Glossary of Neuroscience Terms

Glossary A-to-Z: Click on the letters to browse the content alphabetically.

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abdomen
the hindmost of an insect's three major body sections; the center for digestion and reproduction (M. sexta Wax Model)

abdominal
relating to or involving the abdomen (M. sexta Wax Model)

action potential
an electrical signal that travels along the axon, away from the cell body to the axon terminal where it triggers the release of neurotransmitters (Virtual Neurons, Connect the Neurons)

action potential amplitude
The maximum amplitude of an action potential is a constant value, greater than 0mV. The total amplitude of an action potential is the displacement from the resting potential to the maximum amplitude, usually 70mV or more.

afferent
incoming information or neuronal connection; coming into or towards the central nervous system

amygdala
part of the brain involved in processing the memory of emotional reactions, notably fear and anger (Sheep Brain Dissection)

anterior
toward the front or the head, see also rostral (Sheep Brain Dissection)

arachnoid mater
middle layer of the 3 membranes surrounding and protecting the brain. The space between the arachnoid and pia mater contains many blood vessels that supply the brain.

association cortex
parts of cortex putting together and interpreting sensory information (Motor Learning)

audition
the sense of hearing; the ability to detect information from sound waves

axon
the neuronal process that sends the signal or message away from the cell body toward target cells or neurons (Connect the Neurons, Close-up of the Nervous System, Bead Neuron)

axon terminal
the very end part of an axon that makes a synaptic contact with another cell; the point where neurotransmitters are released (Connect the Neurons, Close-up of the Nervous System)

balance
the sense of body movement with respect to gravity

bilayer
two layers of lipid molecules with their water-liking sides facing outward and their water-hating sides facing each other; lipid bilayers form plasma membranes of cells and membranes of other organelles.

blood volume
the total amount of blood in a body

brainstem
the part of the central nervous system connecting the brain to the spinal cord. The brainstem contains pathways sending information to and receiving information from the spinal cord and peripheral nerves. It also contains neurons that control respiration and regulation of heart rhythms. (Sheep Brain Dissection)

carbohydrate
complex organic molecules composed of carbon, hydrogen, and oxygen that store energy and act as structural components of cells

caudal
towards the tail; the tail end of the nervous system

cell body
the bulbous part of the neuron, also called the soma, that contains the nucleus. Dendrites and axons are processes off of the cell body. (Bead Neuron)

central nervous system
the brain and spinal cord

cerebellum
the highly folded part of the central nervous system above or dorsal to the brainstem that helps control movement, balance, and muscle coordination (Sheep Brain Dissection, Close-up of the Nervous System, Mirror Image)

cerebral cortex
the largest and most complex part of the mammalian central nervous system; appears as tightly packed fat ridges (gyri) and narrow folds (sulci); responsible for all forms of conscious experience, including perception, emotion, thought, and planning. Cortex means bark in Greek; the bark of the cork tree looks a lot like the cerebral cortex. (Sheep Brain Dissection, Close-up of the Nervous System, Memory Items)

cerebral hemispheres
the two halves of the cerebral cortex. The left hemisphere is specialized for initiating speech, language, writing, and calculations. The right hemisphere is specialized for initiating spatial abilities, face recognition in vision, and some aspects of music perception and production

cerebrum
see cerebral cortex (Sheep Brain Dissection, Close-up of the Nervous System)

chemotaxis
when a growth cone follows chemical signals (chemo-) to move toward (-taxis) a desired target (Neuropathfinding, C. elegans + Alcohol, Chemotaxis using C. elegans)

circuit
sets of neurons connected in a pathway that perform a function; a neuronal circuit carries information from one point in the body or nervous system to another. A neuronal circuit is not like an electrical circuit where current must flow in a complete circle. A neuronal circuit uses electrical and chemical energy to carry information along a path. A neuronal circuit can have feedback and feed forward loops within it.

