Fundamentals of the Nervous System and Nervous Tissue – Key Vocabulary

A comprehensive set of vocabulary flashcards covering major terms and concepts from Chapter 11: Fundamentals of the Nervous System and Nervous Tissue.

Nervous System

The master controlling and communicating system of the body that uses rapid electrical and chemical signals.

Central Nervous System (CNS)

Comprises the brain and spinal cord; acts as the integration and control center.

Peripheral Nervous System (PNS)

All nervous tissue outside the CNS; mainly cranial and spinal nerves that link the body to the CNS.

Sensory (Afferent) Division

PNS subdivision that carries impulses from sensory receptors to the CNS.

Somatic Sensory Fibers

Afferent fibers conveying impulses from skin, skeletal muscles, and joints to the CNS.

Visceral Sensory Fibers

Afferent fibers carrying impulses from visceral organs to the CNS.

Motor (Efferent) Division

PNS subdivision that transmits impulses from the CNS to effector organs (muscles and glands).

Somatic Nervous System

Motor system conducting impulses from the CNS to skeletal muscles; under voluntary control.

Autonomic Nervous System (ANS)

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

Sympathetic Division

ANS branch that mobilizes body systems during activity ("fight-or-flight").

Parasympathetic Division

ANS branch that promotes housekeeping functions during rest ("rest-and-digest").

Neuroglia (Glial Cells)

Supporting cells that protect, nourish, and insulate neurons.

Astrocytes

Most abundant CNS glial cells; support neurons and regulate exchanges with blood capillaries.

Microglial Cells

Small CNS glia that monitor neuron health and act as phagocytes.

Ependymal Cells

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

Oligodendrocytes

Branched CNS glia that form myelin sheaths around CNS nerve fibers.

Satellite Cells

PNS glia surrounding neuron cell bodies; function like astrocytes.

Schwann Cells

PNS glia that myelinate peripheral axons and aid regeneration.

Neuron

Excitable cell that transmits electrical signals; structural unit of the nervous system.

Dendrite

Receptive neuron process conveying graded potentials toward the cell body.

Axon

Conducting neuron process that carries action potentials away from the cell body.

Axon Hillock

Cone-shaped region of the cell body where the axon originates.

Myelin Sheath

Whitish, lipid-protein covering that electrically insulates axons and speeds impulse conduction.

Node of Ranvier (Myelin Sheath Gap)

Gap between adjacent myelin segments where axon collaterals may emerge.

White Matter

Regions of CNS containing dense collections of myelinated fibers.

Gray Matter

CNS areas consisting mainly of neuron cell bodies and unmyelinated fibers.

Multipolar Neuron

Neuron with one axon and two or more dendrites; most common type.

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; mainly sensory.

Sensory Neuron

Neuron transmitting impulses toward the CNS from sensory receptors; mostly unipolar.

Motor Neuron

Neuron carrying impulses from the CNS to effectors; typically multipolar.

Interneuron (Association Neuron)

Neuron located entirely within the CNS that links sensory and motor pathways; 99% of all neurons.

Resting Membrane Potential

Approximately –70 mV charge difference across a resting neuron’s membrane.

Depolarization

Decrease in membrane potential, making the inside less negative and more likely to fire an impulse.

Hyperpolarization

Increase in membrane potential, making the inside more negative and less likely to fire.

Graded Potential

Short-lived, local membrane potential change whose magnitude varies with stimulus strength.

Action Potential

Brief, long-distance reversal of membrane potential (~100 mV) along an axon; the nerve impulse.

Threshold

Membrane potential (about –55 mV) that must be reached to trigger an action potential.

Absolute Refractory Period

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

Relative Refractory Period

Period when a stronger-than-usual stimulus can trigger another action potential.

Saltatory Conduction

Rapid impulse propagation in myelinated axons where the action potential jumps between nodes.

Synapse

Functional junction where information is transferred from one neuron to another or to an effector.

Presynaptic Neuron

Neuron that sends the signal toward a synapse.

Postsynaptic Neuron

Neuron that receives the signal at a synapse.

Chemical Synapse

Most common synapse type; uses neurotransmitters to bridge a synaptic cleft.

Electrical Synapse

Synapse where neurons are linked by gap junctions, allowing direct ionic current flow.

Excitatory Postsynaptic Potential (EPSP)

Depolarizing graded potential that brings the postsynaptic membrane closer to threshold.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarizing graded potential that drives the postsynaptic membrane farther from threshold.

Temporal Summation

Rapid, successive EPSPs from one presynaptic neuron add together at the postsynaptic membrane.

Spatial Summation

Simultaneous EPSPs from multiple presynaptic neurons combine at the postsynaptic membrane.

Neurotransmitter

Chemical messenger released by neurons to communicate across a synapse.

Acetylcholine (ACh)

First identified neurotransmitter; excitatory at neuromuscular junctions, degraded by AChE.

Dopamine

Catecholamine neurotransmitter involved in movement, motivation, and reward pathways.

Serotonin

Indolamine neurotransmitter derived from tryptophan; affects mood, sleep, and appetite.

GABA (Gamma-Aminobutyric Acid)

Major inhibitory neurotransmitter in the brain.

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 smooth-muscle relaxation.

Endocannabinoids

Lipid neurotransmitters that bind the same receptors as THC; influence appetite and memory.

Direct-Acting Neurotransmitter

Neurotransmitter that opens ion channels directly for rapid responses (e.g., ACh).

Indirect-Acting Neurotransmitter

Neurotransmitter that works through second messengers for slow, prolonged effects (e.g., NE).

Neuromodulator

Chemical that alters synaptic strength without directly causing EPSPs or IPSPs.

Neuronal Pool

Functional group of neurons that integrate incoming information and relay it onward.

Reflex Arc

Simple neuronal pathway responsible for automatic reflexes, containing five components.

Diverging Circuit

Neuronal circuit where one input triggers branches that spread to multiple outputs.

Converging Circuit

Circuit where many inputs funnel to a single output neuron.

Reverberating Circuit

Circuit with feedback that produces a repeating, oscillating output.

Parallel After-Discharge Circuit

Circuit where one input triggers parallel chains that reconverge, yielding bursts of output.

Growth Cone

Dynamic structure at a growing axon tip guiding it toward target cells during development.