Chapter 11 – Fundamentals of the Nervous System and Nervous Tissue

Vocabulary flashcards covering key terms and definitions from Chapter 11 on nervous system fundamentals, neuroglia, neurons, electrical properties, signaling, synapses, neurotransmitters, neural circuits, and development.

Nervous System

Master controlling and communicating system of the body that uses electrical and chemical signals.

Sensory Input

Information gathered by sensory receptors about internal and external changes.

Integration

Processing and interpretation of sensory input by the CNS.

Motor Output

Activation of effector organs (muscles and glands) that produces a response.

Central Nervous System (CNS)

Brain and spinal cord; integration and control centers.

Peripheral Nervous System (PNS)

Nerves and ganglia outside the CNS; communication lines between the CNS and the rest of the body.

Afferent (Sensory) Division

PNS subdivision that carries impulses toward the CNS.

Efferent (Motor) Division

PNS subdivision that transmits impulses from the CNS to effector organs.

Somatic Nervous System

Voluntary motor division that conducts impulses to skeletal muscles.

Autonomic Nervous System (ANS)

Involuntary motor division regulating cardiac muscle, smooth muscle, and glands.

Sympathetic Division

ANS subdivision that mobilizes body systems during activity (fight or flight).

Parasympathetic Division

ANS subdivision that conserves energy and promotes housekeeping during rest.

Neuroglia (Glial Cells)

Supporting cells of nervous tissue that nourish, protect, and insulate neurons.

Astrocytes

Most abundant CNS glia; support neurons, regulate exchanges with capillaries, guide migration, and participate in information processing.

Microglial Cells

CNS immune defense cells that transform into phagocytes in response to injury.

Ependymal Cells

Ciliated CNS glia lining brain ventricles and spinal canal; circulate cerebrospinal fluid.

Oligodendrocytes

CNS glia whose processes form myelin sheaths around multiple axons.

Satellite Cells

PNS glia that surround neuron cell bodies in ganglia; similar to astrocytes.

Schwann Cells

PNS glia that form myelin sheaths around peripheral nerve fibers and aid regeneration.

Neuron

Excitable cell that generates and transmits nerve impulses; structural unit of the nervous system.

Soma (Perikaryon/Cell Body)

Biosynthetic center of a neuron containing nucleus, organelles, and Nissl bodies.

Dendrite

Receptive, branched neuron process that conveys graded potentials toward the cell body.

Axon

Conducting neuron process that generates nerve impulses and transmits them away from the soma.

Axon Hillock

Cone-shaped region of soma where action potentials are initiated.

Axon Terminal (Terminal Bouton)

Distal secretory region of an axon that releases neurotransmitters.

Myelin Sheath

Lipid-rich wrapping that insulates axons and increases impulse conduction speed.

Node of Ranvier (Myelin Sheath Gap)

Gap between adjacent myelinating cells where ion channels are concentrated.

White Matter

Regions of CNS containing dense collections of myelinated fibers.

Gray Matter

Regions of CNS with neuron cell bodies and unmyelinated fibers.

Multipolar Neuron

Neuron with one axon and many dendrites; most common in CNS.

Bipolar Neuron

Neuron with one axon and one dendrite; found in retina and olfactory mucosa.

Unipolar (Pseudounipolar) Neuron

Neuron with a single process that splits into peripheral and central branches; sensory neurons in PNS.

Sensory (Afferent) Neuron

Carries impulses from receptors toward the CNS; mainly unipolar.

Motor (Efferent) Neuron

Transmits impulses from CNS to effectors; multipolar.

Interneuron (Association Neuron)

Neuron located within CNS that processes and relays information; 99% of all neurons.

Resting Membrane Potential

Approximately –70 mV charge difference across a neuron's membrane when not firing.

Voltage

Electrical potential energy due to separated charges; measured in volts.

Current

Flow of electrical charge (ions) between two points.

Resistance

Hindrance to charge flow; high in insulators, low in conductors.

Ohm’s Law

Relationship I = V/R linking current, voltage, and resistance.

Leakage Channel

Always-open ion channel allowing passive ion movement.

Gated Ion Channel

Protein channel that opens or closes in response to specific stimuli (chemical, voltage, mechanical).

Depolarization

Decrease in membrane potential making the interior less negative.

Hyperpolarization

Increase in membrane potential making the interior more negative.