CNS
central nervous system consisting of the brain and spinal cord

corpus callosum
a large bundle of nerve fibers (myelinated axons) that link the right and left hemispheres of the brain; enables the two hemispheres to share information (Sheep Brain Dissection)

cranial nerve
twelve pairs of nerves that arise from each side of the brain stem numbered I to XII from anterior to posterior

declarative memory
see memory, declarative (Mirror Image, Your Incredible Memory)

dendrite
tree-like extension of the neuronal cell body; receives chemical neurotransmitter signals or messages from other neurons (Bead Neuron)

depolarize
movement of membrane potential to a higher (more positive) value

disease of learning
a way to describe addiction (Dendritic Spines Lab, What's the Deal? Addiction Card Game)

distal
away from, far end

dopamine
a neurotransmitter used in the brain's reward circuit which signals a positive benefit to an action nor met expectation (Dendritic Spines Lab)

dorsal
toward the back of the body or top of the head (Sheep Brain Dissection)

dorsal horn
dorsal part of the spinal cord gray matter where axons from sensory neurons enter and make their first synapses (Close-up of the Nervous System)

dorsal root ganglion (DRG) neurons
sensory neurons for the skin and muscle; cell bodies of these sensory neurons are grouped in a structure called a ganglion just outside the spinal cord on the dorsal side. Thus they are called Dorsal Root Ganglion Neurons. They have no dendrites. Their axons branch immediately. One branch goes to the periphery (skin or muscle); the other into the spinal cord. Sensory information from the periphery travels from one end of the axon to the other synapsing in the dorsal horn of the spinal cord.

dura mater
tough, leathery outermost layer of the membranes surrounding and protecting the brain and spinal cord; lines the inside of the skull and drapes loosely around the spinal cord. Dura mater is Latin for tough mother. (Sheep Brain Dissection)

electrolytes
charged ions like sodium, potassium, chloride, and bicarbonate

endocrine system
system of glands and groups of cells that secrete hormones to control internal body states

efferent
outgoing information or neuronal connection; going away from or out of the central nervous system

episodic memory
see memory, episodic (Your Incredible Memory)

EPSP
see excitatory post-synaptic potential

excitatory interneuron
an interneuron whose neurotransmitter produces excitation (depolarization) in target cells, helping the target cells to reach threshold

excitatory neuron
see neuron, excitatory (Virtual Neurons)

excitatory post-synaptic potential
short-lived movement of membrane potential to a higher value when neurotransmitter binds to receptors on dendrites; temporary depolarization of post-synaptic membrane potential caused by the flow of positively charged ions into the post-synaptic cell as a result of opening of ligand-gated channels. makes a post-synaptic neuron more likely to generate an action potential; opposite of IPSP definition from Wikipedia

ethics
the principles of right and wrong behavior governing a group of people (Whose Choice is it Anyway?)

experimental control
the experimental condition which receives no treatments (negative control) or receives treatments already known to cause the desired effect (positive control) (Chemotaxis using C. elegans)

extracellular
outside the cell

feedback
when information from the end is also used to modify the process that produced it; in a feedback loop, information moves backwards to add into an earlier part of the pathway.

feedback loop
in a feedback loop, information moves backwards to add into an earlier part of the pathway.

feed-forward network
occurs when a signal from one point in a neural pathway is transmitted in a forward direction and adds information to the circuit

firing rate
the number of action potentials generated per second

frequency
the rate of a repeated event; usually measured in # of events per second = Hertz = Hz. Frequency = 1 / period

frontal cortex
any part of the frontal lobe; involved in decision making, evaluating, and directing behaviors (Whose Choice Is It Anyway?)

frontal lobe
front region of the cerebrum; the part of the cortex responsible for attention, decision making, abstract thinking, problem solving, emotion, intellect, muscle movements, smell, and personality; motor cortex (Sheep Brain Dissection, Mirror Image, Motor Learning)

ganglion (plural = ganglia)
a group or collection of neuronal cell bodies (Close-up of the Nervous System, M. sexta Wax Model)

gap junction
ion channels in adjoining cells that align to form electrical synapses; gap junctions are turned on and off by calcium and pH.

