Nerve Impulses

Introduction: Now we will delve deeper into how a neuron works. In this section you will get the scientific explanation, a simple example, as well as an interesting explanation I was taught in high school that involves the men's bathroom.

*A quick definition:

~Nerve impulses: communicates information within the nervous system

Resting Potential:

~Resting Potential: Axon is not conducting an impulse

--> Unique to animal nerve and muscle tissue

--> Diffusion of charged ions along the cell membrane

--> Neurons and muscles cells are the only ones that do this

The How of Resting Potential

Above is a picture from http://www.millerandlevine. come. It represents the resting potential, moving to the action potential.

~The How of Resting Potential

1. At rest, body is using 1/3 of its energy in maintaining resting potential

2. Sodium-Potassium Pump: moves charged ions out of the cell so the

Inside of the cell is at -70mV comparative to the outside of the cell

3. Happens ridiculously fast (in 1000’s of a second)

4. Holding the neuron at resting state so they are ready to “fire!”

The How of Action Potential

The picture below, from http://www.unm.edu, shows how action potential works close up with the numerical figures of the millivolts.

~The How of the Action Potential

1. A stimulus opens the Sodium-Potassium Pump gates

2. Sodium gates open first, so positively charged ions flow into the axon

Changing the membrane potential from -70 to +40mV

3. Membrane potential change is called depolarization, charge changes

From negative to a positive

4. Potassium gates open second, so potassium flows out and the action

Potential changes from +40 to -70mV.

5. The resting potential resumes and this is called repolarization

*All of this happens within 3/1000 of a second...so REALLY, REALLY FAST!!!

(http://www.inkycircus.com)

The Toilet Example

Now for the exciting part! Here is the example I was given in high school. Our teacher took us into the men's bathroom, stood on the toilet, and commenced his example. I have never forgotten in and I understood it so much better after that.

~The Toilet Example

1. Toilet waiting to be flushed, it is at its resting potential.

2. Threshold: all or none. You either press the handle all the way to flush,

Or only part of the way and it remains.

3. Flush the toilet, “gates open” new water (positively charged ions)

comes in as the soiled water (sodium ions) goes out.

4. New water settles (everyone knows some of the old water is still there so a little bit of potassium stays, but there is more sodium than potassium again) as rest of old water (potassium ions) flows out and
then returns to resting state.

The Synapse

Below is a picture of a synapse from http://universe-review.ca.

When action potential gets to the end of the axon, the neurotransmitter is secreted to stimulate connecting neurons or muscle cells

Transmissions across a synapse is carried out by neurotransmitters. Once secreted, it receives a response from the receiving neuron either toward inhibition or excitation. Excitation results in sodium diffusing to the receiving neuron. Inhibition is a result of potassium being diffused.

A Simple Example

~A Simple Example

1. Get a pin prick on your finger

2. Sensory neurons bring the change in environment (pain, in this case)

From the skin

3. Neurons of the spinal cord process this information and decide what to

Do

4. The motor neurons take this decision, carries output, to muscles saying,

“You should move your hand away from that.”

5. Effectors, muscle, take that advice and move.

Here is a good example of a stretch reflex I found at

http://trc.ucdavis.edu/biosci10v/bis10v/media/ch25/stretch_reflex_v2.html

Conclusion: I truly hope the toilet example made sense. I was so confused when my teacher first explained the whole process, but after going through the toilet one, it was crystal clear. You have just experienced what happens within 3/1000 of a second. It happened a ridiculous amount of times while you read this and even more as I typed it! Next up, a deeper look at the CNS.