Introduction to the Nervous System and Nervous Tissue – Vocabulary Flashcards

120 key vocabulary flashcards summarizing essential terms and concepts from Chapter 11, covering nervous system structure, neuron anatomy, neuroglia, electrophysiology, synaptic transmission, neurotransmitters, and neuronal circuits.

Nervous System

Organ system that perceives stimuli, directs movement, houses cognition, and works with the endocrine system to maintain homeostasis.

Central Nervous System (CNS)

Structural division consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

Structural division composed of cranial nerves, spinal nerves, and their branches.

Brain

CNS organ containing ~100 billion neurons; controls most integrative functions.

Spinal Cord

CNS structure with ~100 million neurons; connects brain with body below head and neck.

Cranial Nerves

Twelve pairs of nerves that originate from or travel to the brain.

Spinal Nerves

Thirty-one pairs of nerves that originate from or travel to the spinal cord.

Sensory (Afferent) Division

PNS division that carries information from sensory receptors to the CNS.

Motor (Efferent) Division

PNS division that carries commands from the CNS to effectors.

Somatic Sensory Division

PNS sensory subdivision conveying signals from skin, bones, joints, muscles, and special senses.

Visceral Sensory Division

PNS sensory subdivision conveying signals from thoracic and abdominal viscera.

Somatic Motor Division

PNS motor subdivision that innervates skeletal muscle; voluntary control.

Visceral Motor Division (Autonomic Nervous System)

PNS motor subdivision that controls cardiac muscle, smooth muscle, and glands; involuntary.

Sensory Functions

Processes that gather information about internal and external environments.

Integrative Functions

CNS activities that analyze sensory input and determine responses.

Motor Functions

Actions performed by effectors in response to integrative decisions.

Nervous Tissue

Tissue consisting mostly of neurons and neuroglia with little extracellular matrix.

Neuron (Nerve Cell)

Excitable cell that generates and transmits action potentials.

Neuroglia (Neuroglial Cell)

Supportive cell type that protects, nourishes, and insulates neurons; capable of mitosis.

Cell Body (Soma)

Metabolically active region of a neuron containing nucleus and major organelles.

Nissl Bodies

Clusters of rough ER and free ribosomes in neuron somas; sites of protein synthesis.

Dendrite

Short, branched neuronal process that receives electrical signals and conveys them to the soma.

Axon

Long neuronal process that conducts action potentials away from the soma.

Axon Hillock

Cone-shaped region where the axon originates from the soma.

Axon Collateral

Branch of an axon that enables communication with multiple targets.

Telodendria

Fine terminal branches of an axon and its collaterals.

Axon Terminal (Synaptic Knob)

Bulbous end of telodendria that releases neurotransmitter.

Axolemma

Plasma membrane of an axon.

Axoplasm

Cytoplasm within an axon.

Slow Axonal Transport

1–3 mm/day movement of cytoskeletal and other proteins away from soma.

Fast Axonal Transport

Up to 400 mm/day motor-protein-driven movement of vesicles and organelles along axon.

Retrograde Transport

Fast axonal transport toward the cell body.

Anterograde Transport

Fast axonal transport away from the cell body.

Receptive Region

Dendrites and soma region where neurons receive stimuli.

Conducting Region

Axon region that propagates action potentials.

Secretory Region

Axon terminals that release neurotransmitter to target cells.

Multipolar Neuron

Neuron with one axon and two or more dendrites; >99 % of neurons.

Bipolar Neuron

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

Pseudounipolar Neuron

Neuron with single short process that splits into peripheral and central axons; sensory for touch, pain.

Sensory (Afferent) Neuron

Neuron that conveys information toward the CNS.

Interneuron (Association Neuron)

Multipolar neuron that relays signals within the CNS.

Motor (Efferent) Neuron

Neuron that carries commands from CNS to muscles or glands.

Nucleus (Neuronal)

Cluster of neuron cell bodies in the CNS.

Ganglion

Cluster of neuron cell bodies in the PNS.

Tract

Bundle of axons in the CNS.

Nerve

Bundle of axons in the PNS.

Astrocyte

Star-shaped CNS glial cell that anchors neurons, regulates ECF, forms blood–brain barrier, and repairs tissue.

Oligodendrocyte

CNS glial cell whose processes form myelin sheaths around multiple axons.

Microglia

Small phagocytic CNS glia activated by injury; ingest debris and pathogens.

Ependymal Cell

Ciliated CNS glial cell that lines ventricles and circulates cerebrospinal fluid.

Schwann Cell (Neurolemmocyte)

PNS glial cell that myelinates and repairs peripheral axons.

