Brain Facts A Primer on the Brain and Nervous System by The Society for Neuroscience (z-lib.org)

Glossary

ACETYLCHOLINE A neurotransmitter in both the brain, where it AUTONOMIC NERVOUS SYSTEM A part of the peripheral ner-
regulates memory, and in the peripheral nervous system, vous system responsible for regulating the activity of internal
where it controls the actions of skeletal and smooth muscle. organs. It includes the sympathetic and parasympathetic ner-
ACTION POTENTIAL This occurs when a neuron is activated and vous systems.
temporarily reverses the electrical state of its interior mem- AXON The fiberlike extension of a neuron by which the cell
brane from negative to positive. This electrical charge travels sends information to target cells.
along the axon to the neuron’s terminal where it triggers the BASAL GANGLIA Clusters of neurons, which include the cau-
release of a neurotransmitter. date nucleus, putamen, globus pallidus and substantia nigra,
ADRENAL CORTEX An endocrine organ that secretes corticos- located deep in the brain that play an important role in move-
teroids for metabolic functions; for example, in response to ment. Cell death in the substantia nigra contributes to Parkin-
stress. son’s disease.
ADRENAL MEDULLA An endocrine organ that secretes epineph- BRAINSTEM The major route by which the forebrain sends
rine and norepinephrine in concert with the activation of the information to and receives information from the spinal cord
sympathetic nervous system; for example, in response to stress. and peripheral nerves. The brainstem controls, among other
AGONIST A neurotransmitter, a drug or other molecule that things, respiration and regulation of heart rhythms.
stimulates receptors to produce a desired reaction. BROCA’S AREA The brain region located in the frontal lobe of
ALZHEIMER’S DISEASE The major cause of dementia most the left hemisphere that is important for the production of
prevalent in the elderly, it inflicts enormous human financial speech.
cost on society. The disease is characterized by death of neu- CATECHOLAMINES The neurotransmitters dopamine, epineph-
rons in the hippocampus, cerebral cortex and other brain rine and norepinephrine that are active both in the brain and
regions. the peripheral sympathetic nervous system. These three mole-
AMINO ACID TRANSMITTERS The most prevalent neurotrans- cules have certain structural similarities and are part of a
mitters in the brain, these include glutamate and aspartate, larger class of neurotransmitters known as monoamines.
which have excitatory actions, and glycine and gamma-amino CEREBELLUM A large structure located at the roof of the hind-
butyric acid (GABA), which have inhibitory actions. brain that helps control movement by making connections to
AMYGDALA A structure in the forebrain that is an important the pons, medulla, spinal cord and thalamus. It also may be
component of the limbic system and plays a central role in involved in aspects of motor learning.
emotional learning. CEREBRAL CORTEX The outermost layer of the cerebral hemi-
ANDROGENS Sex steroid hormones, including testosterone, spheres of the brain. It is responsible for all forms of conscious
found in higher levels in males than females. They are respon- experience, including perception, emotion, thought and plan-
sible for male sexual maturation. ning.
ANTAGONIST A drug or other molecule that blocks receptors. CEREBRAL HEMISPHERES The two specialized halves of the
Antagonists inhibit the e∑ects of agonists. brain. The left hemisphere is specialized for speech, writing,
APHASIA Disturbance in language comprehension or produc- language and calculation; the right hemisphere is specialized
tion, often as a result of a stroke. for spatial abilities, face recognition in vision and some aspects
AUDITORY NERVE A bundle of nerve fibers extending from the of music perception and production.
cochlea of the ear to the brain, which contains two branches: CEREBROSPINAL FLUID A liquid found within the ventricles of
the cochlear nerve that transmits sound information and the the brain and the central canal of the spinal cord.
vestibular nerve that relays information related to balance. CHOLECYSTOKININ A hormone released from the lining of the

