Brain electric field sense of some types of fish. Each sensory system begins with specialized receptor cells, such as light-receptive neurons in the retina of the eye, or vibration-sensitive neurons in the cochlea of the ear. The axons of sensory receptor cells travel into the spinal cord or brain, where they transmit their signals to a first-order sensory nucleus dedicated to one specific sensory modality. This primary sensory nucleus sends information to higher-order sensory areas that are dedicated to the same modality. Eventually, via a way-station in the thalamus, the signals are sent to the cerebral cortex, where they are processed
Electrically powered spacecraft propulsion Electrically powered spacecraft propulsion An electrically-powered spacecraft propulsion system uses electrical energy to change the velocity of a spacecraft. Most of these kinds of spacecraft propulsion systems work by electrically expelling propellant (reaction mass) at high speed, but electrodynamic tethers work by interacting with a planet's magnetic field. Electric thrusters typically use much less propellant than chemical rockets because they have a higher exhaust speed (operate at a higher specific impulse) than chemical rockets. Due to limited electric power the thrust is much weaker compared to chemical rockets, but electric propulsion can provide a small thrust for a long time.