NERVE IMPULSES The neuron membrane Three major types
NERVE IMPULSES
The neuron membrane Three major types of embedded proteins • Sodium (Na+) gated channels • Potassium (K+) gated channels • Sodium-Potassium Pump Gated channels opened/closed based on conditions, allow facilitated diffusion when open Pumps – use ATP to do active transport (move against the concentration gradient
https: //www. youtube. com/watch? v=90 cj 4 NX 87 Yk IV. Nerve Impulses A. Resting potential – at rest, the neuron cell membrane is polarized (more positive outside than inside) to -70 m. V
B. Depolarization – a stimulus depolarizes the membrane allowing Na+ into the cell. 1. If the impulse is strong enough (reaches the threshold) an Action Potential is generated (goes down the length of the axon) All or none
C. Repolarization – K+ ions rush out of the cell in response to the Na+ coming in D. Hyperpolarization – prevents another action potential from starting before one is finished (refractor period) https: //www. youtube. com /watch? v=SHBn. Exxub 8
4. Return to resting potential Sodium and potassium channels close, Na+/K+ Pump restores resting potential
Saltatory conduction – transmission of an impulse through myelination
Communication at the Synapse Direction of impulse
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• Action potential reaches axon terminals of presynaptic cell • Causes Ca 2+ to enter the cell • Signals for the release of neurotransmitter into the synapse by exocytosis • Neurotransmitter diffuses across synapse, binds to receptors on post-synaptic cell • Opens sodium gates to start an action potential in the post synaptic cell
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