glands
specialized groups of cells in the endocrine system that secrete hormones, directly into the blood rather than through a duct

glutamate receptor
nonselective cation channels which allows the flow of K+, Na+ and sometimes Ca2+ in response to glutamate binding

graded synaptic potential
small change in membrane potential of the post-synaptic dendrite caused by transmitter released from the pre-synaptic nerve terminal; synaptic potentials are much smaller than action potentials.

gray matter
areas of the brain made up of neuronal cell bodies, dendrites and synapses; without a lot of myelin, these areas appear grayer in freshly dissected brain tissue.

growth cone
the tip of the growing axon that senses and uses chemical signals to find its targets (Neuropathfinding)

gyrus (plural = gyri)
ridges or bumps of folded cerebral cortex

head
the frontmost part of an animal that usually contains the brain, eyes, ears, nose, and mouth

hippocampus
the oldest part of cerebral cortex responsible for spatial localization, formation of declarative memory, and transfer of short-term to long-term memories (Sheep Brain Dissection, Memory Items)

homeostasis
self-regulating process by which a system remains stable by adjusting to changing conditions (Dendritic Spines Lab, Makes Me Sweat, Virtual Neurons)

hyperpolarize
movement of membrane potential to a lower (more negative) value

hypothalamus
part of the brain that processes appetite, thirst, hormone regulation, control of internal body functions, sexual functions, and diurnal rhythms; the hypothalamus is a medial structure below (more ventral than) the thalamus.

inertia
the tendency of a body to remain in a state of rest or uniform motion unless acted upon by an external force (Balance: The Ears Have It)

inhibitory neuron
see neuron, inhibitory (Virtual Neurons)

inhibitory post-synaptic potential
short-lived movement of membrane potential to a lower value when neurotransmitter binds to receptors on dendrites; temporary hyperpolarization of post-synaptic membrane potential caused by the flow of positively charged ions out of the post-synaptic cell (or negatively charged ions moving in) as a result of opening of ligand-gated channels. makes a post-synaptic neuron less likely to generate an action potential; opposite of EPSP definition from Wikipedia

interneuron
a neuron that carries information between sensory neurons and motor neurons; most meurons in the CNS are interneurons; some have special names like projection neurons or Pyramidal cells. (Virtual Neurons)

intracellular
inside the cell

ion channel
a membrane-spanning protein that forms a pore or hole through the plasma membrane; when the ion channel is open, ions move between the inside and outside of the cell. Most ion channels are opened or closed by energy, for example, from a binding reaction, voltage, temperature, or light.

ionotropic
receptor that also is an ion channel

IPSP
see inhibitory post-synaptic potential

labyrinth
an organ in the middle ear that holds the 3 semicircular canals which come together in the vestibule, close to the cochlea (Balance: The Ears Have It)

latency
a property of neurons specifying the time (in milliseconds) between arrival of a stimulus and production of the response; the time between a stimulus and its response

lateral
toward the left or right sides of the body, away from the middle; opposite of medial (Sheep Brain Dissection)

lobe
large division of the cerebral cortex

long-term memory
memories that are stored in a variety of places in the brain over long periods of time (Recency and Primacy Effects)

lung
the organ producing breathing

medial
toward the middle of the body; opposite of lateral (Sheep Brain Dissection)

membrane potential
electrical difference between the inside and outside of a neuron or muscle cell

memory, declarative
type of memory used when recalling (or declaring) facts or experiences, as opposed to skills. Both semantic and episodic memories are declarative memories and can easily be forgotten. (Mirror Image, Your Incredible Memory)

memory, episodic
type of declarative memory used when one talks about events in one’s life (includes time, place and emotions) (Your Incredible Memory)

memory, procedural
type of memory used in performing skills, learned behaviors, or procedures; remembering how to do something like tie a shoelace. Procedural memories are easy to do but difficult to explain to others. For example, it is easy to demonstrate how to ride a bike but it is not easy to describe how to do it. Procedural memories are less likely to be forgotten. (Mirror Image, Your Incredible Memory)

