Action Potential

Chapter 1: Introduction

• Welcome to human physiology topic focusing on neuroscience.

• Lecturer: Vladimir Zogodnyuk, contact via email for questions.

• Four lectures on:

  • Information spread in the nervous system.

  • Brain functions regarding perception, movement, and organ control.

• Recommended textbooks:

  • Silverton Human Physiology: Chapters 8, 9, 10, 11, 13.

  • Additional resources: Mastering A&P online.

  • Other textbooks: Purvis et al. Neuroscience, Beattel Neuroscience.

Chapter 2: Resting Membrane Potential

• Key Question:

  • What is resting membrane potential?

  • How is action potential generated?

  • Overview of synaptic transmission and ion channels.

• Neurons:

  • Process information, communicate with each other, and regulate body responses.

  • Dendrites receive information; axon transmits information.

• Approx. 100 billion neurons in CNS making vast connections.

Chapter 3: Resting Membrane Potential

• Neurons communicate via electrical and chemical signals.

• Cell membranes consist of phospholipid bilayer:

  • Uncharged substances pass easily.

  • Hydrophilic large molecules and ions need ion channels for transport.

• Resting membrane potential determined by:

  • Concentration gradients of ions.

  • Membrane permeability to ions.

Chapter 4: Potassium and Sodium

• Unequal distribution of ions across membrane.

• Concentration Gradients:

  • Potassium: Inside ~ 50 mmol, Outside ~ 5 mmol.

  • Sodium: Inside ~ 20 mmol, Outside ~ 145 mmol.

• Diffusion: Movement from high to low concentration.

• Sodium-potassium pump maintains these gradients through active transport.

Chapter 5: Ions of Potassium

• Active transport exchanges 2 potassium ions in for 3 sodium ions out.

• Potassium leak channels allow diffusion of potassium:

  • Creates an electrical gradient as potassium leaves the cell.

• Balance between diffusional and electrical forces leads to equilibrium.

Chapter 6: Concentration of Potassium

• Equilibrium potential: potential at which ions move equally in both directions.

• Nernst equation used to calculate equilibrium potential for potassium.

• Example calculation results in approximately -90 mV equilibrium potential for potassium.

Chapter 7: Resting Membrane Potential

• Resting membrane potential of neuron closely aligns with equilibrium potential for potassium.

• Neuron at rest primarily permeable to potassium, with some permeability to chloride and sodium.

• Higher permeability for potassium compared to sodium and chloride.

Chapter 8: Resting Membrane Potential

• Calculated resting membrane potential approximately -70 mV.

• Nernst equation applies to other ions like sodium, chloride, and calcium:

  • Sodium: +50 mV, Calcium: +120 mV, Chloride: -80 mV.

• Ion movement through channels alters membrane potential, used as signals in neuron communication.

Chapter 9: Graded Potential

• Depolarization: positive change; increases excitability.

• Hyperpolarization: negative change; decreases excitability.

• Graded potentials initiated by electrical stimulation or neurotransmitter activation.

Chapter 10: Conclusion

• Membrane potential significantly affects ion movements:

  • At rest, small force for potassium, larger for sodium.

• Depolarization leads to larger forces for ion movement.