Neuro Glossary

On this page, you'll find a collection of technical terms you'll come across while surfing on this website and which you might confusing. They're both clickable in the articles they're mentioned and can be found here listed in an alphabetical order. Also, I'll try to explain medical terminology which you might encounter while communicating with your doctor or when reading medical reports. If I miss out on anything, please do not hesitate to This email address is being protected from spambots. You need JavaScript enabled to view it. and I'll implement it into my Neuro Glossary. 

Please note that, while I'm trying my best to put these rather complicated concepts into easy words, I have simplified the underlying processes in order to give you a rough idea of what these terms actually mean. I don't want to overburden you with complicated scientific facts. If you want to know more about the issues addressed here, please feel free to ask me, check out the books in the list of references at the end of the page or the further reading section.


A-D | E-H | I-K | L-O | P-S | T-W | X-Z



Adenosinetriphosphate (ATP): We have to consume sufficient amounts of energy, which we usually derive from the foods we eat, in order to be able to survive. Consequently, we don't just eat because we like the taste of what we're eating but, most importantly, since the foods we eat contain the energy we need in order to keep our organism alive. Our organism requires this energy to keep the various biochemical reactions going, which virtually take place in our cells all the time. Without these biochemical reactions taking place we would be dead. However, how does our body actually derive the energy it needs to keep it all going? Well, in order for our body to be able to obtain energy from the foods we eat, they have to be digested first, i.e. broken down into small molecules so they can be absorbed into the blood stream and used as energy1

Some of you might recall that, amongst other substances, the foods we eat contain different quantities of huge molecules called carbohydrates, proteins and lipids. These are all rather complex, huge molecules though and eating them alone does not supply your body with any energy yet. Consequently, while traveling through our digestive system (mouth, oesophagus, stomach, intestines etc.), these huge molecules are successively broken down into smaller molecules and become modified until eventually, they end up as ATP1. Metaphorically-speaking, one could say that ATP represents our body's, or more specifically, our cell's "energy currency" or "fuel" for biochemical reactions. 

ATP literally means adenosine triphosphate. In a series of complex biochemical reactions, our cells are able to synthesize ATP from glucose and biochemical intermediates derived from breaking down lipids and proteins1.

However, why do our cells actually use ATP (as opposed to glucose)?

ATP is a small molecule, which is basically a molecule called adenosine which has three phosphate groups attached to it. Whenever energy is required, and a special enzyme called ATPase is present, ATP reacts with water to adenosine diphosphate (ADP) and inorganic phosphate. This means that the bond which attaches the phosphate group to the adenosine molecule is cleaved and that's basically what yields energy. Even though this may sound highly complicated that's quite an easy thing to do for cells. If, each time a cell required energy, it had to break down glucose first, that would be quite inefficient and time-consuming. Compared to ATP, glucose is quite big molecule, which means that it would take up quite a large amount of space within a cell. Also, ATP can be converted to ADP and Pi and vice versa relatively easily, as opposed to glucose, which can't be synthesized that easily once it has been broken down. Consequently, ATP is more flexible1.

For all of you who like chemical reactions, this is the chemical reaction for the hydrolysis of ATP:

ATP + H2O ---> ADP + Pi 

Autonomic symptoms: These symptoms, which usually accompany cluster headache attacks, and tend to appear on the side of the attack, such as a tearing eye, a runny nose, a constricted pupil etc. are called autonomic symptoms4, because they are activated automatically by the autonomous nervous system. Consequently, they are autonomic reflexes, which we cannot control or suppress voluntarily. Furthermore, they emerge from both sympathetic (Horner's syndrome, constricted pupil etc.) and parasympathetic (tearing eye, runny/blocked nose, etc.) activation4.