memory, semantic
type of declarative memory used when talking about facts and concepts (Your Incredible Memory)

meninges
three membranes (the dura mater, arachnoid mater, and pia mater) that cover and protect the brain and spinal cord against shocks, knocks, and vibrations; blood vessels run between the arachnoid and pia mater before entering into the cortex. (Sheep Brain Dissection)

merkels discs
small structures in the skin that provide touch information to sensory nerves

metabotropic
receptor that activates a series of intracellular biochemical reactions

metamorphosis
development or transformation of an organism; involves significant changes in physical form (e.g. growth and differentiation) (M. sexta Wax Model)

mnemonic
a device or way (a rhyme, a word) to aid in remembering something; HOMES to remember the 5 Great Lakes (Huron Ontario Michigan Erie Superior) (Memory Items)

motor cortex
part of frontal cortex that sends messages to the spinal cord for movement control; see frontal lobe (Mirror Image, Motor Learning)

motor learning
is the process of improving the smoothness and accuracy of movements through practice. During motor learning (and other learning), synapses in neural pathways in the brain are strengthened so that the actions (or thought) progress smoothly with less conscious direction.

motor neuron
see neuron, motor (Virtual Neurons)

muscle fiber
muscle cells fused into a long multinucleated cell which can contract and exert force; motorneurons innervate muscle fibers, not individual muscle cells. Many muscle fibers running in parallel form a muscle.

muscle spindle
senses the stretch of a muscle and sends that information back to the spinal cord and cerebellum to help control muscle length

myelin
compact fatty material that surrounds axons of some neurons; acts as an insulator to enhance electrical conduction of action potentials (Sheep Brain Dissection, Close-up of the Nervous System)

myelinate
to form myelin around an axon

negative feedback
information feeding back which is subtracted from the process thereby slowing the process down

nerve terminal
the end region of an axon; usually a site of synaptic contact with another cell

nervous system
a vast network of cells that carry information to and from all parts of the body (M. sexta Wax Model)

neural circuit
the set of neurons that are connected in sequence to produce a sensation, behavior, or function; neural pathway or network; see circuit (Bead Neuron)

neural pathway
set of connected neurons that are regularly activated in sequence to produce a specific function; neural circuit or network

neuroethics
questions about ethics raised from neuroscience experiments (Whose Choice is it Anyway?)

neuromarketing
a new branch of neuroscience concerned with determining public preferences and marketing strategies based upon fMRI brain scans (Whose Choice is it Anyway?)

neuromuscular junction
a specialized synapse onto a muscle; the place where the neuron connects to the muscle (Virtual Neurons, Connect the Neurons)

neuron
a cell that is specialized for the transmission of information and characterized by long fibrous projections called axons, and shorter, branch-like projections called dendrites; the basic functional unit of the nervous system; also called a nerve cell (Virtual Neurons, Connect the Neurons, Close-up of the Nervous System, Bead Neuron)

neuron, excitatory
a neuron whose neurotransmitter excites, stimulates, or depolarizes (causes the cell membrane to become less negative) another neuron, increasing the probability that the target neuron will fire an action potential; in other words, an excitatory neuron sends a message that may cause another neuron to fire an action potential; excites the next neuron (Virtual Neurons, Connect the Neurons)

inhibitory neuron
a neuron whose neurotransmitter produces inhibition (hyperpolarization) in target cells, making it harder for the target cell to reach threshold

neuron, motor
a neuron that carries information away from the central nervous system to muscles; a motor neuron sends messages to move muscles (Virtual Neurons)

neuron, post-synaptic
the neuron whose dendrites receive the neurotransmitter (Connect the Neurons)

neuron, pre-synaptic
the neuron that releases the neurotransmitter (Connect the Neurons)

neuron, sensory
a neuron that picks up information from the body's sensory receptors in the skin, muscle, joints, tongue, ear, nose, and eyes and carries it toward the central nervous system; sensory neurons detect environmental information necessary for the body to survive, e.g. touch, pain, temperature, light, sound, taste, smell, balance, and information about muscles and joints. (Virtual Neurons)

