Acetylcholine
A neurotransmitter in the brain and body that is formed by the combination of acetic acid and choline.
Acetylcholinesterase
An enzyme present in nervous tissue and at the neuromuscular junction that catalyzes hydrolysis of acetylcholine to choline and acetic acid.
Action potential
A brief change in the electrical charge across the membrane of a nerve that travels away from the cell body, along the axon, until it reaches the axon terminal, where it induces the release of a neurotransmitter.
Alzheimer’s disease
An irreversible and progressive brain disorder that slowly impairs memory and thinking skills, and eventually the ability to perform simple tasks.
Amnesia
An inability to remember past events or impairment in the ability to form new long-term memories.
Amygdala
A structure located in the ventral region of the temporal lobe and considered to be a part of the limbic system. It is involved in the initiation of emotions, principally the production of a fear response.
Analgesic
A drug that dulls the sensation of pain. It differs from an anesthetic agent in that it relieves pain without loss of consciousness.
Anticholinergic
A drug that blocks, inhibits, or antagonizes the actions of acetylcholine or other cholinergic receptor agonists. Because the predominant effects of the parasympathetic nervous system are mediated by acetylcholine, the term “anticholinergic effects” often is used to imply an inhibitory action in the parasympathetic nervous system.
Anxiolytic
A drug that reduces anxiety.
Astrocytes
One of the three major classes of glial cells found in the central nervous system; important in providing nutrients to the neurons and removing metabolic and neurotransmitter byproducts.
Autonomic nervous system
Subdivided principally into the sympathetic and parasympathetic efferent systems. It controls the function of visceral organs and allows the expression of the physical components of emotion.
Axon.
The straight, relatively unbranched process of a nerve cell that carries the action potential to the terminal for release of a neurotransmitter.
B.C.E.
Before the common era.
Bilateral
On both sides of the brain.
Blood–brain barrier
Functional barrier produced by glia wrapped around blood vessels preventing access for many blood-borne molecules to the brain. The barrier consists mostly of the fatty membranes of the astrocytes and the existence of tight junctions between the vascular endothelial cells.
Broca’s area
An area in the left frontal lobe specialized for the production of speech.
Central nervous system
The brain and spinal cord.
Cerebellum
Means “little brain” in Latin. It is involved in learning, the coordination and production of speech, the organization of muscle movement, coordination of fine motor movement, and balance; it is the center of a feedback loop involving motor and sensory information.
Cerebral cortex
The thin outer layer of the cerebral hemisphere, which contains neurons that are organized in six horizontal layers as vertical columns. It appears as ridges (gyri) and narrow folds (sulci) in order to maximize the number of neurons and number of columns within the confined space of the skull. It is 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.
Cerebral hemispheres
The two halves of the brain. The left hemisphere is specialized for initiating speech, language, writing, and calculation. The right hemisphere is specialized for initiating spatial abilities, face recognition in vision, and some aspects of music perception and production.
Dementia
Loss of higher intellectual function. This condition may be progressive due to some underlying disease process or may be drug induced.
Dendrite
The parts of the neuron that receive information from other neurons. These structures contain receptors and are able to form synapses with incoming neurons.
Dura mater
The thick external covering of the brain and spinal cord; one of the three components of the meninges, the other two being the pia mater and arachnoid.
Endocannabinoids
The endogenous lipid-soluble chemicals anandamide and 2-AG that bind to the brain’s marijuana receptors. Endocannabinoids are unlike most of the brain’s transmitters because they are not stored in synaptic vesicles but are synthesized by neurons upon demand.
Endorphins
Protein neurotransmitters that mimic the action of morphine.
Frontal lobe
One of the four lobes of the brain; it includes all of the cortex that lies in the front half of the brain.
GABA
Gamma-amino butyric acid is a neurotransmitter with major inhibitory function in the brain and body. Its primary function is to turn off the activity of other neurons.
Gastrointestinal system
Pertaining to the stomach and intestines.
Glutamate
A neurotransmitter with major excitatory function in the brain and body. Its primary function is to increase the activity of other neurons.
Gray matter
The parts of the nervous system that contain neuronal cell bodies and very little myelin (known as white matter). In fresh dissection, these regions appear grayish.
Gyrus
A ridge or fold between two clefts (sulcus) on the cerebral cortex. The gyri and sulci create the folded appearance of the brain in humans and other mammals.
Hallucination
An altered sensory experience in a conscious and awake state that can be initiated by the brain or due to the presence of an external stimulus, such as a drug. Hallucinations are most often visual and/or auditory, but also can involve the sense of taste, touch, and pain.
Ipsilateral
On the same side of the body.
Hypothalamus
A brain region located at the bottom center of the brain. It is responsible for controlling feeding behaviors, body temperature, thirst, and hormone release from the pituitary gland.
