Neuro2 - Neuroscience Dr D.G Neuron Physiology Neurons Similar to other somatic cells very distinctive and abundant in their variety of size shape

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Neuroscience 9/17/07 Dr. D.G. Neuron Physiology Neurons: Similar to other somatic cells, very distinctive and abundant in their variety of  size, shape and function. This is unlike other body cells such as liver or heart cells. Semi-permeable= MOST IMPORTANT ELEMENT IN REGARDS TO FIRING  NEURON *IMPORTANT* ion distribution across cell membrane: inside of cell has greater concentration of potassium outside of cell has greater concentration of sodium resting membrane potential (means cell is not firing)= minus 70 millivolts (mV) means that charge inside cell compared to outside of cell is minus 70 mV. -70mV  because it is ready to go, even though called “resting” 2 basic principles: concentration gradients- high concentration to low concentration for equilibrium,  almost always.  electrostatic pressure- opposites attract. Negative ion in negative environment is  repelled to a positive environment.
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At -70mV sodium channel is closed Channels will open when charge raises (-69 mV or greater) In an X,Y graph,  Y is always a function of X When Na enters, action potential is very high, but when Na enters, K leaves and  action potentials decreases quickly Rising phase of action potential is due to the influx of Na Falling phase is due to the deflux of K Classification of neurons Neurons can be classified in two ways:  Structurally: -unipolar -bipolar -multipolar # of processes coming out of that cell body -OR- Functionally: -sensory -motor -interneuron (very important)
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soma=cell body, machinery dendrite-input axon-output myelin-insulator buttons-transfer between cells 9/19/07 sodium potassium ratio in Na K pump is 3:2  3 Na’s go out and 2 K’s come in *when action potential comes below resting (-70mV) it is called a refraction  period and the neuron cannot fire. Relative or absolute refactory periods. All or none principle-either firing or not Glial cells and myelin: In addition to neurons we have billions of glia in the brain as well. Glia are cells  that support neurons. They are involved in many functions: blood-brain barrier is one of  them. Not many things can get across the blood-brain barrier Oligodendrocyte can mylenate more than one axon. CNS
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Schwann cells- glial cells that compose the myelin sheaths of PNS axons and  promote their regeneration. Myelin helps conduct action potential down the axon faster than non-myelinated 
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This note was uploaded on 04/15/2008 for the course NEUROSCI 1306 taught by Professor Granados,keele,weaver,patton during the Spring '08 term at Baylor.

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Neuro2 - Neuroscience Dr D.G Neuron Physiology Neurons Similar to other somatic cells very distinctive and abundant in their variety of size shape

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