Satellite Cell

Flat PNS glial cell that surrounds neuron somas and regulates their environment.

Myelin Sheath

Repeated layers of glial plasma membrane that insulate axons and speed conduction.

Internode

Segment of axon covered by myelin.

Node of Ranvier

Gap between myelin internodes where voltage-gated channels cluster.

Neurolemma

Outer cytoplasmic layer of a myelinating Schwann cell.

White Matter

Myelinated regions of the CNS appearing lighter in color.

Gray Matter

Unmyelinated CNS regions containing neuronal cell bodies.

Regeneration Tube

Schwann-cell-basal-lamina structure guiding regrowth of a damaged PNS axon.

Resting Membrane Potential

~−70 mV charge difference across a neuron’s membrane at rest.

Leak Channel

Ion channel that is always open and sets resting permeability.

Ligand-Gated Channel

Channel that opens when a chemical messenger binds.

Voltage-Gated Channel

Channel that opens or closes in response to membrane potential changes.

Mechanically Gated Channel

Channel that opens in response to stretch, pressure, or vibration.

Sodium-Potassium Pump

ATPase that moves 3 Na⁺ out and 2 K⁺ into a cell to maintain gradients.

Depolarization

Membrane potential becomes less negative (toward zero).

Repolarization

Return of membrane potential to resting value after depolarization.

Hyperpolarization

Membrane potential becomes more negative than resting level.

Local (Graded) Potential

Small, reversible, decremental change in membrane potential over short distance.

Action Potential

All-or-none, rapid depolarization–repolarization that propagates along axon.

Trigger Zone

Initial segment of axon where action potentials are generated.

Absolute Refractory Period

Time during which no stimulus can initiate another action potential.

Relative Refractory Period

Period when only a stronger-than-normal stimulus can evoke an action potential.

Continuous Conduction

Propagation along unmyelinated axons; each segment depolarizes sequentially.

Saltatory Conduction

Fast propagation in myelinated axons where impulses jump between nodes.

Type A Fibers

Largest, myelinated axons with fastest conduction; serve somatic motor and some sensory pathways.

Type B Fibers

Intermediate, mostly myelinated axons with moderate speed; visceral sensory and autonomic efferent.

Type C Fibers

Small, unmyelinated axons with slowest speed; transmit pain, temperature, some autonomic signals.

Synapse

Junction where a neuron communicates with another cell.

Presynaptic Neuron

Neuron that releases neurotransmitter at a synapse.

Postsynaptic Neuron

Cell that receives neurotransmitter signal at a synapse.

Electrical Synapse

Gap-junction-coupled synapse allowing rapid, bidirectional ionic current flow.

Chemical Synapse

Synapse that converts electrical signal to chemical neurotransmitter and back.

Synaptic Vesicle

Membrane sac in axon terminal containing neurotransmitter molecules.

Neurotransmitter

Chemical messenger released by neurons to transmit signals across synapses.

Synaptic Cleft

20–50 nm space between presynaptic and postsynaptic membranes at a chemical synapse.

Excitatory Postsynaptic Potential (EPSP)

Small depolarization moving the postsynaptic membrane toward threshold.

Inhibitory Postsynaptic Potential (IPSP)

Small hyperpolarization moving the postsynaptic membrane away from threshold.

Temporal Summation

Addition of postsynaptic potentials generated in rapid succession at one synapse.

Spatial Summation

Addition of simultaneous postsynaptic potentials from multiple synapses.

Ionotropic Receptor

Ligand-gated ion channel that produces fast, short-lived postsynaptic effects.

Metabotropic Receptor

G-protein-coupled receptor that triggers second-messenger cascades; slower, longer-lasting effects.

Acetylcholine (ACh)

Neurotransmitter at neuromuscular junctions, many CNS synapses, and the ANS; broken down by AChE.

Biogenic Amines (Monoamines)

Family of neurotransmitters derived from amino acids, including catecholamines, serotonin, and histamine.

Norepinephrine

Catecholamine involved in ANS functions and CNS regulation of attention and arousal.

Epinephrine

Catecholamine acting mainly as hormone; also CNS/ANS neurotransmitter similar to norepinephrine.

Dopamine

CNS catecholamine important for movement, motivation, and reward pathways.

Serotonin

Tryptophan-derived neurotransmitter involved in mood, appetite, and sleep regulation.

Histamine

Neurotransmitter regulating arousal and attention in CNS; mediator of allergic responses peripherally.

Glutamate

Most abundant excitatory neurotransmitter in the brain.