Electrical Signals Neurons

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Electrical Signals Neurons

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 4 Current Lecture Electrical Signals Neurons  Things to remember o Figure 8-1 (General organization of nervous system) o Fig 8-2,8-3,8-4 (Parts and general types of neurons) o Fig 8-5, 8-6 (Types and functions of glial cells)  Nature of neuronal signals o Neurons and muscle cells have electrical properties that are used to communicate information (generate signals) o ALL Living cells generate an electrical potential difference (Vm) across their plasma membranes (membrane potential) o Unlike most cells, neurons also generate signals, consisting of brief changes in Vm (membrane potential) o Signals make everything possible- Two types  Responses to a stimulus  Lowering of the membrane potential  Positive = upinside of cell is positive  Negative = downinside of cell is negative  1. Graded local signals  Graded- Amplitude varies with the strength of the stimulus  Local- signal generated in one place on the membrane, the amplitude decreases as it moves away from that one place  . All or non regenerative signals (action potential)  All or none = once you give a threshold stimulus, then it will be really positive really fast and this is called the action potential. All or none because if you give at least a threshold stimulus the action potential will always be the same size  Regenerative = As it spreads away, the amplitude does not decay with distance, keeps regenerating itself  Vm when one ion is permeable o Where do membrane potentials come from?- 2 conditions  1. Unequal distribution of an ion across the membrane  2. Plasma membrane must be permeable to the ions  rates of movement continue until they are equal and opposite (equilibrium)

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