Introduction to the Nervous System Unit

Introduction to Electrophysiology of Neurons

• Focus on how neurons send electrical signals and communicate.

Concentration Gradients

• More sodium ions ( ext{Na}^+) are present outside the neuron than inside.

• Sodium ions move into the neuron through ion channels due to the concentration gradient.

Membrane Potential and Equilibrium

• Membrane Potential (Vm): Voltage inside the cell compared to outside.

• Equilibrium Potential: Voltage where specific ions are in balance.

  • Sodium's equilibrium potential: approximately +60 mV.

  • Potassium's equilibrium potential: approximately -90 mV.

• At rest, the neuron has a membrane potential of about -70 mV.

Resting Potential

• At rest, the neuron is more affected by potassium due to more potassium channels being open than sodium.

  • Potassium's tendency to leak out results in a slightly negative resting membrane potential.

Ion Channels

• Leak Channels:

  • More sodium leak channels than potassium, affecting the resting membrane potential.

• Ligand-Gated Ion Channels: Activated by neurotransmitters, leading to graded potentials.

Ion Movement

• Depolarization: Positive ion (sodium) entering the cell, making the membrane potential less negative.

• Hyperpolarization: Positive ion (potassium) leaving the cell, making the membrane potential more negative.

Local Potentials (Graded Potentials)

• Small changes in membrane potential (10-15 mV).

• Can be