Foundations of Neuroscience

Citation

Henley, C. (2021). Foundations of Neuroscience. Michigan State University Libraries. Free official edition: https://openbooks.lib.msu.edu/neuroscience/

Chapter Summary

The book is organized into seven parts made up of 40 short, single-concept chapters; closely related chapters are grouped here by part, with the book's chapter titles kept exactly.

Part 1 – Neuron Structure & Function: The Neuron; Ion Movement; Membrane Potential; The Membrane at Rest; Postsynaptic Potentials; Action Potentials; Voltage Clamp

The opening part builds the electrical neuron step by step. It starts with the parts of a neuron (dendrites, cell body, axon hillock, myelinated axon, presynaptic terminal) and how structure varies with function, then explains why ions cannot cross the lipid bilayer without channels and how concentration and electrical gradients combine into an electrochemical driving force. The Nernst equation is introduced with a worked calculation of sodium's equilibrium potential (about +60 mV), and the Goldman equation explains why the resting potential sits near −65 mV, close to potassium's equilibrium potential, with the sodium–potassium pump maintaining the gradients. Later chapters cover excitatory and inhibitory postsynaptic potentials and their temporal and spatial summation, the phases of the action potential driven by voltage-gated sodium and potassium channels, conduction speed, refractory periods and firing-rate coding, and finally the voltage clamp experiment that revealed these currents.

Part 2 – Neuronal Communication: Synapse Structure; Neurotransmitter Synthesis and Storage; Neurotransmitter Release; Neurotransmitter Action: Ionotropic Receptors; Neurotransmitter Action: G-Protein-Coupled Receptors; Neurotransmitter Clearance; Drug and Toxin Effects; Epigenetics

This part follows a chemical signal across the synapse. It contrasts electrical synapses (gap junctions) with chemical synapses, sets out the criteria for calling a molecule a neurotransmitter, and traces the synthesis and storage of acetylcholine, glutamate, GABA, glycine, the monoamines and neuropeptides. Release is explained through calcium entry, active zones, SNARE proteins and synaptotagmin. Two receptor chapters contrast fast ionotropic receptors (AMPA, NMDA, nicotinic, GABA and glycine receptors, with the concept of reversal potential) and slower G-protein-coupled receptors with their cAMP and phospholipase C cascades and signal amplification. The part closes with how transmitter action is ended (reuptake, glial uptake, enzymatic breakdown), how drugs and toxins act at each step, and a short introduction to gene transcription and epigenetic changes such as DNA methylation and histone acetylation.

Part 3 – Nervous System Organization: Anatomical Terminology; External Brain Anatomy; Internal Brain Anatomy; Brainstem and Spinal Cord

The anatomy part supplies the vocabulary used later: directional terms and planes of section, the central and peripheral divisions, and afferent versus efferent signals. It then surveys the lobes of the cerebral cortex and their main functions, gyri and sulci, the cerebellum and brainstem, and internal structures visible in sagittal and coronal sections (thalamus and hypothalamus, corpus callosum, amygdala, hippocampus, basal ganglia, ventricles). A final chapter describes the midbrain, pons and medulla, the cranial nerves and the organization of grey and white matter in the spinal cord.

Part 4 – Sensory Systems: General Principles of Sensory Systems; Vision: The Retina; Vision: Central Processing; Somatosensory Systems; Touch: The Skin; Touch: Central Processing; Pain, Temperature, and Itch; Taste

After a brief chapter on shared principles (transduction, receptor potentials, receptive fields, lateral inhibition, labelled-line and population coding, the thalamus as relay), this part covers three senses in detail, as the introduction notes. Vision runs from retinal anatomy and phototransduction through ON and OFF bipolar cells and centre–surround receptive fields to the optic chiasm, the lateral geniculate nucleus, primary visual cortex and the dorsal ("where") and ventral ("what") streams. The somatosensory chapters treat dorsal root ganglion neurons, afferent fibre types and dermatomes; mechanoreceptors, receptive-field size and adaptation; the dorsal column–medial lemniscus and trigeminal pathways, the somatotopic map and cortical plasticity; and nociception, first and second pain, sensitization, pain modulation, temperature and itch. Taste covers the five basic tastes, their transduction mechanisms, coding and central pathway.

