2 Functional Properties of Neurons 1 Irritability Ability
2 Functional Properties of Neurons 1. Irritability § Ability to respond to stimuli 2. Conductivity § Ability to transmit an impulse Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
How neurons communicate Action Potential § electrical signal that travels on the membrane of a neuron § based on movements of ions between the outside and inside of the cell Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
§ If the stimulus reaches threshold then an action potential is started in the neuron and will travel down the membrane (This is called a nerve impulse) This is the ALL or NONE PRINCIPLE. Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Steps to a Nerve Impulse § Polarized: Resting neuron § Inside membrane is slightly – § Outside membrane is slightly + § Most membrane channels are closed, there is some normal diffusion of K+ or Na+ between cell and the environment through the sodium/potassium pump (active transport) After Stimulus Occurs § Depolarization § Sodium (Na+) channels open allowing Na+ to diffuse into the cell quickly § This causes the inside to become + (outside -) § Repolarize: K+ gates open in order to allow K+ to diffuse out of the cell – this restores the membrane (+ outside, - inside) Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Nerve Impulses Figure 7. 9 a–b Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Nerve Impulses Figure 7. 9 c–d Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Nerve Impulses § Refractory Period § K+ must be moved back to the inside of the cell and NA+ must be pumped out of the cell in order to prepare for the next impulse § The sodium-potassium pump ( a membrane channel), using ATP, restores the original configuration Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Nerve Impulses Figure 7. 9 e–f Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Simple Video showing Action Potential § http: //video. google. com/videoplay? docid=6890770586678681705&ei=3 qb 9 Sq. Px. O 5_ar. QKQpin. BA&hl=en# § http: //outreach. mcb. harvard. edu/animations/actio npotential. swf § http: //video. google. com/videoplay? docid=6890770586678681705&ei=3 qb 9 Sq. Px. O 5_ar. QKQpin. BA&hl=en#docid=-4821246047499143591 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Transmission of a Signal at Synapses § Impulses are able to cross the synapse to another nerve § Neurotransmitter is released from a presynaptic nerve’s axon terminal http: //highered. mcgrawhill. com/olcweb/cgi/pluginpop. cgi? it=swf: : 535: : /sites/dl/free/0072437316/120068/bio 02. s wf: : Endocytosis%20 and%20 Exocytosis § The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter § An action potential is started in the postsynaptic dendrite Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
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