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Unit 2 Notes: Nerve Impulses

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1 Unit 2 Notes: Nerve Impulses

2 (1) Nerve Impulses What is it? Nerve Impulse = Electrical Current
Messages sent to and from neurons Used to respond to stimuli Ultimately maintains homeostasis Nerve Impulse = Electrical Current Comes from the flow of positively charged ions Ions move across the neuron’s membrane Also called an “Action Potential”

3 (2) Neuron Membranes & Ions
Sodium & Potassium Pumps: In the membrane of neurons Only open when stimulated by neurotransmitter Ions: Charged particles Sodium = Na+ = Positive Charge Potassium = K+ = Positive Charge Movement of Ion = Movement of Charges = Electrical Current

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5 (3) Neuron Resting Potential
Resting Potential: The natural charge distribution across a neuron’s membrane. Na+ on the Outside K+ on the Inside Inside = More Negative, Outside = More Positive Membrane = Polarized = Imbalance K+ channel a little “loose”: Some K+ leaks OUT of the neuron Build up of MORE positive ions outside of the membrane

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7 (4) Depolarization & Repolarization
Depolarization: (Remove imbalance) Na+ pump opens  Na+ flows inward Depolarization  Temporary Balance REMEMBER: In this scenario, balance is NOT normal in this part of your body! Your body will FORCE repolarization! Repolarization: (Imbalance Again) K+ pump opens  TONS of K+ flows outward Repolarization REMEMBER: K+ needs to be in, and Na+ out!

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9 (5) Action Potential The action potential IS the nerve impulse, which IS Depolarization  Repolarization! Process: 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

10 (6) Regaining Resting Potential
Action Potential caused Na+ to be on the inside, and K+ to be on the outside. Change = NOT NORMAL Not Normal  Homeostasis kicks in! Na+ and K+ Pumps Actively Transport (using ATP) Na+ and K+ back out/in of the axon Na+ pushes out K+ pushes in Resting Potential regained

11 (7) 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

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