B Spot Brain Glossary

B Spot Brain Glossary


ACETYLCHOLINE A neurotransmitter active both in the brain,

where it regulates memory, and in the peripheral nervous system,

where it controls the actions of skeletal and smooth muscle.

ACTION POTENTIAL An electrical charge that travels along the

axon to the neuron’s terminal, where it triggers the release of a

neurotransmitter. This occurs when a neuron is activated and temporarily

reverses the electrical state of its interior membrane from

negative to positive.

ADRENAL CORTEX An endocrine organ that secretes steroid hormones

for metabolic functions; for example, in response to stress.

ADRENAL MEDULLA An endocrine organ that secretes epinephrine

and norepinephrine in concert with the activation of the

sympathetic nervous system; for example, in response to stress.

AGONIST 1.) A neurotransmitter, drug, or other molecule that

stimulates receptors to produce a desired reaction. 2.) A muscle

that moves a joint in an intended direction.

ALZHEIMER’S DISEASE A major cause of dementia in the elderly,

this neurodegenerative disorder is characterized by the death of neurons

in the hippocampus, cerebral cortex, and other brain regions.

AMINO ACID TRANSMITTERS The most prevalent neurotransmitters

in the brain, these include glutamate and aspartate, which have

excitatory actions on nerve cells, and glycine and gamma-amino

butyric acid (GABA), which have inhibitory actions on nerve cells.

AMYGDALA A structure in the forebrain that is an important component

of the limbic system and plays a central role in emotional

learning, particularly within the context of fear.

ANDROGENS Sex steroid hormones, including testosterone, found

in higher levels in males than females. They are responsible for

male sexual maturation.

ANTAGONIST 1.) A drug or other molecule that blocks receptors.

Antagonists inhibit the effects of agonists. 2.) A muscle that moves

a joint in opposition to an intended direction.

APHASIA Disturbance in language comprehension or production,

often as a result of a stroke.

APOPTOSIS Programmed cell death induced by specialized biochemical

pathways, often serving a specific purpose in the development

of the animal.

AUDITORY NERVE A bundle of nerve fibers extending from the

cochlea of the ear to the brain that contains two branches: the cochlear

nerve, which transmits sound information, and the vestibular

nerve, which relays information related to balance.

AUTONOMIC NERVOUS SYSTEM A part of the peripheral nervous

system responsible for regulating the activity of internal organs.

It includes the sympathetic and parasympathetic nervous systems.

AXON The fiberlike extension of a neuron by which it sends information

to target cells.

BASAL GANGLIA Structures located deep in the brain that play

an important role in the initiation of movements. These clusters of

neurons include the caudate nucleus, putamen, globus pallidus, and

substantia nigra. Cell death in the substantia nigra contributes to

Parkinson’s disease.

BRAINSTEM The major route by which the forebrain sends

information to and receives information from the spinal cord and

peripheral nerves. The brainstem controls, among other things,

respiration and the regulation of heart rhythms.

BROCA’S AREA The brain region located in the frontal lobe of the

left hemisphere that is important for the production of speech.

CATECHOLAMINES The neurotransmitters dopamine, epinephrine,

and norepinephrine, which are active in both the brain and

the peripheral sympathetic nervous system. These three molecules

have certain structural similarities and are part of a larger class of

neurotransmitters known as monoamines.

CEREBELLUM A large structure located at the roof of the hindbrain

that helps control the coordination of movement by making connections

to the pons, medulla, spinal cord, and thalamus. It also

may be involved in aspects of motor learning.

CEREBRAL CORTEX The outermost layer of the cerebral hemispheres

of the brain. It is largely responsible for all forms of conscious

experience, including perception, emotion, thought, and planning.

CEREBRAL HEMISPHERES The two specialized halves of the brain.

For example, in right-handed people, the left hemisphere is specialized

for speech, writing, language, and calculation; the right hemisphere

is specialized for spatial abilities, visual face recognition, and

some aspects of music perception and production.

CEREBROSPINAL FLUID A liquid found within the ventricles of

the brain and the central canal of the spinal cord.

CIRCADIAN RHYTHM A cycle of behavior or physiological change

lasting approximately 24 hours.

CLASSICAL CONDITIONING Learning in which a stimulus that

naturally produces a specific response (unconditioned stimulus) is

repeatedly paired with a neutral stimulus (conditioned stimulus).

As a result, the conditioned stimulus can come to evoke a response

similar to that of the unconditioned stimulus.

COCHLEA A snail-shaped, fluid-filled organ of the inner ear responsible

for converting sound into electrical potentials to produce

an auditory sensation.

