Anatomy of the Central Nervous System Glossary of Terms

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Abdominal: Relating to the abdomen, the belly, that part of the body that contains all of the structures between the chest and the pelvis. The abdomen is separated anatomically from the chest by the diaphragm, the powerful muscle spanning the body cavity below the lungs.
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Afferent: Carrying toward. A vein is an afferent vessel since it carries blood toward from the heart. An afferent nerve carries impulses toward the central nervous system. The opposite of afferent is efferent.

Amygdala: 1. The amygdaloid nucleus in the brain. 2. The tonsils. These structures were so named because they appeared to be shaped like an almond. From the Greek amydale (almond) + the Greek eidos (like).

Anatomy: The study of form. Gross anatomy involves structures that can be seen with the naked eye. It is as opposed to microscopic anatomy (or histology) which involves structures seen under the microscope. Traditionally, both gross and microscopic anatomy have been studied in the first year of medical school in the U.S. The most celebrated textbook of anatomy in the English-speaking world is Gray's Anatomy, still a useful reference book. The word "anatomy" comes from the Greek ana- meaning up or through + tome meaning a cutting. Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, cutting it up. The abbreviation for anatomy is anat.

Anterior: The front, as opposed to the posterior. The anterior surface of the heart is toward the breast bone (the sternum).
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Arms: An appendage in anatomy and in clinical trials. See: Arm.

Auditory cortex: The part of the brain that is concerned with hearing. The auditory cortex is the temporal lobe, which the lower lobe of the cerebral hemisphere just forward of the occipital lobe.

Basal ganglia: A region consisting of 3 clusters of neurons (called the caudate nucleus, putamen, and the globus pallidus) located at the base of the brain that are responsible for involuntary movements such as tremors, athetosis, and chorea. The basal ganglia are abnormal in a number of important neurologic conditions including Parkinson disease and Huntington disease. The term "basal ganglia" refers to the fact that this region is in the "basement" of the brain.

Blood pressure: The blood pressure is the pressure of the blood within the arteries. It is produced primarily by the contraction of the heart muscle. It's measurement is recorded by two numbers. The first (systolic pressure) is measured after the heart contracts and is highest. The second (diastolic pressure) is measured before the heart contracts and lowest. A blood pressure cuff is used to measure the pressure. Elevation of blood pressure is called "hypertension".

Brain: That part of the central nervous system that is located within the cranium (skull). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."

Brainstem: The lowest part of the brain which merges with the spinal cord and provides the major route by which the upper realms of the brain send information to, and receives information from, the spinal cord and peripheral nerves. The brainstem consists of the medulla oblongata, midbrain, and pons. All but two of the 12 cranial nerves originate in the brainstem. The brainstem influences basic processes such as alertness, breathing, blood pressure, and heart rate.

Bridge: A set of one or more false teeth supported by a metal framework, used to replace one or more missing teeth.
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Cartilage: Firm, rubbery tissue that cushions bones at joints. A more flexible kind of cartilage connects muscles with bones and makes up other parts of the body, such as the larynx and the outside parts of the ears.

Cauda equina: A bundle of spinal nerve roots that arise from the bottom end of the spinal cord. The cauda equina comprises the roots of all the spinal nerve roots below the level of the first lumbar (L1) vertebra, namely the sacral and coccygeal nerves. So named because it resembles the tail (Latin, cauda) of a horse (Latin, equus). See also Cauda equina syndrome.

Caudate nucleus: In each hemisphere of the brain, the most medial of the four basal ganglia, partly responsible for body movement and coordination. So named because it looks anatomically tail-like (the Latin cauda, tail).

Cavities: Holes in the two outer layers of a tooth called the enamel and the dentin. The enamel is the outermost white hard surface and the dentin is the yellow layer just beneath enamel. Both layers serve to protect the inner living tooth tissue called the pulp, where blood vessels and nerves reside. Small cavities may not cause pain, and may be unnoticed by the patient. Larger cavities can collect food, and the inner pulp of the affected tooth can become irritated by bacterial toxins, foods that are cold, hot, sour, or sweet - causing toothache. Also referred to as caries.

Cell: The basic structural and functional unit in people and all living things. Each cell is a small container of chemicals and water wrapped in a membrane.
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Cerebellum: The portion of the brain in the back of the head between the cerebrum and the brain stem. The cerebellum controls balance for walking and standing and other complex motor functions.

