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- Glossary
Anterior pituitary
The adenohypophysis is a gland and is also referred to as the "anterior pituitary gland." The adenohypophysis produces hormones such as prolactin and releases them directly into the blood, meaning it is endocrine. It is therefore involved in regulating numerous physiological processes. Together with the neurohypophysis, which is part of the brain, it forms the pituitary gland. The two systems are closely linked via a contact surface.
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- Glossary
Adrenaline
Along with dopamine and norepinephrine, it belongs to the catecholamines. Adrenaline, also known as epinephrine, is the classic stress hormone. It is produced in the adrenal medulla and causes an increase in heart rate and heartbeat strength, thus preparing the body for increased stress. In the brain, adrenaline also acts as a neurotransmitter (messenger substance), where it binds to so-called adrenoreceptors.
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- Glossary
Afferent nerve fiber
Afferent refers to nerve fibers that carry information to the central nervous system. Afferent nerve fibers transmit sensory information from the periphery, such as pain, temperature, touch, muscle tension, or organ activity, to the central nervous system. The opposite is efferent.
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- Glossary
Agnosia
The term agnosia comes from Latin and means "not knowing." It is a disorder of recognition caused by damage or dysfunction of the brain, without deficits in sensory perception. Agnosia is usually very specific, such as prosopagnosia, the inability to recognize a person by their face.
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- Glossary
agonist
Due to the lock-and-key principle, transmitters (messenger substances) can only bind to specific receptors. However, an agonist is chemically so similar to this transmitter that it can also bind to this receptor and thus trigger an identical response. Partial agonists, on the other hand, only trigger a weaker response, while inverse agonists bind to the receptor and inhibit its response.
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Accommodation
Change in the thickness of the lens of the eye by the ciliary muscles. This adjustment process increases the refractive power of the lens, allowing objects at different distances to be seen clearly.
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Action potential
In excitable cells (e.g., neurons or muscle cells), very rapid changes in electrical potential occur across the cell membrane. This event is the basis for signal conduction along the axon of the nerve cell. The action potential continues along the cell membrane and, according to the all-or-nothing principle, only occurs when the cell has been sufficiently excited.
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- Glossary
All-or-nothing principle
According to this principle, an electrical potential is only triggered in the cell when a certain threshold value of stimulus intensity has been exceeded. The response either occurs completely or not at all.
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- Glossary
Allocortex
A phylogenetically ancient region of the cortex (cerebral cortex) which, unlike the isocortex (also called neocortex), has fewer than six cell layers – in the hippocampus, for example, only three. The allocortex is divided into the paleocortex and archicortex, as well as the periallocortex, which is a transitional form between the allocortex and isocortex.
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- Glossary
Alpha waves
Neuroscientists distinguish between different types of brain waves based on their frequency. Alpha waves oscillate in the mid-frequency range between approximately 8 and 12 hertz. They occur, for example, in a relaxed waking state, such as when test subjects are tired or have their eyes closed, i.e., when there is no mental activity. In the brain, they originate primarily in the parietal lobe. They are also called "Berger's waves" Hans Berger, who first described them.