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stomach during the early stages of digestion which acts as a DRUG ADDICTION Loss of control over drug intake or compul-
powerful suppressant of normal eating. It also is found in the sive seeking and taking of drugs, despite adverse consequences.
brain. ENDOCRINE ORGAN An organ that secretes a hormone directly
CIRCADIAN RHYTHM A cycle of behavior or physiological into the bloodstream to regulate cellular activity of certain
change lasting approximately 24 hours. other organs.
CLASSICAL CONDITIONING Learning in which a stimulus that ENDORPHINS Neurotransmitters produced in the brain that
naturally produces a specific response (unconditioned stimu- generate cellular and behavioral e∑ects like those of morphine.
lus) is repeatedly paired with a neutral stimulus (conditioned EPILEPSY A disorder characterized by repeated seizures,
stimulus). As a result, the conditioned stimulus can evoke a which are caused by abnormal excitation of large groups of
response similar to that of the unconditioned stimulus. neurons in various brain regions. Epilepsy can be treated with
COCHLEA A snail-shaped, fluid-filled organ of the inner ear many types of anticonvulsant medications.
responsible for transducing motion into neurotransmission to EPINEPHRINE A hormone, released by the adrenal medulla
produce an auditory sensation. and specialized sites in the brain, that acts with norepineph-
COGNITION The process or processes by which an organism rine to a∑ect the sympathetic division of the autonomic ner-
gains knowledge or becomes aware of events or objects in its vous system. Sometimes called adrenaline.
environment and uses that knowledge for comprehension and ESTROGENS A group of sex hormones found more abun-
problem-solving. dantly in females than males. They are responsible for female
CONE A primary receptor cell for vision located in the retina. sexual maturation and other functions.
The cone is sensitive to color and used primarily for daytime EVOKED POTENTIALS A measure of the brain’s electrical activ-
vision. ity in response to sensory stimuli. This is obtained by placing
CORPUS CALLOSUM The large bundle of nerve fibers linking electrodes on the surface of the scalp (or more rarely, inside
the left and right cerebral hemispheres. the head), repeatedly administering a stimulus and then using
CORTISOL A hormone manufactured by the adrenal cortex. In a computer to average the results.
humans, cortisol is secreted in greatest quantities before EXCITATION A change in the electrical state of a neuron that
dawn, readying the body for the activities of the coming day. is associated with an enhanced probability of action potentials.
DEPRESSION A mental disorder characterized by depressed FOLLICLE-STIMULATING HORMONE A hormone released by the
mood and abnormalities in sleep, appetite and energy level. pituitary gland that stimulates the production of sperm in the
DENDRITE A tree-like extension of the neuron cell body. Along male and growth of the follicle (which produces the egg) in
with the cell body, it receives information from other neurons. the female.
DOPAMINE A catecholamine neurotransmitter known to FOREBRAIN The largest division of the brain, which includes
have multiple functions depending on where it acts. the cerebral cortex and basal ganglia. The forebrain is cred-
Dopamine-containing neurons in the substantia nigra of the ited with the highest intellectual functions.
brainstem project to the caudate nucleus and are destroyed FRONTAL LOBE One of the four divisions (parietal, temporal,
in Parkinson’s victims. Dopamine is thought to regulate occipital) of each hemisphere of the cerebral cortex. The
emotional responses and play a role in schizophrenia and frontal lobe has a role in controlling movement and in the
drug abuse. planning and coordinating of behavior.
DORSAL HORN An area of the spinal cord where many nerve GAMMA-AMINO BUTYRIC ACID (GABA) An amino acid trans-
fibers from peripheral pain receptors meet other ascending mitter in the brain whose primary function is to inhibit the
and descending nerve fibers. firing of neurons.

