Vocabulary & Check Your Knowledge

Nervous System Vocabulary

Afferent nerves
Nerves that carry sensory signals (nerve impulses) toward the CNS from the periphery.

Aphasia
Loss of language function.

Arachnoid mater
Middle layer of the meninges named for the spider-web–like trabeculae that extend between it and the pia mater.

Astrocyte
Glial cell type of the CNS that provides support for neurons and maintains the blood-brain barrier.

Autonomic nervous system (ANS)
Functional division of the nervous system that is responsible for homeostatic reflexes that coordinate control of cardiac and smooth muscle, as well as glandular tissue.

Axon
Single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell.

Axon hillock
Tapering of the neuron cell body that gives rise to the axon.

Axon segment
Single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal).

Axon terminal
End of the axon, where there are usually several branches extending toward the target cell.

Axoplasm
Cytoplasm of an axon, which is different in composition than the cytoplasm of the neuronal cell body.

Babinski Sign
Dorsiflexion of the foot with extension and splaying of the toes in response to the plantar reflex, normally suppressed by corticospinal input.

Bipolar
Shape of a neuron with two processes extending from the neuron cell body—the axon and one dendrite.

Blood-brain Barrier (BBB)
Physiological barrier between the circulatory system and the central nervous system that establishes a privileged blood supply, restricting the flow of substances into the CNS.

Brain
The large organ of the central nervous system composed of white and gray matter, contained within the cranium and continuous with the spinal cord.

Brain Stem
Region of the adult brain that includes the midbrain, pons, and medulla oblongata and develops from the mesencephalon, metencephalon, and myelencephalon of the embryonic brain.

Broca’s Area
Region of the frontal lobe associated with the motor commands necessary for speech production and located only in the cerebral hemisphere responsible for language production, which is the left side in approximately 95 percent of the population

Brodmann’s Areas
Mapping of regions of the cerebral cortex based on microscopic anatomy that relates specific areas to functional differences, as described by Brodmann in the early 1900s.

Cauda Equina
Bundle of spinal nerve roots that descend from the lower spinal cord below the first lumbar vertebra and lie within the vertebral cavity; has the appearance of a horse’s tail.

Caudate
Nucleus deep in the cerebrum that is part of the basal nuclei; along with the putamen, it is part of the striatum.

Central nervous system (CNS)
Anatomical division of the nervous system located within the cranial and vertebral cavities, namely the brain and spinal cord.

Central Sulcus

Surface landmark of the cerebral cortex that marks the boundary between the frontal and parietal lobes.

Cerebellum
Region of the adult brain connected primarily to the pons that developed from the metencephalon (along with the pons) and is largely responsible for comparing information from the cerebrum with sensory feedback from the periphery through the spinal cord.

Cerebral Cortex
Outer gray matter covering the forebrain, marked by wrinkles and folds known as gyri and sulci.

Cerebrum
Region of the adult brain that develops from the telencephalon and is responsible for higher neurological functions such as memory, emotion, and consciousness.

Cerebral Hemisphere

One half of the bilaterally symmetrical cerebrum.

Cerebrospinal Fluid (CSF)

Circulatory medium within the CNS that is produced by ependymal cells in the choroid plexus filtering the blood.

Choroid Plexus
Specialized structure containing ependymal cells that line blood capillaries and filter blood to produce CSF in the four ventricles of the brain.

Corpus callosum
Large white matter structure that connects the right and left cerebral hemispheres.

Dendrite
One of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells.

Descending tract
Central nervous system fibers carrying motor commands from the brain to the spinal cord or periphery.

Diencephalon
Region of the adult brain that retains its name from embryonic development and includes the thalamus and hypothalamus.

Direct pathway
Connections within the basal nuclei from the striatum to the globus pallidus internal segment and substantia nigra pars reticulata that disinhibit the thalamus to increase cortical control of movement.

