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1. 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.

1. Glossary

cholinergic

Cholinergic neurons produce acetylcholine (an important neurotransmitter in the brain), and cholinergic synapses use it to transmit signals.

1. Glossary

Dopamine

Dopamine is an important neurotransmitter in the central nervous system that belongs to the catecholamine group. It plays a role in motor function, motivation, emotion, and cognitive processes. Disruptions in the function of this transmitter play a role in many brain disorders, such as schizophrenia, depression, Parkinson's disease, and substance dependence.

1. Glossary

Extinction

In extinction, a previously conditioned stimulus is presented several times without the originally paired reinforcement until the conditioned response subsides. For example, a dog has learned that the ringing of a bell announces food (conditioned stimulus → conditioned salivation response). In extinction, the bell is now rung several times without food following. After a few repetitions, the dog stops drooling when the bell rings: the conditioned response subsides. This decrease in response can also be detected at the synaptic level, for example, by a reduction in neurotransmitter release.

1. Glossary

GABA

GABA is an amino acid and the most important inhibitory neurotransmitter, which acts as a messenger in the transmission of information between neurons at their synapses.

1. Glossary

Glutamate

Glutamate is an amino acid and the most important excitatory neurotransmitter, which acts as a messenger substance in the transmission of information between neurons at their synapses.

1. Glossary

Inhibition

Neuronal inhibition describes the phenomenon whereby a sender neuron sends an impulse to a receiver neuron, causing the latter's activity to decrease. The most important inhibitory neurotransmitter is GABA.

1. Glossary

Mesolimbic pathway

A system of neurons that use dopamine as a neurotransmitter and play a crucial role in emotion, reward, and substance abuse. The cell bodies are located in the subtegmental area and extend to the amygdala, the hippocampus, and – most importantly – the nucleus accumbens, where they have their terminal buttons.

1. Glossary

Parkinson's disease

Parkinson's disease is one of the most common neurological disorders, caused by the death of dopamine-producing neurons in the substantia nigra, leading to a neurotransmitter imbalance in the basal ganglia. Symptoms usually begin late in life with mild tremors (resting tremor), increasing stiffness of the limbs, and slowed voluntary movements (bradykinesia). Later, postural instability, balance disorders, and difficulty walking occur. Other typical features include rigid facial expressions (hypomimia), a shuffling gait, and muscle stiffness (rigor). The disease is incurable, but its symptoms can be treated with medication (e.g., L-dopa, dopamine agonists) or surgery involving deep brain stimulation (brain pacemaker).

1. Glossary

NMDA receptor

NMDA receptors are specialized receptor channels in the membrane of nerve cells that only open under very specific conditions. First, the neurotransmitter glutamate must bind to the receptor, and second, the receptor needs a cofactor such as glycine or D-serine. In addition, the postsynaptic cell membrane must be depolarized so that the magnesium ion (Mg²⁺) normally located in the channel pore is removed. If these conditions are met, an ion channel opens in the center of the receptor and allows calcium ions (Ca²⁺) in particular, but also sodium ions (Na⁺), to flow into the cell, while potassium ions (K⁺) flow out of the cell. The cell can respond to the influx of calcium in a variety of ways. NMDA receptors enable the brain to modify synaptic connections throughout life. They are crucial for forms of synaptic plasticity such as long-term potentiation (LTP) and long-term depression (LTD) and thus play a central role in the formation and storage of memory content.