is lost at a wire split.

The total voltage around any loop equals zero, based on conservation of energy.

P = U x I, where P is power, U is voltage, and I is current.

How fast electrical energy is used or supplied; the rate of doing work or transferring energy.

Slows down current, doesn't store energy for later, and converts energy to heat.

A capacitor consists of two metal plates separated by a dielectric, storing charge and energy in an electric field between the plates.

A resistor, a capacitor, and sometimes a battery (voltage source).

The capacitor starts empty, current flows when the circuit is closed, and the capacitor charges until fully charged, at which point the current stops.

The charged capacitor acts like a battery, pushing current through the resistor and losing charge over time until fully discharged.

The time constant τ = R X C indicates how fast the charging or discharging occurs; after 5 time constants, the capacitor is fully charged or discharged.

Using an electric current to activate cells.

Cells that generate and respond to electrical signals, including nerve cells, muscle cells, and secretory cells.

Controls what enters and exits the cell, maintains electrical potential, detects signals, conducts pulses, and supports enzyme activity and metabolism.

Resting potential is the stable electrical charge of a cell, typically around -70 mV, maintained by Na+/K+ pumps.

The equilibrium potential for a single ion, showing the voltage needed to balance the concentration gradient of that ion.

It includes multiple ions and their permeabilities, providing a more comprehensive view of resting potential.

Activation gate is closed; Inactivation gate is open; no Na+ flow.

The activation gate opens, Na+ rushes in, making the inside more positive.

The inactivation gate closes, stopping Na+ inflow.

The activation gate closes and the inactivation gate opens again, preparing the channel for the next impulse.

K+ channels open more slowly than Na+ channels and do not have an inactivation gate; they open and close gradually.

It describes how the cell membrane acts like an electrical circuit and how membrane potential changes during an action potential.

An excitatory postsynaptic potential caused by excitatory transmitters, making the membrane more positive and bringing the neuron closer to firing an action potential.

Temporal summation involves repeated signals over time, while spatial summation involves signals from multiple synapses at once.

An inhibitory postsynaptic potential caused by inhibitory transmitters, making the membrane more negative and making firing less likely.

The all-or-nothing principle; the threshold must be reached to trigger an action potential.

One alpha motor neuron and all its innervated muscle fibers.

It describes how strong and long a stimulus must be to trigger a response, comparing nerve or muscle excitability.

The minimum current needed if applied for a very long time.

The minimum time required to activate a neuron with twice the rheobase.

A process where the inside of the cell becomes less negative, making it more likely to fire.

A process where the inside of the cell becomes more negative, making it harder to fire.

Larger myelinated fibers are easier to stimulate due to shorter chronaxy and lower resistance, producing a stronger activation at each node of Ranvier.

Muscle fibers are recruited starting with small fibers, then intermediate, and finally large fast-twitch fibers to conserve energy and extend endurance.

Electrical stimulation activates large fibers before small ones, reversing the natural order of recruitment.

Improves blood flow, reduces pressure sore risk, and helps maintain bone density and heart health.

ENS (Electrical Nerve Stimulation), EMS (Electrical Muscle Stimulation), MNS (Magnetic Nerve Stimulation), TMS (Transcranial Magnetic Stimulation).

Muscle fibers undergo spontaneous fibrillations, lose the ability to sustain contractions, lose structure, and can be replaced by fat and collagen over time.

It is used for conditions like facial nerve paralysis to restore facial movements.

A device that connects the nervous system to help or replace functions, which can be cognitive, sensory, or motor.

To send pulses that block pain signals in neuropathic pain treatments.

Stimulates the motor cortex to help with pain management, either epidurally or through TMS.

To target deep brain areas such as the ACC and PAG.

They deliver medication directly into the spinal fluid.

It connects an electrode to stimulate tissue, allowing electrical devices to communicate with biological systems by converting electron flow into ion flow.

The movement of ions across their membranes.

-50 to -90 mV.

Direct muscle activation from stimulating efferent (motor) nerve fibers.

Stimulation of afferent (sensory) fibers that triggers a reflex through the spinal cord.

Atrial depolarization.

Ventricular depolarization.

It represents ventricular contraction and recovery.

Brain electrical activity via scalp electrodes.

0 to +/- 1 mV.

Mostly under 50 Hz.

Epilepsy diagnosis, sleep studies, and brain-computer interfaces.

Brain responds but not time-locked, such as during thoughts or imagination.

Early, time-locked reactions to a stimulus, like sound or flash.

Later, time-locked responses that reflect cognitive processing like attention and memory.