Cerebral: Pertaining to the brain, the cerebrum or the intellect.
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Cerebral cortex: A thin mantle of gray matter about the size of a formal dinner napkin covering the surface of each cerebral hemisphere. The cerebral cortex is crumpled and folded, forming numerous convolutions (gyri) and crevices (sulci). It is made up of six layers of nerve cells and the nerve pathways that connect them. The cerebral cortex is responsible for the processes of thought, perception and memory and serves as the seat of advanced motor function, social abilities, language, and problem solving.
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Cerebral hemispheres: The two halves of the cerebrum, the largest part of the brain.

Cerebrospinal fluid: CSF. A watery fluid, continuously produced and absorbed, which flows in the ventricles (cavities) within the brain and around the surface of the brain and spinal cord.
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Cerebrum: The largest part of the brain. It is divided into two hemispheres, or halves.
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Cervical: Having to do with any kind of neck including the neck on which the head is perched and the neck of the uterus. The word "cervix" in Latin means "neck". That is why cervical vertebrae and cervical cancer involve quite disparate parts of the anatomy joined only by the meaning of the word "cervix".

Chest: The area of the body located between the neck and the abdomen. The chest contains the lungs, the heart and part of the aorta. The walls of the chest are supported by the dorsal vertebrae, the ribs, and the sternum.
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Coccygeal: Referring to the coccyx, the small tail-like bone at the bottom of the spine, that is made up of 3-5 (average of 4) rudimentary vertebrae. There is a coccygeal nerve that originates in the spinal cord and emerges at the level of the coccyx.

Corpus: The body of the uterus (womb).

Cortex: The outer portion of an organ.
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Cortical: Having to do with the cortex, the outer portion of an organ.
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Cranial: 1. Pertaining to the cranium or skull. 2. Toward the head. As opposed to caudad. The eye is cranial to the jaw. For a more complete listing of terms used in medicine for spatial orientation, please see the entry to "Anatomic Orientation Terms".

Cranial nerves: Nerves that emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column. Cranial nerves come directly from the brain through the skull.
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Dura: The outermost, toughest, and most fibrous of the three membranes (meninges) covering the brain and the spinal cord. Dura is short for dura mater (from the Latin for hard mother). Also called the pachymeninx (singular) or pachymeniges (plural).
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Efferent: Carrying away. An artery is an efferent vessel carrying blood away from the heart. An efferent nerve carries impulses away from the central nervous system. The opposite of efferent is afferent.

Endocrine: Pertaining to hormones and the glands that make and secrete them into the bloodstream through which they travel to affect distant organs. The endocrine sites include the hypothalamus, pituitary gland, pineal gland, thyroid, parathyroids, heart (which makes atrial-natriuretic peptide), the stomach and intestines, islets of Langerhans in the pancreas, the adrenal glands, the kidney (which makes renin, erythropoietin, and calcitriol), fat cells (which make leptin). the testes, the ovarian follicle (estrogens) and the corpus luteum in the ovary). Endocrine is as opposed to exocrine. (The exocrine glands include the salivary glands, sweat glands and glands within the gastrointestinal tract.)
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Facial muscle: One of the 43 muscles in the human face. The facial muscles convey basic human emotions such as anger, sadness, fear, surprise, disgust, contempt and happiness by very clear facial signals.

Fornix: In anatomy, a vaultlike or arched structure.
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Frontal: In anatomy, pertaining to the forehead. As, for example, the frontal bone, frontal sinus, and frontal nerve. From the Latin "frons" meaning the forehead or brow.

Frontal lobe: The part of each hemisphere of the brain located behind the forehead that serves to regulate and mediate the higher intellectual functions. The frontal lobes have intricate connections to other areas of the brain. In the frontal lobes, we meld emotions, cognition, error detection, volition, a sense of self, and more to create our social brain.

Genital: Pertaining to the external and internal organs of reproduction. (Not to be confused with genetic.)

Gland: 1. A group of cells that secrete a substance for use in the body. For example, the thyroid gland. 2. A group of cells that removes materials from the circulation. For example, a lymph gland.