Dorsal (posterior) nerve root
Axons entering the posterior horn of the spinal cord.

Dura mater
Tough, fibrous, outer layer of the meninges that is attached to the inner surface of the cranium and vertebral column and surrounds the entire CNS.

Efferent nerves
Nerve tissue that carries impulses away from the CNS towards the peripheral that result in motor response (movement).

Embolus
Obstruction in a blood vessel such as a blood clot, fatty mass, air bubble, or other foreign matter that interrupts the flow of blood to an organ or some part of the body.

Enteric nervous system (ENS)
Neural tissue associated with the digestive system that is responsible for nervous control through autonomic connections.

Ependymal cell
Glial cell type in the CNS responsible for producing cerebrospinal fluid.

Epithalamus
Region of the diencephalon containing the pineal gland.

Fissures
A groove, natural division or elongated cleft, furrow or tear; naturally occurring in the brain, they are also known as sulcus/sulci.

Foramen magnum
Large opening in the occipital bone of the skull through which the spinal cord emerges and the vertebral arteries enter the cranium.

Frontal lobe
Region of the cerebral cortex directly beneath the frontal bone of the cranium.

Ganglion
Localized collection of neuron cell bodies in the peripheral nervous system.

Glial cell
One of the various types of neural tissue cells responsible for maintenance of the tissue, and largely responsible for supporting neurons.

Gray matter
Regions of the nervous system containing cell bodies of neurons with few or no myelinated axons; actually may be more pink or tan in color, but called gray in contrast to white matter.

Gyrus/gyri
Ridge formed by convolutions on the surface of the cerebrum or cerebellum.

Hemorrhagic stroke
Disruption of blood flow to the brain caused by bleeding within the cranial vault.

Hydrocephalus
An abnormal buildup of cerebrospinal fluid (CSF) in the ventricles of the brain.

Hypothalamus
Major region of the diencephalon that is responsible for coordinating autonomic and endocrine control of homeostasis.

Ischemic stroke
Disruption of blood flow to the brain because blood cannot flow through blood vessels as a result of a blockage or narrowing of the vessel.

Integration

Nervous system function that combines sensory perceptions and higher cognitive functions (memories, learning, emotion, etc.) to produce a response.

Initial segment
First part of the axon as it emerges from the axon hillock, where the electrical signals known as action potentials are generated.

Lumbar puncture
Procedure used to withdraw CSF from the lower lumbar region of the vertebral column that avoids the risk of damaging CNS tissue because the spinal cord ends at the upper lumbar vertebrae.

Medulla oblongata
The continuation of the spinal cord within the skull, forming the lowest part of the brainstem, contains the control centers for heart and lung nerve function.

Meninges
Protective outer coverings of the CNS composed of connective tissue.

Microglia
Glial cell type in the CNS that serves as the resident component of the immune system.

Midbrain
A portion of the brainstem, positioned above the pons, also called mesencephalon, assist in motor reflexes associated with visual and auditory stimuli.

Motor nerves
Peripheral, efferent, myelinated nerve tissue that stimulates muscle contraction.

Multipolar
Shape of a neuron that has multiple processes—the axon and two or more dendrites.

Myelin
Lipid-rich insulating substance surrounding the axons of many neurons, allowing for faster transmission of electrical signals.

Myelin sheath
Lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates the transmission of electrical signals.

Nerve
Cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the central nervous system.

Neuron
Neural tissue cell that is primarily responsible for generating and propagating electrical signals into, within, and out of the nervous system.

Neuroglia
Supportive tissue of the nervous system, including the network of branched cells in the central nervous system (astrocytes, microglia, and oligodendrocytes) and the supporting cells of the peripheral nervous system (Schwann cells and satellite cells), also called glia.

Neurotransmitter
Chemical that is released from a nerve cell, transmits an impulse from a nerve cell to another nerve, muscle, organ, or other tissue.

Node of Ranvier
Gap between two myelinated regions of an axon, allowing for strengthening of the electrical signal as it propagates down the axon.