neuronal circuit
see circuit

neuronal network
neuronal circuit; see circuit

neurotransmitter
a chemical, released by nerve terminals at a synapse, that crosses the synapse carrying information from the nerve terminal (pre-synaptic cell) to the dendrite (post-synaptic cell). Neurotransmitters, which are stored in synaptic vesicles in the pre-synaptic cell, bind to receptors on dendrites of neighboring neurons. Neurotransmitters relay information across the space between one neuron's nerve terminal and another neuron's dendrites. (Connect the Neurons)

nucleotide
See nucleic acid.

nystagmus
an involuntary rhythmic eye movement that occurs when a person is spun around and then suddenly stops (Balance: The Ears Have It)

occipital lobe
the part of the cortex responsible for vision and visual object and face recognition; the most caudal or posterior part of the cerebral cortex. (Sheep Brain Dissection, Mirror Image, Motor Learning)

olfactory bulb
anterior part of the brain concerned with the sense of smell (Sheep Brain Dissection)

optic chiasm
where the optic nerves from the left and right eyes come together. Some nerve fibers cross to the other side and some don't. All fibers continue in the optic track and synapse in the lateral geniculate nucleus of the thalamus. (Blind Spot)

optic nerve
nerve that connects the retina to the brain (Sheep Brain Dissection)

parietal lobe
region of the cerebrum located in the dorsal and medial region of the posterior cerebrum; processes higher sensory and language functions; association cortex (Sheep Brain Dissection, Motor Learning)

pathfinding
the process of the axons finding the right neuron or target to connect to (Neuropathfinding)

period
the time from the beginning of one event until the beginning of the next; usually measured in seconds; period = 1 / frequency.

peripheral
away from, outside

peripheral nervous system
nerves beyond the brain and spinal cord

pH
a measure of the hydrogen ion concentration in a liquid; pH = -log([H+])

pia mater
innermost layer of the membranes surrounding and protecting the brain that closely follows the bumps and wrinkles of the brain’s surface. The space between the arachnoid and pia mater contains many blood vessels that supply the brain

pioneer axon
the axon that happens to find its connection first and blazes a trail for other like axons to follow (Neuropathfinding)

pituitary gland
gland at the base of the brain; makes and releases growth, reproductive, and other hormones into the blood stream (Sheep Brain Dissection)

PNS
peripheral nervous system consisting of nerves beyond the brain and spinal cord

positive feedback
the information feeding back is added to the process thereby speeding up the process

posterior
towards the back of the head

post-synaptic neuron
see neuron, post-synaptic (Connect the Neurons)

potassium (K+)
element with a single positive charge found mostly inside neurons and muscles; K+ can move through some ion channels.

prefrontal cortex (PFC)
the very most anterior (rostral) part of the cortex which controls planning and thought

pre-synaptic neuron
see neuron, pre-synaptic (Connect the Neurons)

primacy effect
remembering the first information given, see also recency effect (Recency & Primacy Effect)

procedural memory
see memory, procedural (Mirror Image, Your Incredible Memory)

pruning
the process of shortening or reducing number of neuronal synapses, axons, or dendrites in response to use or growth signals (Neuropathfinding)

proprioception
the sense of oneself; where one feels the muscles, limbs, and body are with respect to one's surroundings. Sensory receptors in the muscles and joints send this information to the brain.

proximal
close to, nearest

purinergic receptor channels
a family of cation-permeable ligand-gated ion channels that open in response to the binding of extracellular purines, like adenosine 5'-triphosphate (ATP).