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GLIA Specialized cells that nourish and support neurons. MANIA A mental disorder characterized by excessive excite-
GLUTAMATE An amino acid neurotransmitter that acts to ment, exalted feelings, elevated mood, psychomotor over-
excite neurons. Glutamate stimulates N-methyl-D-aspartate activity and overproduction of ideas. It may be associated
(NMDA) receptors that have been implicated in activities with psychosis; for example, delusions of grandeur.
ranging from learning and memory to development and MELATONIN Produced from serotonin, melatonin is released
specification of nerve contacts in a developing animal. Stimu- by the pineal gland into the bloodstream. Melatonin a∑ects
lation of NMDA receptors may promote beneficial changes, physiological changes related to time and lighting cycles.
while overstimulation may be a cause of nerve cell damage or MEMORY CONSOLIDATION The physical and psychological
death in neurological trauma and stroke. changes that take place as the brain organizes and restruc-
GONAD Primary sex gland: testis in the male and ovary in the tures information in order to make it a permanent part of
female. memory.
GROWTH CONE A distinctive structure at the growing end of METABOLISM The sum of all physical and chemical changes
most axons. It is the site where new material is added to the that take place within an organism and all energy transforma-
axon. tions that occur within living cells.
HIPPOCAMPUS A seahorse-shaped structure located within MIDBRAIN The most anterior segment of the brainstem.
the brain and considered an important part of the limbic sys- Along with the pons and medulla, the midbrain is involved in
tem. It functions in learning, memory and emotion. many functions, including regulation of heart rate, respira-
HORMONES Chemical messengers secreted by endocrine tion, pain perception and movement.
glands to regulate the activity of target cells. They play a role MITOCHONDRIA Small cylindrical particles inside cells that
in sexual development, calcium and bone metabolism, growth provide energy for the cell by converting sugar and oxygen
and many other activities. into special energy molecules, called ATP.
HUNTINGTON’S DISEASE A movement disorder caused by MONOAMINE OXIDASE (MAO) The brain and liver enzyme that
death of neurons in the basal ganglia and other brain regions. normally breaks down the catecholamines norepinephrine,
It is characterized by abnormal movements called chorea— dopamine, and epinephrine and other monosomines such as
sudden, jerky movements without purpose. serotonin.
HYPOTHALAMUS A complex brain structure composed of MOTOR NEURON A neuron that carries information from the
many nuclei with various functions. These include regulating central nervous system to muscle.
the activities of internal organs, monitoring information from MYASTHENIA GRAVIS A disease in which acetylcholine recep-
the autonomic nervous system, controlling the pituitary gland tors on muscle cells are destroyed so that muscles can no
and regulating sleep and appetite. longer respond to the acetylcholine signal in order to con-
INHIBITION In reference to neurons, it is a synaptic message tract. Symptoms include muscular weakness and progressively
that prevents the recipient cell from firing. more common bouts of fatigue. The disease’s cause is unknown
IONS Electrically charged atoms or molecules. but is more common in females than in males and usually
LIMBIC SYSTEM A group of brain structures—including the strikes between the ages of 20 and 50.
amygdala, hippocampus, septum, basal ganglia and others— MYELIN Compact fatty material that surrounds and insulates
that help regulate the expression of emotion and emotional axons of some neurons.
memory. NERVE GROWTH FACTOR A substance whose role is to guide
LONG-TERM MEMORY The final phase of memory in which neuronal growth during embryonic development, especially
information storage may last from hours to a lifetime. in the peripheral nervous system. Nerve growth factor also

