Nodes of Ranvier Myelinated (white matter) vs Unmyelinated (grey matter) Classification of Neurons 1. Functional (sensory neurons, motor neurons, interneurons) 2. Structural (multipolar, bipolar, unipolar) 9.5 Cell Membrane Potential Resting Potential / Threshold Potential / Action Potential 1. Neuron membrane maintains resting potential 2. Threshold stimulus is received 3. Sodium channels open 4. Sodium ions diffuse inward, depolarizing the membrane 5. Potassium channels open 6. Potassium ions diffuse outward, repolarizing the membrane 7. The resulting action potential causes a local bioelectric current that stimulates adjacent portions of the membrane. 8. Wave of action potentials travel the length of the axon as a nerve impulse 9.6 Nerve Impulse
Name:_________________________ *Propagation of action potentials along a nerve axon Impulse Conduction – speed of an impulse proportionate to diameter of axon (greater diameter = faster impulse) Myelinated axons conduct faster than unmyelinated axons Example: Motor neuron associated with skeletal muscle 120 m/2 Sensory neuron on skin (unmyelinated) travels at .5 m/s A: Neuron (Presynaptic) B: Neuron (Postsynaptic) 1. Mitochondria 2. Synaptic vesicle full of neurotransmitter 3. Autoreceptor 4. Synaptic cleft 5. Neurotransmitter receptor 6. Calcium Channel 7. Fused vesicle releasing neurotransmitter 8. Neurotransmitter re-uptake pump 9.7 The Synapse Synapse – junction between two communicating neurons Nerve pathway – nerve impulse travels from neuron to neuron Synaptic Transmission Dendrite cell body along axon synapse (gap) To complete the signal, a NEUROTRANSMITTER is released at the gap to signal the next neuron Excitatory – increase membrane permeability, increases chance for threshold to be achieved Inhibitory – decrease membrane permeability, decrease chance for threshold to be achieved Types of Neurotransmitters Acetylcholine – stimulates muscle contraction
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- Fall '16