Terms and Definitions

• Acetylcholine


  A critical neurotransmitter that controls functions such as memory, attention, sleep, heart rate, and muscular activity.
• 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.
• Addiction


  Loss of control over drug intake or compulsive seeking and taking of drugs, despite adverse consequences.
• Adenosine


  A neurochemical that inhibits wakefulness, serving the purpose of slowing down cellular activity and diminishing arousal. Adenosine levels decrease during sleep.
• Adrenal Gland

  An endocrine organ that secretes hormones. The outer layer (adrenal cortex) secretes cortisol. The inner portion (adrenal medulla) secretes epinephrine and norepinephrine alongside activation of the sympathetic nervous system in the “fight or flight” response.
• Alzheimer’s Disease (AD)


  A major cause of dementia, this neurodegenerative disorder is characterized by neuron death in the hippocampus, cerebral cortex, and other regions. Early symptoms include forgetfulness, disorientation, and difficulty concentrating. In the final stages, individuals are incapable of self-care and may be bedridden.
• Amnesia


  A memory impairment usually caused by brain damage or disease, or by drugs such as some anesthetics. People with amnesia may be unable to recall events from the past, form new memories, or both.
• 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.
• Amyotrophic Lateral Sclerosis (ALS)


  Commonly known as Lou Gehrig’s disease, ALS causes motor neurons in the brain and spinal cord to disintegrate, resulting in loss of control of voluntary muscle movements such as walking.
• Analgesic


  A drug that relieves pain without causing a loss of consciousness.
• Anxiety


  A state of heightened arousal characterized by intense worry.
• 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 an animal.
• Arousal 


  A physiological state involving changes in the body and brain that motivate behavior and enable response to stimuli.
• Astrocyte


  A star-shaped glial cell in the central nervous system that nourishes neurons; regulates the formation, maintenance, and pruning of synapses; and contributes to the blood-brain barrier.
• Attention


  A state of arousal in which the brain’s sensory processing is directed at a limited number of stimuli. Voluntary (endogenous) attention is a conscious decision to focus on a particular stimulus. Involuntary (exogenous) attention is an unplanned focus on a change in the environment.
• Attention Deficit Hyperactivity Disorder (ADHD) 


  A condition characterized by excessively inattentive, hyperactive, or impulsive behaviors.
• Auditory Nerve


  A branch of the vestibulocochlear nerve that transmits auditory information from the cochlea of the ear to the brain.
• Autism Spectrum Disorder (ASD)


  A set of conditions characterized, in part, by impaired social communication and interaction, and narrow, obsessive interests or repetitive behaviors.
• 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 fiber-like extension of a neuron by which it sends information to target cells
• Axon Terminal


  The ends of axons where neurotransmitters are released to target cells.
• Basal Ganglia 


  A group of interconnected structures located deep in the brain that play an important role in voluntary movement, motor skill learning, and habits. These structures include the caudate nucleus, putamen, nucleus accumbens, globus pallidus, and substantia nigra.
• Benzodiazepines 


  A class of drugs that enhance activity of the brain’s primary inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), to produce sedative and anti-anxiety effects. Benzodiazepines are often prescribed to treat anxiety disorders and insomnia.
• Blood-Brain Barrier 


  A protective membrane composed of tightly packed endothelial cells lining the brain’s capillaries and highly specialized astrocytes, which controls the passage of certain molecules into and out of the brain.
• Brain Waves 


  Oscillating patterns of brain activity that can be detected and recorded using electroencephalography (EEG).
• Brain-Derived Neurotrophic Factor (BDNF)


  A neurotrophic peptide that supports the growth and survival of neurons.
• Brainstem 


  The major route by which the forebrain sends information to and receives information from the spinal cord and peripheral nerves. The brainstem includes the midbrain, pons, and medulla, and it controls, among other things, respiration and the regulation of heart rhythms
• Broca’s Area 


  A region of the frontal lobe — usually the left hemisphere — that governs speech production.
• Cell Body


  Also called the soma, the part of a neuron that contains the nucleus (with DNA) and the organelles, but not the projections such as the axon or dendrites.
• Central Nervous System


  The brain and spinal cord.
• Cerebellum 


  A large structure located at the roof of the hindbrain that helps to 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 wrinkled, outermost layer of the cerebrum consisting primarily of neuron cell bodies.
• Cerebrum 


  The largest part of the human brain associated with higher order functioning, such as thinking, perceiving, planning, and understanding language, as well as the control of voluntary behavior.
• Circadian Rhythms


  A cycle of behavior or physiological change lasting approximately 24 hours.
• Cochlea


  A snail-shaped, fluid-filled organ of the inner ear responsible for converting sound into electrical potentials to produce an auditory sensation.
• Cognitive Behavioral Therapy


  A form of counseling used to identify and change negative thought patterns that can contribute to anxiety and mood disorders
• Computational Neuroscience


  A field of neuroscience research that uses computer programs and algorithms to analyze information about the brain, and develops mathematical models to explain brain function.
• Cones


  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.