Electrochemical Gradient
- Intracellular vs extracellular ion concentrations differ
- This difference creates an electrochemical gradient across the membrane
Ohm’s Law
Relationship between membrane potential and ionic currents
Ohm’s Law equation
V=IR
Voltage = (Current)(Resistance)
Ion Channels
- Large, transmembrane proteins that allow ions to enter or exit cells
- Generally down there concentration gradient
4 types of ion channels
- Voltage-gated
- Chemically gated
- Mechanically gated
- Thermally gated
Voltage-gated ion channels
- Open/close in response to voltage changes across membrane
- Selectivity filter allows only specific ions
Chemically gated ion channels
- Open when a ligand interacts with it
- Found in dendrites of neurons
Mechanically gated ion channels
Open in response to mechanical deformations such as stretch
Thermally gated ion channels
- Respond to changes in temperature
- Present in specialized neurons that project to the skin to act as temperature detectors
Resting membrane potential (RMP)
Electrical potential across the cells membrane
Depolarization
membrane potential moves closer to 0 mV (less negative)
Repolarization
After depolarization or hyperpolarization, membrane potential returns toward RMP
Hyperpolarization
Membrane potential becomes more negative than RMP
Graded potentials
Local changes in membrane potential that are used for short distance signalling
Spread of Depolarization
- Graded potentials start locally but spread along membrane
- Spread happens by current flow, not ion diffusion
Graded Potentials & Current Loss
- Graded potentials weaken as they spread, lose charge over distance
- Short-lived
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Module 1: Section 1 + 256
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Module 1: Section 316
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Module 1: Section 413
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Module 1: Section 531
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Module 2: Section 120
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Module 2: Section 216
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Module 2: Section 332
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Module 2: Section 451
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Module 2: Section 511
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Module 4: Section 127
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Module 4: Section 235
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Module 4: Section 333
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Module 4: Section 426
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Module 4: Section 59
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Module 4: Section 628
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Module 5: Section 115
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Module 5: Section 234
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Module 5: Section 352
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Module 5: Section 47
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Module 5: Section 533
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Module 5: Section 67
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Module 6: Section 121
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Module 6: Section 223
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Module 6: Section 344
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Module 6: Section 428
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Module 6: Section 512
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Module 6: Section 613
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Module 6: Section 743
