Introduction to the Nervous System – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering key terms and definitions from Chapter 12: Introduction to the Nervous System.

Nervous System

Body system that senses internal/external changes and coordinates responses to maintain homeostasis.

Endocrine System

Glandular system that works with the nervous system to regulate long-term homeostasis via hormones.

Neuron

Electrically excitable cell that converts stimuli into nerve impulses; the basic communicative unit of the nervous system.

Neuroglia (Glia)

Supporting cells of nervous tissue that nourish, protect, and insulate neurons; can divide but do not conduct impulses.

Central Nervous System (CNS)

Brain and spinal cord; integrates sensory input, issues motor commands, and houses thoughts and memories.

Peripheral Nervous System (PNS)

All nervous tissue outside the CNS, including cranial nerves, spinal nerves, ganglia, enteric plexuses, and sensory receptors.

Somatic Nervous System (SNS)

PNS subdivision with sensory neurons from skin/special senses and voluntary motor neurons to skeletal muscle.

Autonomic Nervous System (ANS)

PNS subdivision with sensory input from viscera and involuntary motor output to smooth muscle, cardiac muscle, and glands.

Enteric Nervous System (ENS)

Intrinsic nerve network of the GI tract that monitors and controls digestive functions, mostly independent of CNS/ANS.

Sensory Function

Detection of internal and external stimuli and transmission of that information to the CNS.

Integrative Function

Processing and interpretation of sensory input within the CNS to determine response.

Motor Function

Activation of effectors (muscles or glands) to carry out responses commanded by the CNS.

Dendrite

Short, branched neuronal process that receives incoming signals and generates graded potentials.

Cell Body (Soma)

Neuron region containing nucleus, organelles, Nissl bodies, and most metabolic machinery.

Axon

Long neuronal process that propagates action potentials from the cell body to another neuron or effector.

Axon Hillock

Cone-shaped junction between cell body and axon; typical trigger zone for action potentials.

Axon Collateral

Side branch of an axon that can innervate additional targets.

Axon Terminal

Distal end of an axon that forms synapses; often enlarged into synaptic end bulbs.

Synaptic End Bulb

Swollen axon terminal containing synaptic vesicles with neurotransmitter.

Nissl Bodies

Clusters of rough ER in neuron cell bodies dedicated to protein synthesis.

Neurofibrils

Cytoskeletal bundles of intermediate filaments and microtubules that move materials within neurons.

Multipolar Neuron

Neuron with several dendrites and one axon; most common type in brain and spinal cord; often motor.

Bipolar Neuron

Neuron with one dendrite and one axon; found in retina, inner ear, and olfactory epithelium.

Unipolar Neuron

Sensory neuron whose single process divides into two axon-like branches; cell bodies in ganglia.

Sensory (Afferent) Neuron

Carries sensory information toward the CNS.

Motor (Efferent) Neuron

Conveys commands from the CNS to effectors.

Interneuron

CNS neuron that processes information and connects sensory and motor pathways.

Schwann Cell

PNS glial cell that forms myelin around one axon and aids in axon regeneration.

Satellite Cell

Flat PNS glial cell that surrounds neuron cell bodies in ganglia and regulates their environment.

Myelin Sheath

Multilayered lipid-protein covering around axons that insulates and speeds impulse conduction.

Neurolemma

Outer cytoplasmic layer of a Schwann cell that facilitates axon regeneration in the PNS.

Node of Ranvier

Gap between myelin segments where voltage-gated channels cluster and saltatory conduction occurs.

Oligodendrocyte

CNS glial cell that forms and maintains myelin around multiple axons.

Astrocyte

Star-shaped CNS glial cell that provides nutrients, regulates ion balance, and helps form the blood-brain barrier.

Microglia

Small CNS phagocytic glial cells that remove debris and microbes.

Ependymal Cell

Ciliated CNS glial cell lining ventricles and spinal canal; produces and circulates cerebrospinal fluid.

White Matter

CNS regions rich in myelinated axons; deep in brain, superficial in spinal cord.

Gray Matter

CNS regions with neuron cell bodies, unmyelinated axons, and glia; superficial in brain cortex, deep in spinal cord.

Graded Potential

Small, variable change in membrane potential used for short-distance communication.

Action Potential

All-or-none electrical impulse that travels long distances along axons.

Resting Membrane Potential

Stable voltage difference (≈-70 mV) across a neuron's membrane due to ion distribution and pump activity.

Leak Channel

Ion channel that randomly opens and closes, allowing passive ion movement.

Ligand-Gated Channel

Membrane channel that opens or closes when a specific chemical binds to its receptor.

Mechanically-Gated Channel

Ion channel that responds to physical deformation of the membrane.

Voltage-Gated Channel

Channel that opens in response to changes in membrane potential; crucial for action potentials.

Depolarization

Membrane potential becomes less negative (moves toward zero or positive).

Hyperpolarization

Membrane potential becomes more negative than resting level.

Threshold

Critical depolarization level (about –55 mV) that triggers an action potential.

Absolute Refractory Period

Time during which a second action potential cannot be generated regardless of stimulus strength.

Relative Refractory Period

Interval when a stronger-than-normal stimulus can elicit another action potential.

Continuous Conduction

Step-by-step propagation of an impulse along an unmyelinated axon.

Saltatory Conduction

Rapid impulse propagation in myelinated axons where action potentials leap between nodes of Ranvier.

Excitatory Postsynaptic Potential (EPSP)

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

Inhibitory Postsynaptic Potential (IPSP)

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

Summation

Process by which graded potentials combine to influence action potential generation.

Temporal Summation

Summation of potentials from a single presynaptic neuron firing at high frequency.

Spatial Summation

Summation of simultaneous inputs from multiple presynaptic neurons.

Synapse

Specialized junction where a neuron communicates with another cell.

Presynaptic Neuron

Neuron that sends the signal toward a synapse.

Postsynaptic Neuron

Neuron that receives the signal at a synapse.

Axodendritic Synapse

Synapse between an axon terminal and a dendrite.

Axosomatic Synapse

Synapse between an axon terminal and a neuron’s cell body.

Axoaxonic Synapse

Synapse between one axon and the axon hillock of another neuron.

Neurotransmitter

Chemical messenger released by neurons to transmit signals across synapses.

Acetylcholinesterase

Synaptic enzyme that degrades acetylcholine, terminating its action.

Plasticity

Ability of the nervous system to change its structure and function in response to experience.

Chromatolysis

Breakdown of Nissl bodies in the neuron cell body after axonal injury.

Wallerian Degeneration

Degeneration of the distal axon segment and myelin after injury.

Regeneration Tube

Schwann-cell-formed guide that directs regrowth of a damaged PNS axon.

Multiple Sclerosis (MS)

Autoimmune demyelinating disease of the CNS characterized by plaques, inflammation, and neural conduction loss.