COGNITION The process or processes by which an organism gains

knowledge or becomes aware of events or objects in its environment

and uses that knowledge for comprehension and problem-solving.

CONE A primary receptor cell for vision located in the retina. It is

sensitive to color and is used primarily for daytime vision.

CORPUS CALLOSUM The large bundle of nerve fibers linking the

left and right cerebral hemispheres.

CORTISOL A hormone manufactured by the adrenal cortex. In

humans, cortisol is secreted in the greatest quantities before dawn,

readying the body for the activities of the coming day.

CRANIAL NERVE A nerve that carries sensory input and motor

output for the head and neck region. There are 12 cranial nerves.

DEPRESSION A mental disorder characterized by sadness, hopelessness,

pessimism, loss of interest in life, reduced emotional wellbeing,

and abnormalities in sleep, appetite, and energy level.

DENDRITE A treelike extension of the neuron cell body. The dendrite

is the primary site for receiving and integrating information

from other neurons.

DOPAM INE A catecholamine neurotransmitter known to have

varied functions depending on where it acts. Dopamine-containing

neurons in the substantia nigra of the brainstem project to the caudate

nucleus and are destroyed in Parkinson’s victims. Dopamine

is thought to regulate key emotional responses and plays a role in

schizophrenia and drug abuse.

DORSAL HORN An area of the spinal cord where many nerve

fibers from peripheral sensory receptors meet other ascending and

descending nerve fibers.

DRUG ADDICTION Loss of control over drug intake or compulsive

seeking and taking of drugs, despite adverse consequences.

ENDOCRINE ORGAN An organ that secretes a hormone directly

into the bloodstream to regulate cellular activity of certain

other organs.

ENDORPHINS Neurotransmitters produced in the brain that generate

cellular and behavioral effects like those of morphine.

EPILEPSY A disorder characterized by repeated seizures, which are

caused by abnormal excitation of large groups of neurons in various

brain regions. Epilepsy can be treated with many types of anticonvulsant


EPINEPHRINE A hormone, released by the adrenal medulla and

specialized sites in the brain, that acts with norepinephrine to affect

the sympathetic division of the autonomic nervous system. Sometimes

called adrenaline.

ESTROGENS A group of sex hormones found more abundantly in

females than males. They are responsible for female sexual maturation

and other functions.

EVOKED POTENTIAL A measure of the brain’s electrical activity in

response to sensory stimuli. This is obtained by placing electrodes

on the surface of the scalp (or more rarely, inside the head), repeatedly

administering a stimulus, and then using a computer to average

the results.

EXCITATION A change in the electrical state of a neuron that is

associated with an enhanced probability of action potentials.


by the pituitary gland that stimulates the production of sperm in

the male and growth of the follicle (which produces the egg) in

the female.

FOREBRAIN The largest part of the brain, which includes the

cerebral cortex and basal ganglia. The forebrain is credited with the

highest intellectual functions.

FOVEA The centermost part of the eye located in the center of the

retina and that contains only cone photoreceptors.

FRONTAL LOBE One of the four subdivisions of the cerebral cortex.

The frontal lobe has a role in controlling movement and in the

planning and coordinating of behavior.

GAMMA-AMINO BUTYRIC ACID (GABA) An amino acid transmitter

in the brain whose primary function is to inhibit the firing of

nerve cells.

GLIA Specialized cells that nourish and support neurons.

GLUTAMATE An amino acid neurotransmitter that acts to excite

neurons. Glutamate stimulates N-methyl-d-aspartate (NMDA)

and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid

(AMPA). AMPA receptors have been implicated in activities ranging

from learning and memory to development and specification

of nerve contacts in developing animals. Stimulation of NMDA

receptors may promote beneficial changes, whereas overstimulation

may be a cause of nerve cell damage or death in neurological

trauma and stroke.

GONAD Primary sex gland: testis in the male and ovary in

the female.

GROWTH CONE A distinctive structure at the growing end of

most axons. It is the site where new material is added to the axon.

HAIR CELLS Sensory receptors in the cochlea that convert mechanical

vibration to an electrical signal; they in turn excite

the 30,000 fibers of the auditory nerve that carry the signals to

the brainstem.

HIPPOCAMPUS A seahorse-shaped structure located within the

brain and considered an important part of the limbic system. One

of the most studied areas of the brain, it functions in learning,

memory, and emotion.

HOMEOSTASIS The normal equilibrium of body function.

