Electricity Makes It Happen

When your brain is stimulated, brain cells send millions of fast-moving electrical signals along the pathways of your central nervous system. These paths are nerves that branch out into all your muscles. Whenever you move a muscle, it is powered by electricity running through your nervous system!

Move your fingers. Blink your eyes. It happens so fast that it seems automatic. People with healthy bodies hardly have to think about moving a muscle at all. But this is not true for people who are completely paralyzed.

A spinal cord injury, a stroke, or other serious condition can lock people in their bodies. Their brains still produce electrical signals when stimulated. They are alert, intelligent, have memory, and can learn, but since their nervous systems are badly damaged, electrical signals cannot reach their muscles. They can’t move their arms or legs or even speak. People with this “locked-in syndrome” have great difficulty communicating with others.

Dr. Philip Kennedy is a neurologist, a doctor specializing in the nervous system. His remarkable work helps people with locked-in syndrome. Dr. Kennedy invented the “neurotrophic electrode,” a tiny electrical conductor that is implanted above the ear in a patient’s skull.

One of the first people to have Dr. Kennedy’s electrode implanted in his brain was Johnny Ray. Before Johnny was paralyzed by a stroke in 1997, he was a construction worker and musician. His stroke locked him up in a body he can’t move at all.

Now, when Johnny thinks, the implanted electrode carries his brain’s electrical impulses to a computer instead of into his nervous system. While his brain signals can no longer move his fingers to write, or his mouth and tongue to speak, they can control a computer’s cursor the way they once controlled his muscles. He can even create music again, not by playing an instrument with his mouth or hands, but by thinking into his instrument, the computer!

Connecting the electrical impulses of the human brain to the electronic signals of the computer unlocks paralyzed people from their bodies and gives them a tool to more easily communicate with their families and friends­and the world.

Activity: Keep Your Ion the Ball
Did you ever wonder why your sweat and tears taste salty? It’s because the water that makes up nearly 70 percent of your body has salts dissolved in it. These salts­which include compounds of sodium, potassium, magnesium, and calcium­are necessary for good health. A loss of electrolytes, called an electrolyte imbalance, can slow down the transmission of nerve impulses, impair muscle function, and cause an irregular heartbeat. 

Your body loses electrolytes when you sweat. Normally you get all the electrolytes you need from the food you eat. (Bananas and potatoes, for example, contain a lot of potassium.) Because they sweat a great deal, professional and endurance athletes can lose a large quantity of electrolytes during practice and competition. They will often turn to sports drinks to quickly restore the balance. That’s because sports drinks contain a lot of sodium and potassium.

In this experiment you will test the conductivity (ability to conduct electricity) of a variety of beverages to see which ones contain a higher concentration of electrolytes. The beverage that has the highest concentration of electrolytes will have the greatest conductivity.  For more information on conductors and insulators, see “Who Can Resist?”


Activity: Nervous Energy

Nerve impulses travel from one neuron (nerve cell) to another in the form of electrical signals. Each neuron consists of a cell body, short threadlike projections called dendrites, and one longer thread called an axon. The electrical signals are received by the dendrites of a neuron and then passed along the axon to the dendrites of adjacent neurons.
Interestingly, axons and dendrites don’t actually touch. There is a space between them, called a synapse. So how does the electrical signal “jump” the gap? You could say the energy changes form. The electrical current causes chemicals in the axon tip to be released. These chemicals, called neurotransmitters, flow across the synapse and lock on to the dendrite of the next neuron, where they cause new electrical signals to be generated and passed on in the same manner.

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