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probably helps sustain neurons in the adult. to be a necessary step in allowing some neurotransmitters to
NEURON Nerve cell. It is specialized for the transmission of act and is often the result of second messenger activity.
information and characterized by long fibrous projections PINEAL GLAND An endocrine organ found in the brain. In
called axons and shorter, branch-like projections called some animals, the pineal gland serves as a light-influenced
dendrites. biological clock.
NEUROTRANSMITTER A chemical released by neurons at a PITUITARY GLAND An endocrine organ closely linked with the
synapse for the purpose of relaying information to other hypothalamus. In humans, the gland is composed of two lobes
neurons via receptors. and secretes a number of hormones that regulate the activity
NOCICEPTORS In animals, nerve endings that signal the sensa- of other endocrine organs in the body.
tion of pain. In humans, they are called pain receptors. PONS A part of the hindbrain that, with other brain struc-
NOREPINEPHRINE A catecholamine neurotransmitter, pro- tures, controls respiration and regulates heart rhythms. The
duced both in the brain and in the peripheral nervous system. pons is a major route by which the forebrain sends informa-
It is involved in arousal, and regulation of sleep, mood and tion to and receives information from the spinal cord and
blood pressure. peripheral nervous system.
OCCIPITAL LOBE One of the four subdivisions of the cerebral PSYCHOSIS A severe symptom of mental disorders character-
cortex. The occipital lobe plays a role in processing visual ized by an inability to perceive reality. It can occur in many
information. conditions, including schizophrenia, mania, depression and
ORGANELLES Small structures within a cell that maintain the drug-induced states.
cells and do the cells’ work. RECEPTOR CELL A specialized sensory cell designed to pick up
PARASYMPATHETIC NERVOUS SYSTEM A branch of the auto- and transmit sensory information.
nomic nervous system concerned with the conservation of the RECEPTOR MOLECULE A specific protein on the surface or
body’s energy and resources during relaxed states. inside of a cell with a characteristic chemical and physical
PARIETAL LOBE One of the four subdivisions of the cerebral structure. Many neurotransmitters and hormones exert their
cortex. The parietal lobe plays a role in sensory processes, e∑ects by binding to receptors on cells.
attention and language. REUPTAKE A process by which released neurotransmitters are
PARKINSON’S DISEASE A movement disorder caused by death absorbed for subsequent reuse.
of dopamine neurons in the substantia nigra located in the ROD A sensory neuron located in the periphery of the retina.
midbrain. Symptoms include tremor, shuΩing gait and gen- The rod is sensitive to light of low intensity and specialized
eral paucity of movement. for nighttime vision.
PEPTIDES Chains of amino acids that can function as neuro- SCHIZOPHRENIA A chronic mental disorder characterized by
transmitters or hormones. psychosis (e.g., hallucinations and delusions), flattened emo-
PERIPHERAL NERVOUS SYSTEM A division of the nervous sys- tions and impaired cognitive function.
tem consisting of all nerves that are not part of the brain or SECOND MESSENGERS Substances that trigger communi-
spinal cord. cations among di∑erent parts of a neuron. These chemicals
PHOSPHORYLATION A process that modifies the properties of play a role in the manufacture and release of neurotransmit-
neurons by acting on an ion channel, neurotransmitter receptor ters, intracellular movements, carbohydrate metabolism and
or other regulatory protein. During phosphorylation, a phos- processes of growth and development. The messengers direct
phate molecule is placed on a protein and results in the activa- e∑ects on the genetic material of cells may lead to long-term
tion or inactivation of the protein. Phosphorylation is believed alterations of behavior, such as memory and drug addiction.

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SEROTONIN A monoamine neurotransmitter believed to play SYMPATHETIC NERVOUS SYSTEM A branch of the autonomic
many roles, including, but not limited to, temperature regula- nervous system responsible for mobilizing the body’s energy
tion, sensory perception and the onset of sleep. Neurons and resources during times of stress and arousal.
using serotonin as a transmitter are found in the brain and in SYNAPSE A gap between two neurons that functions as the
the gut. A number of antidepressant drugs are targeted to site of information transfer from one neuron to another.
brain serotonin systems. TEMPORAL LOBE One of the four major subdivisions of each
SHORT-TERM MEMORY A phase of memory in which a limited hemisphere of the cerebral cortex. The temporal lobe func-
amount of information may be held for several seconds to tions in auditory perception, speech and complex visual per-
minutes. ceptions.
STIMULUS An environmental event capable of being detected THALAMUS A structure consisting of two egg-shaped masses
by sensory receptors. of nerve tissue, each about the size of a walnut, deep within
STROKE The third largest cause of death in America, stroke the brain. The key relay station for sensory information
is an impeded blood supply to the brain. Stroke can be caused flowing into the brain, the thalamus filters out only informa-
by a rupture of a blood vessel wall, an obstruction of blood tion of particular importance from the mass of signals enter-
flow caused by a clot or other material or by pressure on a ing the brain.
blood vessel (as by a tumor). Deprived of oxygen, which is VENTRICLES Of the four ventricles, comparatively large spaces
carried by blood, nerve cells in the a∑ected area cannot func- filled with cerebrospinal fluid, three are located in the fore-
tion and die. Thus, the part of the body controlled by those brain and one in the brainstem. The lateral ventricles, the two
cells cannot function either. Stroke can result in loss of con- largest, are symmetrically placed above the brainstem, one in
sciousness and death. each hemisphere.
WERNICKE’S AREA A brain region responsible for the compre-
hension of language and the production of meaningful
speech.

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Index

Numbers in bold refer to illustrations.