HORMONES Chemical messengers secreted by endocrine glands

to regulate the activity of target cells. They play a role in sexual

development, calcium and bone metabolism, growth, and many

other activities.

HUNTINGTON’S DISEASE A movement disorder caused by the

death of neurons in the basal ganglia and other brain regions. It is

characterized by abnormal movements called chorea — sudden,

jerky movements without purpose.

HYPOTHALAMUS A complex brain structure composed of many

nuclei with various functions, including regulating the activities

of internal organs, monitoring information from the autonomic

nervous system, controlling the pituitary gland, and regulating sleep

and appetite.

INTERNEURON A neuron that exclusively signals another neuron.

INHIBITION A synaptic message that prevents a recipient neuron

from firing.

IONS Electrically charged atoms or molecules.

LIMBIC SYSTEM A group of brain structures — including the

amygdala, hippocampus, septum, basal ganglia, and others — that

help regulate the expression of emotion and emotional memory.

LONG-TERM MEMORY The final phase of memory, in which

information storage may last from hours to a lifetime.

MANIA A mental disorder characterized by excessive excitement,

exalted feelings, elevated mood, psychomotor overactivity, and

overproduction of ideas. It may be associated with psychosis; for

example, delusions of grandeur.

MEMORY CONSOLIDATION The physical and psychological

changes that take place as the brain organizes and restructures

information to make it a permanent part of memory.

METABOLISM The sum of all physical and chemical changes that

take place within an organism and all energy transformations that

occur within living cells.

MIDBRAIN The most anterior segment of the brainstem. With the

pons and medulla, the midbrain is involved in many functions,

including regulation of heart rate, respiration, pain perception,

and movement.

MITOCHONDRIA Small cylindrical organelles inside cells that provide

energy for the cell by converting sugar and oxygen into special

energy molecules, called adenosine triphosphate (ATP).

MONOAMINE OXIDASE (MAO) The brain and liver enzyme

that normally breaks down the catecholamines norepinephrine,

dopamine, and epinephrine, as well as other monoamines such

as serotonin.

MOTOR NEURON A neuron that carries information from the

central nervous system to muscle.

MYASTHENIA GRAV IS A disease in which acetylcholine receptors

on muscle cells are destroyed so that muscles can no longer respond

to the acetylcholine signal to contract. Symptoms include muscular

weakness and progressively more common bouts of fatigue. The

disease’s cause is unknown but is more common in females than in

males; it usually strikes between the ages of 20 and 50.

MYELIN Compact fatty material that surrounds and insulates the

axons of some neurons.

NMDA RECEPTORS N-methyl-d-aspartate (NMDA) receptors,

one of three major classes of glutamate receptors, which have been

implicated in activities ranging from learning and memory to development

and specification of nerve contacts in a developing animal.

NECROSIS Cell death due to external factors, such as lack of

oxygen or physical damage, that disrupt the normal biochemical

processes in the cell.

NERVE GROWTH FACTOR A substance whose role is to guide

neuronal growth during embryonic development, especially in the

peripheral nervous system. Nerve growth factor also probably helps

sustain neurons in the adult.

NEURON A nerve cell specialized for the transmission of information

and characterized by long, fibrous projections called axons and

shorter, branchlike projections called dendrites.

NEUROPLASTICITY A general term used to describe the adaptive

changes in the structure or function of nerve cells or groups of

nerve cells in response to injuries to the nervous system or alterations

in patterns of their use and disuse.

NEUROTRANSMITTER A chemical released by neurons at a synapse

for the purpose of relaying information to other neurons

via receptors.

NOCICEPTORS In animals, nerve endings that signal the sensation

of pain. In humans, they are called pain receptors.

NOREPINEPHRINE A catecholamine neurotransmitter, produced

both in the brain and in the peripheral nervous system. Norepinephrine

is involved in arousal and in regulation of sleep, mood,

and blood pressure.

OCCIPITAL LOBE One of the four subdivisions of the cerebral cortex.

The occipital lobe plays a role in processing visual information.

OLFACTORY BULB A round, knoblike structure of the brain

responsible for processing the sense of smell. Specialized olfactory

receptor cells are located in a small patch of mucous membrane lining

the roof of the nose. Axons of these sensory cells pass through

perforations in the overlying bone and enter two elongated olfactory

bulbs lying on top of the bone.

ORGANELLES Small structures within a cell that maintain the cell

and do the cell’s work.

PA RASYMPA THETIC NERVOUS SYSTEM A branch of the autonomic

nervous system concerned with the conservation of the

body’s energy and resources during relaxed states.

