1. Unit 2 Notes: Nerve Impulses
Wednesday
Unit 2 Notes: Nerve Impulses

2. (1) Nerve Impulses Nerve Impulse = Electrical Current
Comes from the flow of positively charged ions
Ions move across the neuron’s membrane

3. (2) Neuron Membranes & Ions
Neurons have Na+ and K+ pumps within their membranes.
Na+ gets pumped out of the neuron
K+ gets pumped into the neuron
Na+ and K+ ions can only move across the membrane through these “pumps”.

5. (3) Neuron Resting Potential
K+ channel a little “loose”:
Some K+ leaks OUT of the neuron
Build up of MORE positive ions outside of the membrane
Neuron Inside = More Negative
Neuron Outside = More positive
Neuron membrane = Polarized

7. (4) Ion & Charge Imbalance
K+ ions leak out:
More (+) charges outside than in
Change in Charges
Change = No more Homeostasis = AHHHH!

8. (5) Depolarization & Repolarization
Na+ ions need to flow in
Na+ pump opens  Na+ flows inward
Depolarization  Temporary Balance
Now more (+) on the inside than outside!
Repolarization:
K+ ions need to leave
K+ pump opens  TONS of K+ flows outward
Repolarization

9. http://upload. wikimedia

10. (6) Action Potential
Action Potential = Movement of Na+ and K+ ions in and out (across) the neuron membrane.
Process:
Cycle of depolarization + repolarization
Stimulus  Opening of Na+ Pumps  Movement Inward of Na+  Depolarization & Shutting of Na+ Pumps
Depolarization  Opening of K+ Pumps  Movement Outward of K+  Repolarization & Shutting of K+ Pumps

12. (7) Regaining Resting Potential
Action Potential caused imbalance of Na+ and K+ ions down axon membrane
Change = NOT NORMAL
Na+ and K+ Pumps Actively Transport (using ATP) Na+ and K+ back out/in of the axon
Na+ pushes out
K+ pushes in
More negative inside + Pumps Close

13. (8) Myelin & Action Potential
Myelin = Insulation along axon
Creates “gaps” between Na+ and K+ pumps in membrane…
“Gaps”  electrical jumping
Ions fly down to the next set of pumps
Increases Speed of Current / Impulse