Study Guide: Lecture I

Ionic Composition of Nerve Cells

Refers to the similarity of ionic composition between the extracellular and intracellular fluids in the brain, akin to seawater.

Key Ions

Important ions in nerve cells: Sodium (Na+), Potassium (K+), Chloride (Cl-), Anions (A-).

Nernst Equation

An equation that calculates the equilibrium potential (Eion) for a specific ion, determining membrane potential at which there's no net movement of that ion.

Equilibrium Potential (Eion)

The membrane potential at which there is no net movement of a specific ion across the membrane.

Sodium-Potassium Pump

An active transport mechanism that pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, maintaining ion gradients.

Resting Membrane Potential (Em)

The voltage difference across a neuronal membrane when the neuron is at rest, influenced by the permeability of different ions.

Astrocytes

A type of glial cell that provides support to neurons and regulates the extracellular environment.

Tripartite Synapse

The concept that astrocytes, presynaptic and postsynaptic neurons work together within a synapse.

Potassium Syphoning

The process by which astrocytes regulate extracellular potassium (K+) levels to maintain neuronal excitability.

Length Constant (λ)

Defines how far a graded potential will passively travel along an axon, influenced by membrane resistance and internal/external resistances.

Time Constant (τ)

The time required for the membrane potential to reach 63% of its final value during a current injection.

Passive Membrane Properties

Characteristics of neurons influencing signal propagation such as spatial decay, which describes how graded potential dissipates.

Active Transport

The movement of solutes against their concentration gradient using energy and active proteins.

Ionic Gradients

Differences in concentration of ions between extracellular and intracellular fluids critical for electrical signaling in neurons.

Electrochemical Gradient

A gradient that encompasses both the concentration and electrical gradient influencing ion movement across membranes.

Glial Cells

Supportive cells in the nervous system that control synaptic transmission and extracellular ion concentrations.

Mechanisms of Ion Transport

Methods by which ions move across the neuronal membrane: simple diffusion, channel-mediated diffusion, carrier-mediated diffusion, and active transport.