Globus: A word straight from the Latin, meaning (not unexpectedly) a globe or sphere. The word "globus" is used in a number of different contexts in medicine.
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Globus pallidus: A pale-appearing spherical area in the brain. The globus pallidus is part of what is called the lentiform nucleus which, in turn, is part of the striate body, a component of the basal ganglia, large masses of gray matter at the base of the cerebral hemispheres of the brain.
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Gray matter: The cortex of the brain which contains nerve cell bodies. The gray matter is in contrast to the white matter, the part of the brain that contains myelinated nerve fibers. The gray matter is so named because it in fact appears gray. The white matter is white because that is the color of myelin, the insulation covering the nerve fibers. In "The Mysterious Affair at Styles" (1920), Agatha Christie first quoted the fictional Belgian detective Hercule Poirot in regard to his gray matter: "'This affair must be unravelled from within.' He tapped his forehead. 'These little grey cells. It is "up to them"-as you say over here.'"

Gyri: The plural of gyrus.

Gyrus: A convolution on the surface of a cerebral hemisphere caused by the infolding of the cerebral cortex. The gyri are bounded by crevices in the cortex called sulci. Many gyri are constant enough in their occurrence as anatomic features that they have been given names as, for example, the cingulate gyrus, the dentate gyrus, and so on. From the Greek gyros = a circle.

Heart: The muscle that pumps blood received from veins into arteries throughout the body. It is positioned in the chest behind the sternum (breastbone; in front of the trachea, esophagus, and aorta; and above the diaphragm muscle that separates the chest and abdominal cavities. The normal heart is about the size of a closed fist, and weighs about 10.5 ounces. It is cone-shaped, with the point of the cone pointing down to the left. Two-thirds of the heart lies in the left side of the chest with the balance in the right chest.
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Heart rate: The number of heart beats per unit time, usually per minute. The heart rate is based on the number of contractions of the ventricles (the lower chambers of the heart). The heart rate may be too fast (tachycardia) or too slow (bradycardia). The pulse is bulge of an artery from the wave of blood coursing through the blood vessel as a result of the heart beat. The pulse is often taken at the wrist to estimate the heart rate.

Hippocampus: An area buried deep in the forebrain that helps regulate emotion and memory. Functionally, the hippocampus is part of the olfactory cortex, that part of the cerebral cortex essential to the sense of smell. Certain antidepressants (such as fluoxetine, or Prozac) influence the birth of new neurons in the hippocampus. The hippocampus is so-called because its shape suggests that of a seahorse. From the Greek hippos (horse) = kampos (a sea monster).

Hypothalamus: The area of the brain that controls body temperature, hunger, and thirst.

Inflammation: A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response.
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Injury: Harm or hurt. The term "injury" may be applied in medicine to damage inflicted upon oneself as in a hamstring injury or by an external agent on as in a cold injury. The injury may be accidental or deliberate, as with a needlestick injury. The term "injury" may be synonymous (depending on the context) with a wound or with trauma.

Involuntary: Done other than in accordance with the conscious will of the individual. The opposite of voluntary.
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Leptomeninges: The two innermost layers of tissues that cover the brain and spinal cord. The two layers are called the arachnoid mater and pia mater.

Limb: The arm or leg.

Lobe: Part of an organ that appears to be separate in some way from the rest. A lobe may be demarcated from the rest of the organ by a fissure (crack), sulcus (groove), connective tissue or simply by its shape. For example, there are the frontal, parietal, temporal, and occipital lobes of the brain.
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Lumbar: Referring to the 5 lumbar vertebrae which are situated below the thoracic vertebrae and above the sacral vertebrae in the spinal column. The 5 lumbar vertebrae are represented by the symbols L1 through L5. There are correspondingly 5 lumbar nerves.

Medulla: The innermost part. The adrenal medulla is the innermost part of that gland. The renal medulla is the inner part of the kidney. The spinal medulla is the part of the spinal cord that is lodged within the vertebral canal.

Medulla oblongata: The base of the brain, which is formed by the enlarged top of the spinal cord. This part of the brain directly controls breathing, blood flow, and other essential functions.

Memory: 1. The ability to recover information about past events or knowledge. 2. The process of recovering information about past events or knowledge. 3. Cognitive reconstruction. The brain engages in a remarkable reshuffling process in an attempt to extract what is general and what is particular about each passing moment.
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Meninges: The three membranes that cover the brain and spinal cord (singular: meninx).
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Metabolism: The whole range of biochemical processes that occur within an organism. Metabolism consists both of anabolism and catabolism (the buildup and breakdown of substances, respectively). The biochemical reactions are known as metabolic pathways and involve enzymes that transform one substance into another substance, either breaking down a substance or building a new chemical substance. The term is commonly used to refer specifically to the breakdown of food and its transformation into energy.