Part 5 – Motor System: Spinal Control of Movement; Planning of Movement; Basal Ganglia; Execution of Movement

The motor part works from the bottom up: alpha motor neurons and the neuromuscular junction, stretch, withdrawal and crossed-extensor reflexes, and central pattern generators for locomotion. It then moves to planning in posterior parietal, prefrontal and premotor cortex, the direct and indirect pathways of the basal ganglia and the idea of disinhibition (with links to Parkinson's and Huntington's diseases), and execution by the primary motor cortex using population coding, with lateral and ventromedial descending tracts.

Part 6 – Neuroendocrine Systems: HPA Axis; Neural Control of Stress; HPG Axis; Sexual Differentiation; Masculinizing Effects of Estrogen; Social Bonding

These shorter chapters explain how the hypothalamus controls hormone release. The HPA axis chapter follows CRH, ACTH and cortisol with negative feedback and chronic stress; a companion chapter shows how the amygdala, hippocampus and prefrontal cortex regulate the stress response. The HPG axis, chromosomal and gonadal sex, organizational and activational hormone effects, the conversion of testosterone to estradiol by aromatase, and the roles of posterior pituitary hormones in pair and parental bonding complete the part. The sexual differentiation chapter notes that it uses a male/female binary for teaching while recognizing that sex and gender exist on a continuum.

Part 7 – Behavioral Neuroscience: Motivation and Reward; Studying Fear; Post-Traumatic Stress Disorder

The final part is brief. It describes the dopamine reward circuit from the ventral tegmental area to the nucleus accumbens and prefrontal cortex, self-stimulation experiments, reward prediction and drugs of abuse; laboratory models of learned fear (fear conditioning and conditioned defeat); and post-traumatic stress disorder, its causes, symptoms and nervous-system dysfunction.

Key Concepts

Part 1 – Neuron Structure & Function

• Electrochemical gradient: the combined push of concentration and electrical gradients that determines which way an ion flows through an open channel.
• Equilibrium potential and the Nernst equation: the membrane potential at which an ion's two gradients balance, calculated from its inside and outside concentrations.
• Resting membrane potential: about −65 mV, set mainly by potassium permeability and described by the Goldman equation.
• Action potential: a brief reversal of membrane potential produced by voltage-gated sodium and potassium channels, sped up by myelin and larger axon diameter.

Part 2 – Neuronal Communication

• Chemical versus electrical synapse: transmission by released neurotransmitter across a cleft versus direct ion flow through gap junctions.
• Ionotropic receptor: a ligand-gated channel producing fast postsynaptic potentials, characterized by its reversal potential.
• G-protein-coupled receptor: a metabotropic receptor that triggers second-messenger cascades with slower, amplified and longer-lasting effects.
• Epigenetic modification: chemical changes to DNA or histones, such as methylation and acetylation, that alter how readily genes are transcribed.

Part 3 – Nervous System Organization

• Directional terms and planes: dorsal/ventral, rostral/caudal and the sagittal, coronal and horizontal planes used to locate brain structures.
• CNS and PNS: brain and spinal cord versus cranial and spinal nerves.
• Cranial nerves: the nerves that enter and leave the brain, mostly through the brainstem.

Part 4 – Sensory Systems

• Sensory transduction: conversion of a physical or chemical stimulus into electrical signals by specialized receptors.
• Receptive field and lateral inhibition: the region in which a stimulus affects a neuron, and inhibition between neighbours that sharpens edges and contrast.
• Dorsal and ventral visual streams: parallel cortical pathways for spatial location and object identity.
• Somatotopic map: the orderly representation of the body surface in primary somatosensory cortex.

Part 5 – Motor System

• Spinal reflexes and central pattern generators: movement controlled within the spinal cord without input from the brain.
• Direct and indirect pathways: basal ganglia circuits that facilitate or suppress movement through disinhibition of the thalamus.
• Population coding: movement direction encoded by the combined activity of many motor cortex neurons.

Part 6 – Neuroendocrine Systems

• HPA axis: the hypothalamic–pituitary–adrenal hormone cascade (CRH, ACTH, cortisol) with negative feedback.
• Organizational versus activational effects: long-lasting hormone effects during critical developmental periods versus short-term effects in adulthood.
• Aromatization: conversion of testosterone to estradiol, which in some species masculinizes the brain.

