Neurons and Action Potentials Study Pack

Kibin's free study pack on Neurons and Action Potentials includes a 3-section study guide, 8 quiz questions, 10 flashcards, and 1 open-ended Explain review question. Sign up free to track your progress toward mastery, plus upload your own notes and recordings to create personalized study packs organized by course.

Last updated May 21, 2026

Topic mastery0%
Save progress →

Neurons and Action Potentials Study Guide

Trace the full journey of a nerve signal — from the resting membrane potential of −70 mV through depolarization, repolarization, and afterhyperpolarization — with this study pack on neurons and action potentials. Master the roles of voltage-gated Na⁺ and K⁺ channels, the sodium-potassium pump, refractory periods, and saltatory conduction along myelinated axons to ace your A&P exam.

Key Takeaways

  • •Neurons are electrically excitable cells that transmit information as brief voltage spikes called action potentials, generated by the sequential opening and closing of voltage-gated ion channels in the plasma membrane.
  • •At rest, a neuron maintains a membrane potential of approximately −70 mV (the resting membrane potential) through the combined effects of the sodium-potassium ATPase pump and selectively permeable leak channels.
  • •An action potential is triggered only when a depolarizing stimulus brings the membrane to the threshold potential of roughly −55 mV, causing rapid voltage-gated Na⁺ channels to open and Na⁺ to rush inward.
  • •Repolarization occurs when voltage-gated K⁺ channels open and K⁺ exits the cell, restoring the negative interior charge; a brief hyperpolarization (afterhyperpolarization) follows before the resting potential is reestablished.
  • •The absolute refractory period, during which no second action potential can fire regardless of stimulus strength, ensures that action potentials travel in only one direction along an axon.
  • •Conduction velocity depends on axon diameter and the presence of a myelin sheath; myelinated axons conduct signals rapidly via saltatory conduction, where the action potential jumps between Nodes of Ranvier.

Neuron Structure and the Basis of Electrical Signaling

Neurons are specialized cells built to receive, integrate, and transmit electrical signals over long distances, and their structure directly reflects each of those functions.

Anatomical Regions of a Neuron

  • •The cell body (soma) contains the nucleus and ribosomes and serves as the metabolic center of the neuron.
  • •Dendrites are short, branching extensions that receive incoming chemical signals from neighboring neurons at specialized contact points called synapses.
  • •The axon is a single, often long projection that conducts action potentials away from the soma toward a target cell; it terminates in axon terminals that release neurotransmitters.
  • •The axon hillock, the junction between the soma and axon, is the site where incoming signals are summed and an action potential is initiated if threshold is reached.

Functional Classification of Neurons

  • •Sensory (afferent) neurons carry signals from peripheral receptors toward the central nervous system.
  • •Motor (efferent) neurons carry commands from the central nervous system to muscles and glands.
  • •Interneurons reside entirely within the central nervous system and connect sensory and motor pathways.

Why Neurons Are Electrically Excitable

  • •The plasma membrane of a neuron contains embedded ion channel proteins that can open or close in response to changes in voltage, chemicals, or mechanical stretch.
  • •Because ions carry charge, any net movement of ions across the membrane changes the voltage difference between the inside and outside of the cell, which is measured as membrane potential in millivolts (mV).

Resting Membrane Potential: How Neurons Stay Polarized

Before any signal arrives, a neuron maintains a stable, negative interior voltage called the resting membrane potential, which is the electrical baseline from which all signaling departs.

Ion Distribution Across the Resting Membrane

  • •Sodium ions (Na⁺) are concentrated outside the cell at roughly 145 mM, while potassium ions (K⁺) are concentrated inside at roughly 140 mM; these gradients are maintained by the sodium-potassium ATPase (Na⁺/K⁺-ATPase) pump.
  • •The Na⁺/K⁺-ATPase actively transports 3 Na⁺ out of the cell and 2 K⁺ into the cell per ATP consumed, making it electrogenic and contributing a small negative charge to the interior.
  • •Large negatively charged proteins trapped inside the cell also contribute to the negative resting interior.

Role of Leak Channels in Setting −70 mV

  • •At rest, the membrane is far more permeable to K⁺ than to Na⁺ because potassium leak channels are open while most sodium channels remain closed.
  • •K⁺ diffuses outward down its concentration gradient, leaving behind negative charge; this outward leak continues until the electrical attraction pulling K⁺ back inward balances the concentration gradient, establishing an equilibrium near −70 mV.
  • •The Nernst equation can calculate the equilibrium potential for a single ion, while the Goldman equation accounts for the permeability of multiple ions simultaneously to predict the actual resting potential.

About this Study Pack

Created by Kibin to help students review key concepts, prepare for exams, and study more effectively. This Study Pack was checked for accuracy and curriculum alignment using authoritative educational sources. See sources below.

Sources

More in Anatomy & Physiology

See all topics →

Browse other courses

See all courses →