Motor: In medicine, having to do with the movement of a part of the body. Something that produces motion or refers to motion. For example, a motor neuron is a nerve cell that conveys an impulse to a muscle causing it to contract. The term "motor" today is also applied to a nerve that signals a gland to secrete. Motor is as opposed to sensory.

Multiple sclerosis: Abbreviated MS. A disease of the central nervous system (CNS) marked by numbness, weakness, loss of muscle coordination, and problems with vision, speech, and bladder control. MS is an autoimmune disease in which the body's immune system attacks myelin, a key substance that serves as a nerve insulator and helps in the transmission of nerve signals. The progress, severity and specific symptoms in MS are unpredictable. One never knows when attacks will occur, how long they will last, or how severe they will be. Most people with MS are between the ages of 20 and 40 at the time of diagnosis. The term "multiple" refers to the multiple places in the CNS that are affected and to the multiple relapses and remissions characteristic of MS.
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Muscle: Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart muscle is called "cardiac muscle." Muscle that is in the walls of arteries and bowel is called "smooth muscle."

Myelin: The fatty substance that covers and protects nerves. Myelin is a layered tissue that sheathes the axons (nerve fibers). This sheath around the axon acts like a conduit in an electrical system, ensuring that messages sent by axons are not lost en route. It allows efficient conduction of action potentials down the axon. Myelin consists of 70% lipids (cholesterol and phospholipid) and 30% proteins. It is produced by oligodendrocytes in the central nervous system.

Neck: The part of the body joining the head to the shoulders. Also, any narrow or constricted part of a bone or organ that joins its parts as, for example, the neck of the femur bone.

Nerve: A bundle of fibers that uses chemical and electrical signals to transmit sensory and motor information from one body part to another. See: Nervous system.

Nerve cell: See: Neuron.

Neurology: The medical specialty concerned with the diagnosis and treatment of disorders of the nervous system -- the brain, the spinal cord, and the nerves.
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Neuron: A nerve cell that sends and receives electrical signals over long distances within the body. A neuron may send electrical output signals to muscle neurons (called motor neurons or motoneurons) and to other neurons. A neuron may receive electrical input signals from sensory cells (called sensory neurons) and from other neurons. A neuron that simply signals another neuron is called an interneuron.
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Nuclei: The plural of nucleus.

Nucleus: 1) In cell biology, the structure that houses the chromosomes. 2) In neuroanatomy, a group of nerve cells.

Occipital: 1. Pertaining to the occiput, the back of head.
2. Located near the occipital bone as, for example, the occipital lobe of the brain.

Ophthalmoscope: A lighted instrument, one of the most important tools of the physician, used to examine the interior of the eye, including the lens, retina and optic nerve.
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Optic: Having to do with vision.

Optic nerve: The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images. Using an ophthalmoscope, the head of the optic nerve can be easily seen. It can be viewed as the only visible part of the brain (or extension of it).
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Pain: An unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibers that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.
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Paralysis: Loss of voluntary movement (motor function). Paralysis that affects only one muscle or limb is partial paralysis, also known as palsy; paralysis of all muscles is total paralysis, as may occur in cases of botulism.

Parietal: Adjective from the Latin "parietalis" meaning "belonging to the wall" that the ancient anatomists used to designate the wall, as of a body cavity.
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Parietal lobe: Part of the brain, specifically the section of the cerebral hemisphere that lies beneath the parietal bone, the main side bone of the skull.
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Pelvic: Having to do with the pelvis, the lower part of the abdomen, located between the hip bones.

Peripheral: Situated away from the center, as opposed to centrally located.
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Peripheral nervous system (PNS): That portion of the nervous system that is outside the brain and spinal cord.
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Pharmacy: A location where prescription drugs are sold. A pharmacy is, by law, constantly supervised by a licensed pharmacist.

Pituitary: 1. As an adjective, pertaining to the pituitary gland or its hormonal secretions. 2. As a noun, the pituitary gland itself.
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Pituitary gland: The main endocrine gland. It is a small structure in the head. It is called the master gland because it produces hormones that control other glands and many body functions including growth. The pituitary consists of the anterior and posterior pituitary.
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Pons: A specific section of the brain formed by the rounded prominence on the front surface of the brainstem. (The brainstem is the lowest part of the brain that merges with the spinal cord; it consists of a structure called the medulla oblongata, the midbrain and the pons.) Cranial nerves V, VI, VII and VIII take origin at the border of the pons.
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Posterior: The back or behind, as opposed to the anterior.
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Putamen: An area in the brain within a structure called the lentiform nucleus. The putamen may decrease in size as a result of damage in Huntington's disease.
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Reflex: A reaction that is involuntary. The corneal reflex is the blink that occurs with irritation of the eye. The nasal reflex is a sneeze.