Part 7 – Behavioral Neuroscience

• Reward circuit: dopamine release from the ventral tegmental area into the nucleus accumbens and prefrontal cortex.
• Fear conditioning: pairing a neutral stimulus with an aversive one to study learned fear.

Critical Analysis

Strengths

• One concept per chapter. The introduction commits to short chapters that each focus on a single idea, following Universal Design for Learning. Most chapters run to roughly 1,000–3,000 words and use the same layout: a short overview, the main text, a conclusion, Key Takeaways, Important Terms with pop-up definitions, a "Test Yourself!" interactive quiz and a video lecture.
• Strong visual and multimedia support. Original figures and animations (for example of sodium gradients and action potential propagation) accompany the text, and detailed alternative text is provided for images and animations, which makes the book unusually accessible.
• Quantitative membrane physiology done carefully. The Nernst and Goldman equations are worked through with concrete ion concentrations, and later chapters reuse the same values (for example in reversal potentials and the voltage clamp), so students practise prediction rather than memorization. Quiz questions ask students to calculate equilibrium potentials for a hypothetical "Thinking Cell".
• Clear sequencing. Each part builds on the previous one: membrane physiology prepares for synaptic transmission, receptor signalling for drug effects and epigenetics, and anatomy for the sensory and motor pathways.

Limitations

• Deliberately limited scope. The introduction states that the first edition follows a Michigan State neurobiology course and covers only three sensory systems; hearing, balance and smell, as well as learning and memory, sleep, language and development, are not treated as topics in their own right.
• Uneven depth at the end. The neuroendocrine and behavioural parts are much shorter (several chapters are under 1,000 words), and some, such as Social Bonding and Post-Traumatic Stress Disorder, lack the Key Takeaways and quiz found elsewhere.
• Little on research methods or clinical detail. Apart from the voltage clamp, experimental techniques (imaging, electrophysiology recording methods, lesion and genetic approaches) and neurological disorders receive only passing mention.
• A living web text. The site is updated over time, so chapter numbering and content may differ from what other readers or citations refer to; the book is best used online, where the quizzes and animations work.

Where It Fits in the Course

For a neuroscience course this is an entry-level text. Bear, Connors and Paradiso's Neuroscience: Exploring the Brain is described as a comprehensive introductory textbook covering a broader set of systems; Purves and colleagues' Neuroscience and Liqun Luo's Principles of Neurobiology (both fuller undergraduate textbooks) go further into mechanisms and experimental evidence; Nicholls and colleagues' From Neuron to Brain (a graduate-level text) treats cellular neurophysiology in depth; and Dayan and Abbott's Theoretical Neuroscience is a mathematical modelling text.

Henley's book is a good first read or a free companion to one of the larger textbooks. Its Part 1 on membrane potentials and action potentials, with worked Nernst and Goldman calculations, prepares students for the quantitative cellular chapters of Purves or Nicholls et al., and its short sensory and motor chapters can be read before the fuller treatments in Bear et al. or Purves. Students heading for Dayan and Abbott will need much more mathematics than this book provides.

How to Use This Book

The book is aimed at undergraduates new to neuroscience. Introductory biology is enough for most of it; a little chemistry (ions, concentration, logarithms for the Nernst equation) helps with Part 1.

Read Parts 1 and 2 in order, since everything else depends on them, and do the Nernst and Goldman examples by hand. Use Part 3 as a reference for anatomical terms while reading Parts 4 and 5. Parts 6 and 7 are short and can be read as introductions to neuroendocrinology and behavioural neuroscience, to be supplemented from a fuller textbook. For each chapter, watch the video lecture or read the text, then take the "Test Yourself!" quiz more than once (it draws different questions), check the Important Terms pop-ups, and revise from the Key Takeaways. The animations are worth replaying for the dynamic topics: action potential propagation, transmitter release and second-messenger cascades.

Edition and Sources

This guide is based on the free official online edition of Foundations of Neuroscience by Casey Henley, published by Michigan State University Libraries (copyright 2021, CC BY-NC-SA 4.0) at https://openbooks.lib.msu.edu/neuroscience/, read through the site's Pressbooks interface as available in October 2026. It draws on the introduction and book description, the full table of contents, and all 40 chapters (every section heading, each chapter's opening overview, and all Key Takeaways), with the Membrane Potential chapter, including its worked Nernst calculations, Important Terms and quiz items, read in full.