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From the Backyard Brains laboratory comes a new experiment:
The effect temperature on neurons.
Here i have my standard cocroach leg prep, an additional thermometer showing the
temperature in Fahrenheits.
Notice, at room temperature the cockroach leg responds rather nicely to manipulation by the Q-tip.
Brrrr! Cold, outdoor Michigan.
10 degrees and windy.
Let's go to our experiment in the garage,
where it's twenty degrees, and no wind.
Now I'm bringing the cockroach leg preparation from inside the house now
into the garage,
and as the temperature drops to around twenty degrees, the neurons in the
cockroach leg will become inactive
and will lose their ability to fire action potentials.
This is due to the ion channels themselves being affected by the temperature as the
temperature drops below threshold, the ion channels can no longer open, and action
potentials can no longer occur.
Let's watch the oscilloscope iPhone I have.
as I manipulate the leg with the Q-tip,
as the temperature drops to around twenty degrees, you'll notice the amplitude
of the activity is decreasing and decreasing...until...
it is now almost completely gone.
But are they gone permanently?
Now I'm returning the very cold cockroach leg back into the house to warm-up
and though it almost instantaneously warms back up
to room temperature,
there's no neuronal activity present.
Why is this?
Perhaps the leg is dead.
But we're patient scientists, and we will wait.
I will manipulate the leg with my Q-tip and observe the neural activity on my iPhone.
I'll speed this up in the interest of time for the video.
Wow! It appears the neural activity has returned! Why was there a lag? You should
discuss this with your students.
You can see two minutes later,
the spontaneous activity has returned,
and we have a quite healty response
to manipulaton
Now, you can play this cool-down,
warm-up cycle games over and over again.
Here's a sped-up video of me bringing the cockroach leg back into the garage.
And again, around twenty degrees it disappears.
Now, what if I heat the cockroach leg above room temperature?
Is there a temperature at which the neurons will stop firing?
I have lit a candle and placed it to the side, but I'll first check to see
if I get a nice evoked discharge at room temperature.
And indeed I do.
Now, I'l move the flame directly underneath the cockroach leg to
slowly heat it and see the effect of rising temperature on neural activity.
Wow! I immediately see an increase in firing rate!
And at 120 degrees the neurons discharge all their ions, and????
and at 160 degrees, the tissue gives its last breath of electricity.
I don't think the activity will come back.
Let's test it!
Back to room temperature...and no response.
You can use this temperature control experiment in both the cold and warming
directions to explain ion channel kinetics to your students.
We look forward to hearing you ideas!