Respiration: 1. The act of inhaling and exhaling air in order to exchange oxygen for carbon dioxide. Synonymous with breathing and ventilation. 2. The cellular metabolic process by which oxygen is taken in, substances are oxidized, energy is released, and carbon dioxide and oxidized products are given off.

Sacral: Referring to the sacrum, the 5 vertebral bones situated between the lumbar vertebrae and the coccyx (the lowest segment of the vertebral column). The 5 sacral vertebrae are represented by the symbols S1 through S5. There are correspondingly 5 sacral nerves. The sacral vertebrae are normally fused to form the sacrum.

Sclerosis: Localized hardening of skin.

Sensation: In medicine and physiology, sensation refers to the registration of an incoming (afferent) nerve impulse in that part of the brain called the sensorium, which is capable of such perception. Therefore, the awareness of a stimulus as a result of its perception by sensory receptors. (Sensory is here synonymous with sensation.)
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Sensory: Relating to sensation, to the perception of a stimulus and the voyage made by incoming (afferent) nerve impulses from the sense organs to the nerve centers.
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Spinal cord: The major column of nerve tissue that is connected to the brain and lies within the vertebral canal and from which the spinal nerves emerge. Thirty-one pairs of spinal nerves originate in the spinal cord: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The spinal cord and the brain constitute the central nervous system (CNS). The spinal cord consists of nerve fibers that transmit impulses to and from the brain. Like the brain, the spinal cord is covered by three connective-tissue envelopes called the meninges. The space between the outer and middle envelopes is filled with cerebrospinal fluid (CSF), a clear colorless fluid that cushions the spinal cord against jarring shock. Also known simply as the cord.
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Spine: 1) The column of bone known as the vertebral column, which surrounds and protects the spinal cord. The spine can be categorized according to level of the body: i.e., cervical spine (neck), thoracic spine (upper and middle back), and lumbar spine (lower back). See also vertebral column. 2) Any short prominence of bone. The spines of the vertebrae protrude at the base of the back of the neck and in the middle of the back. These spines protect the spinal cord from injury from behind.

Stress: Forces from the outside world impinging on the individual. Stress is a normal part of life that can help us learn and grow. Conversely, stress can cause us significant problems.
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Striatum: Part of the basal ganglia of the brain. The basal ganglia are interconnected masses of gray matter located in the interior regions of the cerebral hemispheres and in the upper part of the brainstem.
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Subarachnoid: Literally, beneath the arachnoid, the middle of three membranes that cover the central nervous system. In practice, subarachnoid usually refers to the space between the arachnoid and the pia mater, the innermost membrane surrounding the central nervous system.
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Sulci: The plural of sulcus.

Taste: Taste belongs to our chemical sensing system, or the chemosenses. The complicated process of tasting begins when molecules released by the substances stimulate special cells in the mouth or throat. These special sensory cells transmit messages through nerves to the brain where specific tastes are identified.
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Temporal: 1. Pertaining to time, limited in time, temporary, or transient.
2. Pertaining to the temple region of the head. The temporal lobe of the brain is located beneath the temple.
From the Latin tempus which means both time and the temple of the head.

Temporal lobe: The lobe of the cerebral hemisphere located down on the side just forward of the occipital lobe. The temporal lobe contains the auditory cortex which is responsible for hearing. It is also the site of the seizure activity characteristic of temporal-lobe epilepsy.

Therapeutics: In medicine, the branch that deals specifically with the treatment of disease and the art and science of healing.
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Thoracic: Pertaining to the chest.

Ventricles: 1, The right ventricle and the left ventricle, the lower two chambers of the heart. 2. Two or more of the four connected spaces within the central portion of the brain.

Vertebrae: The preferred plural of vertebra. (The alternate plural is vertebras.) See also: Cervical vertebrae; Coccygeal vertebrae; Lumbar vertebrae; Sacral vertebrae; and Thoracic vertebrae.

Vital: Necessary to maintain life. Breathing is a vital function.

Voluntary: Done in accordance with the conscious will of the individual. The opposite of involuntary.
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White matter: The part of the brain that contains myelinated nerve fibers. The white matter is white because it is the color of myelin, the insulation covering the nerve fibers. The white matter is as opposed to the gray matter (the cortex of the brain which contains nerve cell bodies).