Acetylcholine 4 Down syndrome 40–41 Magnetoencephalography Pons 3, 23
Action potential 4 Drug reward system 34 (MEG) 44 Positron emission tomography
Addiction 33–36 Endocrine system 6–7, 25–27
Aging 28–29 Endorphins 6, 17 Marijuana 36 (PET) 19, 43
Epilepsy 31–32 Memory 18–19 Primary visual cortex 12
and intellectual capacity 29 Epinephrine 25–26 Methylprednisolone 39 Procedural knowledge 18
AIDS 40 Estrogen 7 Midbrain 3, 8 Prostaglandins 17, 31
Alcohol 34–36 Fetal alcohol syndrome 35 Mitochondria 45 Psychostimulants 34–35
Alpha motor neurons 20 Firing of neurons 4–5 Monoamine oxidase inhibitors Receptive field 12
Alzheimer’s disease 36–37 Flexion withdrawal 20–21 Receptors 4
Amino acid transmitters 4–5 Fluoxetine 32 (MAOIs) 32 Reflex 20–21
Amphetamines 34 Forebrain 3 Morphine 6, 30, 31, 34 Regeneration 46
Amyloid protein 36–37 Functional Magnetic Reso- Motor cortex 3, 20 Reproduction 7
Amyotrophic lateral sclerosis Motor neuron 20 Schizophrenia 39–40
nance Imaging (fMRI) 44 Motor unit 20 Second messengers 7
(ALS) 42 Gamma-amino butyric acid Movement 20–21 Selye, Hans 25
Analgesia 30 MPTP 30 Serotonin 6, 32
Androgen 7 (GABA) 5, 24, 32, 35 Multiple sclerosis 40 Single photon emission
Anxiety disorders 39 Gamma motor neurons 20 Myasthenia gravis 4
Autoimmune response 27 Gene 45 Myelin 4–5 computed tomography
Autonomic nervous system Narcolepsy 24 (SPECT) 43
diagnosis 44– 45 Nerve growth factor (NGF) 46 Sleep 22–24
11, 25 therapy 46–47 Nerve impulse 4, 5 REM sleep 22–24
Axon 4 –5 Glucocorticoids 7, 26–27 Neurofibrillary tangles 36 stages 22
Basal ganglia 19, 21, 30 Glutamate 5, 36, 38 Neurological trauma 38–39 disorders 23–24
Biological clock 7, 27 Hearing 14–15 Neuron 4–5 Smell 15–16
Brain Heroin 34 Spinal cord 6, 11, 17, 20–21,
Hippocampus 3, 18–19, 27 birth 9–10 38–39, 46
aging 28–29 Huntington’s disease 41 migration 9–10 Strabismus 14
anatomical organization 3 Hypothalamus 3, 7, 24, 32 pathfinding 10 Stress 25–27
development 8–11 Immune system 27 survival 10–11 in arousal 25–26
diseases 2–3 Information processing, Neurotransmitters 4 –7 chronic 27
tumors 42 and hearing 14–15 Nicotine 33–34 and endocrine system 25–27
Broca’s area 19 and learning and memory NMDA receptors 5, 18 and schizophrenia 39
Catecholamines 6 Norepinephrine 6 Stroke 37–38
Central nervous system 6, 11 18–19 Obsessive-compulsive Substance P 6
Cerebellum 19, 21 and movement 20–21 disorder 39 Synapse 4, 5, 29
Cerebral cortex and pain 16–17 Occipital lobe 3, 12 Taste 15–16
3, 17, 19, 23, 31 and taste and smell 15–16 Olfactory bulbs 15–16 Temporal lobe 3, 18
Club drugs 36 and vision 12–13 Opiates 34–35 Testosterone 7
Cocaine 34–35 Inhibitory neurons 20–21 Pain 16–17, 30–31 Thalamus 3
Cortisol 25–26 Ion channels 4 Panic disorder 39 Touch 16–17
Costs of brain diseases 2–3 Language 19 Parietal lobe 3 Tourette syndrome 41– 42
Crossed extension reflex 20–21 Learning 18–19 Parkinson’s disease 30, Tricyclic antidepressants 32
Declarative knowledge 18 Learning disorders 37 46–47 Trophic factors 6, 46
Dementia 28, 36 Levodopa 6, 30 Peptides 6 Vision 12, 13 –15
Dendrite 4–5 Limbic system 15 Peripheral nervous system 11 Wernicke’s area 19
Depression Long-term potentiation 18 Phenytoin 31 Working memory 18
major 32 Lou Gehrig’s disease 42 Phobias 39
manic 32 Magnetic resonance imaging Pituitary gland 6, 7, 32
Dopamine 6, 30, 34 (MRI) 43– 44

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