Involuntary (exogenous) attention is an unplanned focus on a change in the environment, such as a loud noise or sudden movement. Voluntary (endogenous) attention is a conscious decision to focus on a particular stimulus. AttentionĪ state of arousal in which the brain’s sensory processing is directed at a limited number of stimuli. AstrocyteĪ 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. ArousalĪ physiological state involving changes in the body and brain that motivate behavior and enable response to stimuli. Programmed cell death induced by specialized biochemical pathways, often serving a specific purpose in the development of an animal. Aphasiaĭisturbance in language comprehension or production, often as a result of a stroke. AnxietyĪ state of heightened arousal characterized by intense worry. AnalgesicĪ drug that relieves pain without causing a loss of consciousness. Amyotrophic Lateral Sclerosis (ALS)Ĭommonly 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. AmygdalaĪ 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. People with amnesia may be unable to recall events from the past, form new memories, or both. AmnesiaĪ memory impairment usually caused by brain damage or disease, or by drugs such as some anesthetics. In the final stages, individuals are incapable of self-care and may be bedridden. The earliest symptoms of the disease include forgetfulness disorientation as to time or place and difficulty with concentration, calculation, language, and judgment. Alzheimer's Disease (AD)Ī 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. The inner portion (adrenal medulla) secretes epinephrine and norepinephrine in concert with the activation of the sympathetic nervous system in the “fight or flight” response. The outer layer (adrenal cortex) secretes the stress hormone cortisol. Adrenal GlandĪn endocrine organ that secretes hormones. AdenosineĪ neurochemical that inhibits wakefulness, serving the purpose of slowing down cellular activity and diminishing arousal. Loss of control over drug intake or compulsive seeking and taking of drugs, despite adverse consequences. This occurs when a neuron is activated and temporarily reverses the electrical state of its interior membrane from negative to positive. Action PotentialĪn electrical charge that travels along the axon to the neuron's terminal, where it triggers the release of a neurotransmitter. A critical neurotransmitter that controls functions such as memory, attention, sleep, heart rate, and muscular activity.

Dendrite definition action potential