Psychology 1000 September 27, 2016
How do neurons work?
Next time: The Brain
Scan: p. 76-87
How do neurons produce an electrical signal?
How does a neuron code intensity?
How does one neuron communicate with another?
how does a cell produce an electrical signal?
• Neuron is like a bag of fluid with holes in it (It is semipermeable- ions able to float back
• Has ions in it (Cl-, A-, K+, Na+) on inside
• On outside it has ions (Na+, K+, Cl-) but outside there are many many more sodium.
With the different charges, it produces an electrical charge on the cell membrane
• Negative on inside relative to the outside
• Neuron is like a tiny battery that is charged from the ions
• If the neuron gets stimulated= action potential
The action potential ***EXAM***…
- Neuron just sitting there (no stimulated) it is in resting potential (negative electrical
- When it is stimulating- the wholes in the cell membrane get bigger, as it gets bigger,
more ions can come in and out, and therefore the neuron can become more positive-
moving more positive= depolarization Na+ inflow (coming in)
- If the sodium reaches a certain point (-55)- threshold= the wholes open as wide as they
can more sodium floods in and goes to +40
- Repolarization- K+ outflow
- Now the neuron has to recover after +40. We start to repolarize by kicking out the
potassium (pump). Potassium goes out and you drop in charge
- It doesn’t stop at -70, it overdoes it (drops below resting potential), then you let things
float back and it will finally go back to resting potential (-70)
- Takes about 7millaseconds to get back to resting potential
- Hyperpolarization- below -70 (below resting potential)
- Absolute refractory period- the time between the peak of +40 and the bottom of
hyperpolarization. Nothing can stimulate neuron when it is in the absolute
- Relatively refractory period- you can stimulate neuron, but it takes more intense
stimulus because you have to move it from -90 to back up Neural Communication
- The electrical signal moves down the axon by changing the relative concentration in the
- Action potential only happens in the axon (set off at the axon hillock, where the axon
meets the cell body)
- Grade potentials- in the cell body and dendrites, accumulate until they are up at a
➢ Neuron fires on all-or-non fashion (neurons fire or they don’t fire)
➢ Height of “spike” fixed (only stops at +40, doesn’t go up)
How to code intensity?
➢ Neurons have different thresholds
➢ Strong stimulus will hit more neurons
➢ Frequency of firing- how fast the neurons fire
➢ How many neurons are stimulated?
➢ Intensity directly proportional to frequency of firing (at some point, you can’t fire it any
faster- due to the absolute refractory period because nothing will happen there)
How do cells communicate?
there’s a space between the sensory neurons and motor neurons= synapse
- Sherrington’s experiment (inferring the synapse)- looking at a dog by stimulating dogs
paw, how fast would it take the dog to move their paw. He called the gap the synapse
- Gap between the axon and dendrite
- Vesicles- do the synaptic communication. The bags of chemicals need to get across the