Limbic system
A circuit of brain structures that plays a role in the control and production of emotional behavior.
Lipid solubility
The property of a chemical to dissolve in fat. Due to the fatty components of the blood–brain barrier, lipid-soluble chemicals will enter the brain more easily than chemicals that are not lipid soluble.
Long-term potentiation (LTP)
An increase in size of a synaptic electrical potential lasting one hour or more. LTP is considered an artificially produced electrophysiological representation of the actual neural processes that underlie a memory.
Mammal
An animal the embryos of which develop in a uterus and the young of which begin to suckle at birth (technically, a member of the class Mammalia).
Microglial
A type of glia that plays a critical role in the immune responses of the brain.
Mitochondria
A small membrane-bound organelle found in large numbers in most cells of the body, in which the biochemical processes of respiration and energy production occur.
Myelin
A sheath of fatty material that surrounds most axons. It acts as an insulator to enhance electrical conduction of action potentials.
Myelination
Process by which glial cells wrap axons to form myelin that increase axonal conduction velocity.
Narcolepsy
A rare disabling hypersomnia disorder that may include cataplexy, sleep paralysis, hypnagogic hallucinations, and sleep-onset rapid eye movement (REM) periods, but also disrupted nighttime sleep by nocturnal awakenings, and REM sleep behavior disorder (RBD).
Neuron
The basic functional unit of the nervous system, also called a nerve cell. It is specialized for the transmission of information and characterized by long fibrous projections called axons, as well as shorter, branch-like projections called dendrites.
Non-rapid eye movement (non-REM) sleep
Collectively, those phases of sleep characterized by the absence of rapid eye movements.
Nystagmus
An involuntary, usually lateral, back-and-forth rhythmic eye movement.
Occipital lobe
One of the four lobes of the brain. It is responsible for vision and visual object and face recognition. This lobe is located at the most posterior part of the brain.
Orexin
A protein neurotransmitter that controls arousal and feeding behaviors.
Parasympathetic nervous system
Part of the autonomic nervous system. This system is involved with maintenance of bodily activities and conservation of energy.
Parietal lobe
One of the four lobes of the brain. It is responsible for processing higher sensory and language functions. This lobe is located on the top of the brain.
Parkinson’s disease
A degenerative disease that results in a tremor at rest, usually involving the hands and feet at first, along with a general slowness in movement.
Pia mater
The innermost layer of the membranes surrounding and protecting the brain that closely follows the bumps and wrinkles of the brain’s surface.
Placebo
A medicine or preparation with no pharmacologic activity, which is effective only by virtue of the power of suggestion associated with its administration.
Poikilotherm
An organism whose internal temperature varies in relation to the temperature of the environment. It is the opposite of a homoeotherm, an organism that maintains thermal homeostasis.
Prefrontal cortex
The very anterior-most part of the brain, which controls planning and thought.
Presynaptic
The site from which the neurotransmitter is released, usually at the end of an axon.
Pseudoscience
A claim, belief, or practice that is incorrectly presented as scientific but does not adhere to a valid scientific method, cannot be reliably tested, or otherwise lacks scientific status.
REM atonia
A sleep disorder characterized by the loss of normal voluntary muscle tone during REM dream sleep.
Receptor
A protein floating on the surface of a neuron. Usually these proteins are the point of interaction between two neurons or between a drug and a neuron.
Reuptake
When some neurotransmitters are released into the synaptic cleft, a fraction of the released molecules is recovered by transport back into the axon terminal, where it may be reused or degraded. Some drugs (called selective reuptake inhibitors) can interfere with this process.
Serotonin
A neurotransmitter derived from the dietary amino acid tryptophan.
Sulcus (plural = sulci)
The valleys or spaces between the folds or gyri of the brain.
Sympathetic nervous system
The sympathetic nervous system is part of the autonomic nervous system. In general, this is a system that is involved with activation of bodily activities and mobilization of energy-consuming activities (increase in heart rate, respiration). This system has been characterized as the “flight-or-fight” system.
Synapse
The place where one neuron connects to another neuron. The synapse includes the nerve terminal of the first neuron, the spot on the second neuron with receptors, and the space between them.
Synaptic vesicles
Membrane spheres that contain neurotransmitter molecules that are stored near the presynaptic membrane at the synapse.
Synesthesia
A phenomenon in which stimulation of one sensory pathway leads to automatic, involuntary experiences in a second sensory pathway. The experience varies in intensity and people vary in awareness of their synesthetic perceptions.
Temporal lobe
One of the four lobes of the brain. It is responsible for processing hearing, olfaction, object recognition, language, speech, learning, and memory. It is located on lateral sides of each brain hemisphere near the ears.
Wernicke’s area
Region of cortex in the left temporal lobe that helps mediate language comprehension.
White matter
Those parts of the brain and nervous system that primarily contain axons wrapped with myelin.
