Unit 2 Notes: Nerve Impulses

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Unit 2 Notes: Nerve Impulses

Presentation transcript:

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

(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. 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”.

(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

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

(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

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

(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

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

(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

(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