Neuro Key Terms

Key Figures in Neuroscience

  • Franz Joseph Gall – Developed phrenology, linking brain areas to traits.

  • Jean Pierre Flourens – Used ablation studies to disprove phrenology, showing brain function is distributed.

  • Paul Broca – Identified Broca’s area, crucial for speech production.

  • Korbinian Brodmann – Mapped the cortex into Brodmann areas based on cellular structure and function.

Neuron Doctrine vs. Reticular Theory

Reticular Theory (Golgi)

Neuron Doctrine (Ramón y Cajal)

Neurons form a continuous nerve net.

Neurons are individual cells that communicate at synapses.

Communication is bi-directional.

Communication is unidirectional (dendrites → axon).

Disproven by modern neuroscience.

True theory of neural communication.

Parts of a Neuron

  • Dendrites – Receive signals from other neurons.

  • Soma (Cell Body) – Contains the nucleus; controls metabolism and protein synthesis.

  • Axon – Transmits signals; action potentials begin at the axon hillock.

  • Axon Terminal – Releases neurotransmitters to communicate with the next neuron.

Neurons vs. Glial Cells

  • Neurons – Primary communicators of the nervous system.

  • Glia – Support and protect neurons; make up 90% of brain cells.

Type of Glial Cell

Function

Astrocytes

Maintain blood-brain barrier, respond to injury by forming scar tissue.

Oligodendrocytes

Myelinate CNS axons (one oligodendrocyte myelinates multiple axons).

Schwann Cells

Myelinate PNS axons (one Schwann cell per axon).

Ependymal Cells

Line ventricles, produce cerebrospinal fluid (CSF).

Microglia

Act as the immune system of the CNS, removing debris and responding to injury.

Chapter 3: Resting Membrane Potential & Action Potentials

Key Ions & Their Roles

Ion

Higher Concentration

Function

Sodium (Na⁺)

Outside

Drives depolarization; enters during action potential.

Potassium (K⁺)

Inside

Maintains resting potential; exits during repolarization.

Calcium (Ca²⁺)

Outside

Triggers neurotransmitter release at synapse.

Chloride (Cl⁻)

Outside

Helps regulate excitability by stabilizing membrane potential.

Membrane Potential (Vm)

  • The electrical potential difference between the inside and outside of a neuron.

  • Resting Membrane Potential (RMP) ≈ -65mV

    • Inside of the neuron is negative due to large proteins and K⁺ retention.

    • Outside of the neuron is positive, mainly due to Na⁺.

Key Concepts in Ion Transport

  • Concentration Gradient – Ions move from high to low concentration.

  • Electrical Gradient – Ions move toward opposite charges.

  • Electrochemical Gradient – Combination of concentration + electrical forces.

  • Lipid Bilayer – The neuron’s membrane; prevents ion movement without channels.

Ion Channels & Transporters

Type

Function

Leak Channels

Always open; maintain resting membrane potential.

Ion Channels

Selectively allow ions to pass through the membrane.

Sodium-Potassium Pump (Na⁺/K⁺ Pump)

Uses ATP to actively transport 3 Na⁺ out, 2 K⁺ in.

Key Equations

  • Equilibrium Potential (Eion) – Voltage at which the net movement of an ion stops.

  • Nernst Equation – Calculates Eion for a single ion based on concentration.

  • Goldman Equation – Calculates resting membrane potential (Vm) considering multiple ions.

  • Driving Force – The difference between the membrane potential (Vm) and an ion’s equilibrium potential (Eion):

    • Negative Driving Force → Ion moves into the cell.

    • Positive Driving Force → Ion moves out of the cell.

Action Potential & Signal Propagation

Action Potential Stages

  1. Resting State (-65mV) – Neuron at baseline potential.

  2. Depolarization – Na⁺ enters the cell; membrane potential becomes positive.

  3. Repolarization – K⁺ leaves the cell; membrane potential returns negative.

  4. Hyperpolarization – Too much K⁺ exits, causing a brief dip below resting potential.

Where Action Potentials Begin

  • Spike Initiation Zone – Located at the axon hillock, where action potentials start if depolarization reaches threshold.

Factors Affecting Signal Speed

  • Axonal Diameter – Larger diameter → faster conduction.

  • Myelination – Insulation that speeds up signals.

Saltatory Conduction

  • Action potentials "jump" between Nodes of Ranvier, speeding up signal transmission.

  • Nodes of Ranvier – Gaps in myelin where voltage-gated Na⁺ channels regenerate the action potential.

Neurological Disorders & Neuronal Structure

Condition

Effect on Neurons

Alzheimer’s Disease

Tau protein destabilizes microtubules, leading to neurodegeneration.

Chronic Traumatic Encephalopathy (CTE)

Microtubule misalignment from repeated brain trauma; accumulation of tau.

Wallerian Degeneration

Axon damage leads to degeneration and death.

Multiple Sclerosis (MS)

Autoimmune attack on CNS myelin; slows down conduction.

Charcot-Marie-Tooth Disease

Genetic disorder affecting PNS myelin, causing muscle weakness.

Final Notes: "A Neuron at Rest is a Banana in Salty Milk!" 🍌🥛

  • Inside the neuron (like a banana) → Full of K⁺

  • Outside the neuron (like salty milk) → Full of Na⁺, Cl⁻, Ca²⁺

  • Resting Potential (-65mV) – More negative inside, positive outside

  • Na⁺/K⁺ Pump maintains this balance by removing 3 Na⁺ and bringing in 2 K⁺

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