BIOS 281 Lecture 3 Membrane Transport and Potentials

there are also large nega vely charged proteins that

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Unformatted text preview: electrochemical gradient. –  Ions move from areas of higher concentra0on to areas of lower concentra0on - the “chemical” (concentra0on) part of the gradient. –  Posi0vely charged ca0ons move toward a nega0vely charged area, and nega0vely charged anions move toward a posi0vely charged area - the electrical aspect of the gradient. Electrical Signals in Neurons •  Ac0ve channels open in response to a s0mulus (they are “gated”). There are 3 types of ac-ve, gated channels: –  Ligand- gated channels respond to a neurotransmiher and are mainly concentrated at the synapse. –  Voltage- gated channels respond to changes in the transmembrane electrical poten0al and are mainly located along the neuronal axon. –  Mechanically- gated channels respond to mechanical deforma0on (applying pressure to a receptor). •  “Leakage” channels are also gated but they are not ac0ve, and they open and close randomly. Maintaining the RMP •  A neuron’s RMP is measured at rest, when it is not conduc0ng a nerve impulse. –  The res0ng membrane poten0al exists because of a small buildup of nega0ve ions in the cytosol along the inside of the membrane, and an equal buildup of posi0ve ions in the extracellular fluid along the outside surface of the membrane. The buildup of charge occurs only very close to the membrane – the cytosol elsewhere in the cell is electrically neutral. Maintaining the RMP •  The RMP is slightly nega0ve because leakage channels favor a gradient where more K+ leaks + + out, than Na leaks in (there are more K channels than Na+ channels.) –  There are also large nega-vely charged proteins that always remain in the cytosol. Maintaining the RMP Interac(ons Anima(on •  In neurons, a typical value for the RMP is –70 mV (the minus sign indicates that...
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This note was uploaded on 11/12/2013 for the course BIOS 281 taught by Professor Varamini during the Fall '12 term at Biola University.

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