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 central nervous system.

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.

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.

Cephalgia

Pain in the head.

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 angiography

Process of recording the blood vessels of the cerebrum.

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)

A colorless fluid produced by the brain that cushions the brain and spinal cord within the posterior (dorsal) cavity.

Cerebral thrombosis

Formation of a blood clot in a blood vessel within the skull.

Choroid plexus

Specialized structure containing ependymal cells that line blood capillaries and filter blood to produce cerebrospinal fluid 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 central nervous system.

Efferent nerves

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

Electroencephalogram

The record of electrical activity of the brain.

Electroencephalography

Process of recording the electrical activity of the brain.

Embolus

An obstruction such as a blood clot or plaque that blocks the flow of blood in an artery or vein.

Encephalitis

Inflammation of the tissues of the brain.

Encephalomalacia

Softening of the tissues of the brain.

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 central nervous system responsible for producing cerebrospinal fluid.

Epithalamus

Region of the diencephalon containing the pineal gland.

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.

Ganglionectomy

Excision of a ganglion.

Glial cell

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

Glioblastoma

A central nervous system tumor composed of developing glial tissue.

Glioma

A tumor that begins in the glial tissue.

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

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

Hemiplegia

Paralysis on one side of the body.

Hemorrhagic stroke

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

Hydrocephalus

The abnormal buildup of cerebrospinal fluid in the ventricles of the brain.

Hyperesthesia

Increased sensitivity to stimuli.

Hypothalamus

A region of the forebrain below the thalamus; has function in both the autonomic and endocrine systems and regulates 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.

Longitudinal fissure

A large separation along the midline between the two cerebral hemispheres.

Lumbar puncture

Procedure used to withdraw cerebrospinal fluid from the lower lumbar region of the vertebral column.

Medulla oblongata

A part of the brain stem responsible for control of heart rate and breathing.

Meninges

The membranes that surround the central nervous system.

Meningioma

A tumor of the meninges.

Meningitis

Inflammation of the meninges, the tough membranes that surround the central nervous system.

Meningocele

Protrusion of the meninges.

Meningomyelocele

Protrusion of the meninges and spinal cord.

Microglia

Smaller than most of the other glial cells; they ingest and digest cells or pathogens that cause disease.

Midbrain

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

Mononeuropathy

Disease affecting a single peripheral nerve.

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 sheath

Lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system; facilitates the transmission of electrical signals.

Nerves

Bundle of fibers that receives and sends messages between the body and the brain.

Neuralgia

Pain of the peripheral or cranial nerves.

Neuritis

Inflammation of a peripheral or cranial nerve.

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.

Neurologist

A doctor who has special training in diagnosing and treating disorders of the nervous system.

Neurology

A medical specialty concerned with the study of the structures, functions, and diseases of the nervous system.

Neuroma

Tumor made up of nerve cells.

Neuron

Cells that propagate information via electrochemical impulses.

Neuropathy

A nerve problem that causes pain, numbness, tingling, swelling, or muscle weakness in different parts of the body.

Neurotransmitters

Chemicals that are made by nerve cells and used to communicate with other cells, including other nerve cells and muscle cells.

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

The cell’s central organelle, which contains the cell’s DNA.

Occipital lobe

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

Olfaction

The sense of smell.

Oligodendrocyte

Glial cell type in the central nervous system that provides the myelin insulation for axons in tracts.

Paresis

Partial paralysis wherein there is still some control of the muscles.

Paresthesia

Abnormal sensation in the extremities.

Parietal lobe

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

Peripheral nervous system (PNS)

All nervous tissue that is outside of the brain and spinal cord.

Pia mater

Thin, innermost membrane of the meninges that directly covers the surface of the central nervous system.

Poliomyelitis

Acute infection by the poliovirus, especially of the motor neurons in the spinal cord and brainstem.

Polyneuritis

Inflammation of several peripheral nerves at the same time.

Polyneuropathy

Disease of multiple peripheral nerves at the same time.

Pons

The main connection between the cerebellum and the brain stem. It is responsible for regulating several crucial functions, including the cardiovascular and respiratory systems.

Process

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

Psychiatrist

A medical doctor who specializes in neuroscience and diagnoses and treats mental disorders.

Psychiatry

The medical science that deals with the origin, diagnosis, prevention, and treatment of mental disorders.

Psychologist

A specialist who can talk with patients and their families about emotional and personal matters.

Psychology

The study of how the mind works and how thoughts and feelings affect behavior.

Psychosis

A severe mental disorder in which a person loses the ability to recognize reality or relate to others.

Quadriplegia

Paralysis of all four limbs.

Radiculopathy

Disease of the nerve roots.

Response

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

Rhizotomy

Incision into a nerve root.

Satellite cell

Glial cell type in the peripheral nervous system that provides support for neurons in the ganglia.

Schwann cell

Glial cell type in the peripheral nervous system 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 behaviors.

Stimulus

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

Stroke

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

Subarachnoid space

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

Subdural hematoma

Accumulation of blood in the subdural space.

Sulcus

Groove formed by convolutions in the surface of the cerebral cortex.

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)

The division of the nervous system involved in our fight-or-flight responses. It continuously monitors body temperature and initiates appropriate motor responses.

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 cerebrospinal fluid 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.