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Activity: Nervous Energy |
Background
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.
You can use common electronic components to model how nerve impulses
get relayed from one neuron to another in the body.
Materials
- 4 AA batteries
- 2 battery holders [RadioShack Cat. No. 270-408]
- 3-volt DC buzzer [RadioShack Cat. No. 273-053A]
- 1 infrared phototransistor [RadioShack Cat. No. 276-145A]
- 1 jumbo super-bright LED (light-emitting diode) [RadioShack
Cat. No. 276-086A]
- electrical tape
Steps
-
Set up the equipment as shown. Make sure the shorter lead
of the LED is connected to the black wire of the battery holder.
Similarly, make sure the shorter lead of the phototransistor
is connected to the red wire of the other battery holder. Wrap
a small piece of electrical tape around each connection.
-
You should have two circuits. The circuit on the left contains
batteries, wire, and an LED. The circuit on the right contains
batteries, wire, a phototransistor, and a buzzer. Electricity
travels in a loop called a circuit. Every circuit has an energy
source, wires, a load, and a switch.
- Line up the LED with the phototransistor, leaving about a half-inch
of space between them. Then touch the end of the loose red wire
to the long lead of the LED. The LED should light up and the buzzer
should sound. If the buzzer doesn't sound, check the alignment
of the LED and the phototransistor and then repeat until it does.
Questions
Congratulations. You've just modeled how nerve impulses get transmitted
from one neuron to the next. Now test your understanding by answering
the following questions.
-
Which part of the setup represents:
neuron cell bodies? __________________________________
an axon? ___________________________________________
the axon tip? ________________________________________
the synapse? ________________________________________
a dendrite? _________________________________________
the nerve impulse? ___________________________________
- How is the light from the LED like the neurotransmitters released
by an axon tip?
- Why do you think the buzzer was used in this demonstration?
- What might the buzzer represent in the body?
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