PA RIETAL LOBE One of the four subdivisions of the cerebral cortex.

The parietal lobe plays a role in sensory processes, attention, and


PA RKINSON’S DISEASE A movement disorder caused by death of

dopamine neurons in the substantia nigra, located in the midbrain.

Symptoms include tremor, shuffling gait, and general reduction in


PEPTIDES Chains of amino acids that can function as neurotransmitters

or hormones.

PERIPHERAL NERVOUS SYSTEM A division of the nervous system

consisting of all nerves that are not part of the brain or spinal cord.

PHOSPHORYLATION Transfer of a phosphate molecule from adenosine

triphosphate (ATP) to a protein (ion channel, neurotransmitter

receptor, or other regulatory protein), resulting in activation

or inactivation of the protein. Phosphorylation is believed to be

a necessary step in allowing some neurotransmitters to act and is

often the result of second-messenger activity.

PHOTORECEPTOR A nerve ending, cell, or group of cells specialized

to sense or receive light.

PITUITARY GLAND An endocrine organ closely linked with the

hypothalamus. In humans, the pituitary gland is composed of two

lobes and secretes several different hormones that regulate the

activity of other endocrine organs throughout the body.

PONS A part of the hindbrain that, with other brain structures,

controls respiration and regulates heart rhythms. The pons is a major

route by which the forebrain sends information to and receives

information from the spinal cord and peripheral nervous system.
PSYCHOSIS A severe symptom of mental disorders characterized

by an inability to perceive reality. Psychosis can occur in many

conditions, including schizophrenia, mania, depression, and druginduced


RECEPTOR CELL A specialized sensory cell, designed to pick up and

transmit sensory information.

RECEPTOR MOLECULE A specific protein on the surface of or

inside a cell with a characteristic chemical and physical structure.

Many neurotransmitters and hormones exert their effects by binding

to receptors on cells.

RETINA A multilayered sensory tissue that lines the back of the eye

and contains the receptor cells to detect light.

REUPTAKE A process by which released neurotransmitters are

absorbed for later reuse.

ROD A sensory neuron located in the periphery of the retina. The

rod is sensitive to light of low intensity and is specialized for nighttime


SCHIZOPHRENIA A chronic mental disorder characterized by

psychosis (e.g., hallucinations and delusions), flattened emotions,

and impaired cognitive function.

SECOND MESSENGERS Substances that trigger communications

among different parts of a neuron. These chemicals play a role in

the manufacture and release of neurotransmitters, intracellular

movements, carbohydrate metabolism, and processes of growth and

development. The messengers’ direct effects on the genetic material

of cells may lead to long-term alterations of behavior, such as

memory and drug addiction.

SEROTONIN A monoamine neurotransmitter believed to play

many roles, including but not limited to temperature regulation,

sensory perception, and the onset of sleep. Neurons using serotonin

as a transmitter are found in the brain and gut. Several antidepressant

drugs are targeted to brain serotonin systems.

SHORT-TERM MEMORY A phase of memory in which a limited

amount of information may be held for several seconds or minutes.

STEM CELL Unspecialized cells that renew themselves for long

periods through cell division.

STIMULUS An environmental event capable of being detected by

sensory receptors.

STROKE A block in the brain’s blood supply. A stroke can be

caused by the rupture of a blood vessel, a clot, or pressure on a blood

vessel (as by a tumor). Without oxygen, neurons in the affected

area die and the part of the body controlled by those cells cannot

function. A stroke can result in loss of consciousness and death.

SYMPA THETIC NERVOUS SYSTEM A branch of the autonomic

nervous system responsible for mobilizing the body’s energy and

resources during times of stress and arousal.

SYNAPSE A physical gap between two neurons that functions as

the site of information transfer from one neuron to another.

TASTE BUD A sensory organ found on the tongue.

TEMPORAL LOBE One of the four major subdivisions of each

hemisphere of the cerebral cortex. The temporal lobe functions in

auditory perception, speech, and complex visual perceptions.

THALAMUS A structure consisting of two egg-shaped masses of

nerve tissue, each about the size of a walnut, deep within the brain.

The key relay station for sensory information flowing into the

brain, the thalamus filters out information of particular importance

from the mass of signals entering the brain.

VENTRICLES Comparatively large spaces filled with cerebrospinal

fluid. Of the four ventricles, three are located in the forebrain and

one in the brainstem. The lateral ventricles, the two largest, are

symmetrically placed above the brainstem, one in each hemisphere.

WERNICKE’S AREA A brain region responsible for the comprehension

of language and the production of meaningful speech.

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.