Graded Potential

Short-lived, localized change in membrane potential that decays with distance.

Action Potential

Brief, large depolarization that propagates along axons without diminishing; nerve impulse.

Threshold

Membrane potential (≈ –55 mV) at which an action potential is triggered.

Absolute Refractory Period

Time during which a neuron cannot fire another action potential, ensuring one-way transmission.

Relative Refractory Period

Interval after absolute refractory when a stronger-than-normal stimulus can trigger an AP.

Continuous Conduction

Slow AP propagation in unmyelinated axons where every part of membrane depolarizes.

Saltatory Conduction

Fast AP propagation in myelinated axons where impulses jump node to node.

Group A Fibers

Large-diameter, myelinated fibers conducting at ~150 m/s; somatic motor and sensory.

Group B Fibers

Intermediate diameter, lightly myelinated fibers conducting at ~15 m/s.

Group C Fibers

Small diameter, unmyelinated fibers conducting at ~1 m/s.

Synapse

Functional junction where information is transferred from one neuron (or cell) to another.

Presynaptic Neuron

Neuron that conducts impulses toward a synapse.

Postsynaptic Neuron

Neuron or effector cell receiving information at a synapse.

Chemical Synapse

Most common synapse type that uses neurotransmitters across a synaptic cleft.

Electrical Synapse

Synapse where ions flow directly through gap junctions for rapid communication.

Excitatory Postsynaptic Potential (EPSP)

Graded depolarization of postsynaptic membrane that increases likelihood of AP.

Inhibitory Postsynaptic Potential (IPSP)

Graded hyperpolarization that decreases likelihood of AP.

Temporal Summation

Addition of EPSPs/IPSPs from rapid, successive firing of one presynaptic neuron.

Spatial Summation

Addition of potentials from multiple presynaptic neurons firing simultaneously.

Synaptic Potentiation

Enhanced synaptic strength following repeated activity; basis of learning and memory.

Presynaptic Inhibition

Reduction of neurotransmitter release via an axoaxonal synapse.

Acetylcholine (ACh)

First identified neurotransmitter; excitatory at skeletal NMJ, inhibitory in heart; degraded by AChE.

Dopamine

Catecholamine involved in reward, motivation, and motor control; imbalance linked to Parkinson’s.

Norepinephrine (NE)

Catecholamine neurotransmitter and hormone; key in alertness and ANS activity.

Serotonin

Indolamine affecting mood, appetite, and sleep; synthesized from tryptophan.

Gamma-Aminobutyric Acid (GABA)

Primary inhibitory amino-acid neurotransmitter in the brain.

Glutamate

Major excitatory amino-acid neurotransmitter in the CNS.

Substance P

Peptide neurotransmitter that mediates pain signals.

Endorphins

Peptide neurotransmitters acting as natural opiates to reduce pain perception.

Nitric Oxide (NO)

Gaseous neurotransmitter involved in learning, memory, and vasodilation.

Endocannabinoids

Lipid neurotransmitters that bind THC receptors; roles in appetite, memory, and nausea control.

Direct Neurotransmitter Action

Neurotransmitter binds to and opens ion channels for rapid effects.

Indirect Neurotransmitter Action

Neurotransmitter acts through second messengers for prolonged effects.

Neuromodulator

Chemical messenger that modifies synaptic transmission strength without directly causing EPSP/IPSP.

Channel-Linked Receptor

Ligand-gated ion channel producing immediate, brief synaptic responses.

G Protein–Linked Receptor

Metabotropic receptor activating second-messenger pathways for slow, prolonged responses.

Neuronal Pool

Functional group of interneurons that integrate information and forward it to destinations.

Discharge Zone

Central region of a neuronal pool where neurons reach threshold easily.

Facilitated Zone

Peripheral region of pool requiring additional stimuli to reach threshold.

Diverging Circuit

Neuronal circuit where one input leads to many outputs; amplifying.

Converging Circuit

Circuit where many inputs converge to one output; concentrating.

Reverberating Circuit

Oscillating circuit in which impulses echo through a feedback loop (e.g., breathing).

Parallel After-Discharge Circuit

Circuit with parallel pathways converging on one output cell, producing after-discharge bursts.

Growth Cone

Dynamic, motile tip of a growing axon that seeks its synaptic target during development.

Synaptic Pruning

Developmental process where unused synapses are eliminated to refine neural circuits.