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Unit 2 Notes: Nerve Impulses

Unit 2 Notes: Nerve Impulses. Wednesday 2-24-2010. (1) Nerve Impulses. Nerve Impulse = Electrical Current Comes from the flow of positively charged ions Ions move across the neuron’s membrane. (2) Neuron Membranes & Ions. Neurons have Na+ and K+ pumps within their membranes.

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Unit 2 Notes: Nerve Impulses

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  1. Unit 2 Notes:Nerve Impulses Wednesday 2-24-2010

  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”.

  4. (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

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

  6. (5) Depolarization & Repolarization • Depolarization: • 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

  7. http://upload.wikimedia.org/wikipedia/commons/2/2f/Action_potential_propagation_animation.gifhttp://upload.wikimedia.org/wikipedia/commons/2/2f/Action_potential_propagation_animation.gif

  8. (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

  9. http://www.youtube.com/watch?v=90cj4NX87Yk&NR=1

  10. (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

  11. (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

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