Purkinje cells
large neurons arranged in a single layer in the cerebellum that send messages to other areas of the brain that influence or refine movement (Close-up of the Nervous System)

reaction time
time it takes to react to a stimulus (Motor Learning)

recall
the act of retrieving memory (Your Incredible Memory)

recency effect
remembering the most recently received information, see also primacy effect (Recency & Primacy Effect)

receptor
a special molecule on a dendrite that tastes each specific neurotransmitter; neurotransmitter and receptor must fit together like a lock and key (Connect the Neurons)

recognition
the act of remembering words or situations that were previously learned or studied. It is also acknowledging and understanding something that is familiar. (Your Incredible Memory)

refractory period
a short time (a few msec) after an action potential when the neuron cannot produce another action potential

rod
photoreceptor cell in the retina of the eye that functions in low light; detects light and dark but not color

rostral
towards the nose or front of the nervous system; see also anterior (Sheep Brain Dissection)

semantic memory
see memory, semantic (Your Incredible Memory)

sensation
the ability to detect chemical or physical changes in the environment

sensory neuron
see neuron, sensory (Virtual Neurons)

short-term memory
an early stage in the processing of information in the brain; information only held for a few minutes. Some of this information will be lost or forgotten, while some will be processed into long-term memory. (Recency and Primacy Effects)

signal transduction pathways
sets of biochemical reactions inside cells that take information triggered by an external event like receptor activation and make that signal bigger or last longer; signal transduction pathways can cause other cellular events to happen including turning on or off genetic processes.

smell
the ability to detect specific chemicals floating in the air we breathe

soma
see cell body

somatosensation
the senses of touch, pressure, and pain as localized on the body surface

spinal cord
part of the central nervous system located inside the backbone containing cell bodies and bundles of nerve fibers; connects the brain to different sensory and motor parts of the body (Sheep Brain Dissection, Close-up of the Nervous System, Motor Learning)

sprouting
formation of new branches on axons or dendrites as they grow (Neuropathfinding)

sulcus (plural = sulci)
the valleys or spaces between the folds or gyri of the brain (Sheep Brain Dissection)

synapse
the place where one neuron connects to another. The synapse includes the nerve terminal of the first neuron, the place on the second neuron with receptors, and the space between them. The electrical signal in the axon of the first neuron triggers a chemical signal to be released into the gap that is tasted by receptors in the second neuron. (Connect the Neurons)

taste
the ability to detect specific chemicals in solutions and in food we put in our mouths

temporal lobe
the part of the cortex responsible for hearing, olfaction, object recognition, language, speech, learning, and memory; located in the ventral region of the lateral cerebrum near the temples and ears (Sheep Brain Dissection)

thalamus
interior part of the brain responsible for intermediate processing of motor and sensory functions and sleep

thoracic
relating to or involving the thorax (M. sexta Wax Model)

thorax
the middle section of an insect's body; the legs and wings attach to the thorax, making it the center for locomotion (M. sexta Wax Model)

threshold
the sum of incoming inputs needed to start an action potential; this value varies and is determined by the number of sodium channels in a neuron's cell body and the recent firing rate of that neuron. (Virtual Neurons, Close up of the Nervous System, Connect the Neurons)

tract
a bundle of axons in the central nervous system; a pathway

transmitter
short for neurotransmitter

variable
a factor or condition that is subject to change, especially one that is allowed to change in a scientific experiment to test a hypothesis. (Makes Me Sweat)

ventral
towards the front or stomach side of the body and head (Sheep Brain Dissection)

ventral horn
ventral part of spinal cord gray matter containing large motor neuron cell bodies (Close-up of the Nervous System)

ventricle
one of four fluid-filled cavities inside the brain

vertigo
a condition where a person feels as if s/he is spinning when s/he is not (Balance: The Ears Have It)

vestibular system
specialized sensory organs in the inner ear that sense head and body movements, the nerve that conveys this information into the brain, and the brain stem nuclei that process this information. The vestibular system is responsible for our sense of balance. (Balance: The Ears Have It)

vision
the sense of sight; the ability to detect information from wavelengths of light

visual cortex
see occipital lobe (Motor Learning)

white matter
areas of the brain made up of myelinated axons; the high lipid content of the myelin makes these areas appear whiter in freshly dissected brain tissue.