Nucleus
In the nervous system, a localized collection of neuron cell bodies that are functionally related; a “center” of neural function.

Occipital lobe
Region of the cerebral cortex directly beneath the occipital bone of the cranium.

Olfaction
Special sense responsible for smell, which has a unique, direct connection to the cerebrum.

Oligodendrocyte
Glial cell type in the CNS that provides the myelin insulation for axons in tracts.

Paresis
Partial loss of, or impaired, voluntary muscle control.

Parietal lobe
Region of the cerebral cortex directly beneath the parietal bone of the cranium.

Peripheral nervous system (PNS)
Anatomical division of the nervous system that is largely outside the cranial and vertebral cavities, namely all parts except the brain and spinal cord.

Pia mater
Thin, innermost membrane of the meninges that directly covers the surface of the CNS.

Pons
Latin word meaning bridge, essential part of the brain located above the medulla, action in regulation and controls of vital functions primarily sleep, respiration, swallowing, bladder control, hearing, balance (equilibrium), taste, ocular movement, facial expression and sensation.

Process
In cells, an extension of a cell body; in the case of neurons, this includes the axon and dendrites.

Response
Nervous system function that causes a target tissue (muscle or gland) to produce an event as a consequence to stimuli.

Satellite cell
Glial cell type in the PNS that provides support for neurons in the ganglia.

Schwann cell
Glial cell type in the PNS that provides the myelin insulation for axons in nerves.

Sensation
Nervous system function that receives information from the environment and translates it into the electrical signals of nervous tissue.

Soma
In neurons, that portion of the cell that contains the nucleus; the cell body, as opposed to the cell processes (axons and dendrites).

Somatic nervous system (SNS)
Functional division of the nervous system that is concerned with conscious perception, voluntary movement, and skeletal muscle reflexes.

Spinal cord
Organ of the central nervous system found within the vertebral cavity and connected with the periphery through spinal nerves; mediates reflex behaviours.

Stimulus
An event in the external or internal environment that registers as activity in a sensory neuron.

Stroke
(also, cerebrovascular accident (CVA)) loss of neurological function caused by an interruption of blood flow to a region of the central nervous system.

Subarachnoid space
Space between the arachnoid mater and pia mater that contains CSF and the fibrous connections of the arachnoid trabeculae.

Sulcus/sulci
Groove formed by convolutions in the surface of the cerebral cortex; see fissure.

Synapse
Narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell.

Synaptic end bulb
Swelling at the end of an axon where neurotransmitter molecules are released onto a target cell across a synapse.

Sympathetic nervous system (SNS)
Part of the nervous system that serves to accelerate heart rate, constrict blood vessels and raise blood pressure in response to stress.

Temporal lobe
Region of the cerebral cortex directly beneath the temporal bone of the cranium.

Thalamus
Major region of the diencephalon that is responsible for relaying information between the cerebrum and the hindbrain, spinal cord, and periphery.

Tract
Bundle of axons in the central nervous system having the same function and point of origin.

Transient ischemic attack (TIA)
Temporary disruption of blood flow to the brain in which symptoms occur rapidly but last only a short time.

Unipolar
Shape of a neuron which has only one process that includes both the axon and dendrite.

Ventricle
Central cavity within the brain where CSF is produced and circulates.

Wernicke’s area
Region at the posterior end of the lateral sulcus in which speech comprehension is localized.

White matter

Regions of the nervous system containing mostly myelinated axons, making the tissue appear white because of the high lipid content of myelin.

Attribution

Except where otherwise noted, this chapter is adapted from Nervous System” in Building a Medical Terminology Foundation by Kimberlee Carter and Marie Rutherford, licensed under CC BY 4.0. / A derivative of Betts et al., which can be accessed for free from Anatomy and Physiology (OpenStax). Adaptations: dividing Nervous System chapter content into sub-chapters.