Nervous System (Chapter 10)

Vocabulary flashcards for Lesson 10.1–10.3 covering structure, function, cells, and disorders of the nervous system.

Nervous system

Network of organs and cells coordinating body activities through electrical impulses and chemical signals.

Central nervous system (CNS)

Brain and spinal cord—the main integrating centers of the nervous system.

Peripheral nervous system (PNS)

All nerves outside the CNS.

Autonomic nervous system (ANS)

Involuntary motor nerves regulating internal organs and glands.

Neuron

Nerve cell that transmits electrical impulses; composed of cell body, dendrites, and an axon.

Cell body

Main part of a neuron containing the nucleus and organelles.

Dendrite

Branching projections that conduct impulses toward the cell body.

Axon

Elongated projection that conducts impulses away from the cell body.

Myelin sheath

Insulating layer around axons that speeds conduction; formed by Schwann cells in the PNS and oligodendrocytes in the CNS.

Node of Ranvier

Gaps between myelin segments where ion exchange occurs to propagate the impulse.

Schwann cell

Glial cell that forms the myelin sheath around PNS axons.

Neurilemma

Outer membrane of a Schwann cell around a myelinated PNS axon.

Glia (neuroglia)

Support cells that structurally and functionally support nervous tissue.

Astrocyte

Star-shaped glial cell that anchors small blood vessels to neurons.

Microglia

Small glial cells that move in inflamed brain tissue and perform phagocytosis.

Oligodendrocyte

Glial cell that forms myelin sheaths on CNS axons.

Glioma

Glial tumor; most nervous-system tumors are gliomas.

Multiple sclerosis (MS)

Demyelinating disease of CNS; myelin loss impairs conduction.

Demyelination

Loss of myelin on nerve fibers.

Sensory (afferent) neuron

Conveys impulses to spinal cord and brain.

Motor (efferent) neuron

Conveys impulses from CNS to muscles and glands.

Interneuron

Connects sensory to motor neurons; located in CNS.

Nerve

Bundle of peripheral axons within a connective tissue sheath.

Tract

Bundle of central axons within the CNS.

White matter

Brain or cord tissue primarily composed of myelinated axons.

Gray matter

Brain or cord tissue composed mainly of neuron cell bodies and unmyelinated fibers.

Endoneurium

Connective tissue surrounding each individual nerve fiber.

Perineurium

Connective tissue surrounding a fascicle (group) of nerve fibers.

Epineurium

Connective tissue surrounding the entire nerve.

Dorsal root ganglion

Cluster of sensory neuron cell bodies in the dorsal root.

Reflex arc

Nerve pathway that produces a reflex; simplest arcs are two- or three-neuron circuits.

Two-neuron reflex arc

Sensory neuron synapses with motor neuron in the spinal cord.

Three-neuron reflex arc

Sensory neuron synapses with interneuron in the spinal cord; interneuron synapses with a motor neuron.

Synapse

Junction where impulses are transmitted from one neuron to another; includes synaptic knob, cleft, and postsynaptic membrane.

Neurotransmitter

Chemical messenger released at a synapse that binds to receptors on the postsynaptic membrane to stimulate or inhibit a response.

Acetylcholine

Cholinergic neurotransmitter released by parasympathetic and some sympathetic neurons.

Norepinephrine (noradrenaline)

Adrenergic neurotransmitter released by sympathetic postganglionic neurons.

Dopamine

Neurotransmitter involved in movement control; low levels linked to Parkinson disease.

Serotonin

Neurotransmitter involved in mood regulation.

Endorphins

Endogenous opioid peptides that modulate pain.

Enkephalins

Endogenous opioids that modulate pain.

Nitric oxide (NO)

Gaseous neurotransmitter involved in signaling.

Parkinson disease

Neurodegenerative disease characterized by tremor, rigidity, and bradykinesia due to dopamine loss.

Neurofibromatosis

Condition with numerous benign tumors on nerves (nerve sheath tumors).

Nerve impulse

Self-propagating electrical disturbance along a neuron membrane; the nerve impulse is the action potential.

Action potential

Nerve impulse; a self-propagating wave of depolarization along the membrane.

Depolarization

Opening of Na+ channels; inside becomes more positive.

Repolarization

Return to resting membrane potential after depolarization.

Sodium ions (Na+)

Positively charged ions outside the resting neuron; influx causes depolarization.

Saltatory conduction

Propagation of action potentials by jumping between nodes of Ranvier in myelinated fibers.

Unmyelinated nerve fiber

Nerve fiber lacking myelin; conducts impulses continuously.

Myelinated nerve fiber

Nerve fiber covered with myelin; conducts via saltatory conduction.

Synaptic knob

End of presynaptic axon containing vesicles with neurotransmitters.

Synaptic cleft

Gap across which neurotransmitters diffuse to the postsynaptic membrane.

Postsynaptic receptor

Membrane receptor on the postsynaptic neuron that binds neurotransmitters.

Cerebrospinal fluid (CSF)

Fluid surrounding brain and spinal cord; cushions and nourishes CNS tissue.

Subarachnoid space

Space between arachnoid and pia mater containing CSF.

Cerebral ventricles

Ventricles in the brain where CSF is produced and circulates.

Hydrocephalus

Enlarged ventricles due to blocked CSF flow or impaired absorption.

Brainstem

Lower part of the brain that provides two-way conduction and reflex centers.

Medulla oblongata

Lower part of the brainstem containing autonomic reflex centers.

Pons

Brainstem part involved in conduction and reflexes; houses several autonomic centers.

Midbrain

Upper part of the brainstem containing pathways and reflex centers.

Cerebellum

Second largest brain region; coordinates movement and balance; may assist other brain regions.

Hypothalamus

Major center for controlling the ANS; regulates pituitary function, appetite, wakefulness.

Thalamus

Relay center for sensory impulses to cortex; contributes to emotional aspects of sensory experience.

Cerebrum

Largest part of the brain; site of mental processes, memory, sensations, and voluntary movement.

Cerebral cortex

Outer gray matter layer of the cerebrum; consists of lobes and neuron cell bodies.

Spinal cord

CNS conduit within the vertebral column; center for spinal reflexes and two-way conduction.