EPSP: Excitatory postsynaptic potentials emerge when a neurotransmitter substance binds to a receptor located in a neuron's postsynaptic membrane and thus opens ion channels, which allow positively-charged ions (cations, usually Na+) to diffuse into the postsynaptic neuron. As a result, with positive charges diffusing into the neuron, the neuron's internal environment becomes "more positive" and therefore more likely to depolarise. This means that once enough EPSPs have arrived at the postsynaptic neuron, it is more likely to generate an action potential and consequently receive the signal from the presynaptic neuron5.



IPSP: Inhibitory postsynaptic potentials emerge when a neurotransmitter substance binds to a receptor located in a neuron's postsynaptic membrane and thus opens ion channels, which allow negatively-charged ions (anions, usually Cl-) to diffuse into the postsynaptic neuron and/or positively-charged ions (cations, usually K+) to diffuse out of the postsynaptic neuron. As a result, with negative charges diffusing into the neuron, the neuron's internal environment becomes "more negative" and therefore less likely to depolarise. Furthermore, if Kdiffuses out of the postsynaptic membrane, it additionally takes a great deal of positive charges out of the postsynaptic neuron, which basically has a similar effect, i.e. the neuron's internal environment becomes more "negative" than usual5

Ions: You might recall from chemistry that there are particles called atoms, which have a nucleus (consisting of protons and neutrons) and some kind of electron cloud surrounding the nucleus. Usually, atoms possess equal numbers of protons and eletrons, i.e. they are electrically neutral. If, for some reason, an atom loses an electron, it will become positively charged, because the number of positively charged protons outweighs the number of negatively charged electrons → this atom is now a cation (a positively-charged ion). Conversevely, if an atom gains an electron, it will become negatively charged, because the number of negatively charged electrons outweighs the number of positively charged protons → this atom is now an anion (a negatively charged ion)1.

Examples for ions which you may encounter on this website include, sodium ions (Na+)  potassion ions (K+) and chloride ions (Cl-).





Phospholipids: Normally, lipids are insoluble in water, i.e. they are hydrophobic ("afraid of water"). That's because they are usually uncharged molecules which cannot form hydrogen bonds with the water molecules. Phospholipids, however, are special lipids. They possess both a polar (water-soluble) head and a nonpolar (watter-insuble) tail1. Image 1.1 shows a simplified representation of a phopspholipid molecule.

Image 1.1: A phospholipid.

Due to its chemical properties, the head part of the molecule is hydrophilic ("water-loving") and therefore points toward the watery medium (either extracellular space or the cell's cytoplasm). Conversely, the tail part is hydrophobic ("afraid of water") and therefore tries to avoid the watery medium at all cost. This also explains why phospholipids arrange to form bilayers in eukaryotic cell membranes:

Image 1.2: The phospholipid bilayer.

Why is this so? Well, a water molecule (H2O) is made up of two atoms of hydrogen bonded covalently to one atom of oxygen. For reasons of electronegativity, which I won't explain here, oxygen has a tendency to drag electrons (negatively-charged particles) more towards itself, which is why the "oxygen end" of the molecule is slightly more negatively-charged, than the "hydrogen end" of the molecule. This is what makes the water molecule (H2O) a dipole. Consequently, the charged bit of the phospholipid (the polar head group) can form hydrogen bonds with the water molecule (and is therefore kind of soluble in water), whereas the hydrophic tail of the phospholipid is uncharged and therefore insoluble in water.

Proteins: Proteins are basically long chains of amino acids, which can adopt rather complicated, three-dimensional structures.They are also referred to as the "building blocks of life", because our DNA basically codes for how to build proteins. In a process called proteinbiosynthesis and in a series of complicated biochemical reactions, DNA is translated into a sequence of amino acids which is then assembled to make proteins of varying size and complexity. What is remarkable about this process is that tiny mistakes during the translation process or in the DNA molecule itself (e.g. caused by mutations) can have huge consequences on the side of the protein to be manufactured. These mistakes can lead to the protein folding in a wrong way so that it'll become unable to perform its job, e.g. membrane receptors becoming incompatible with the molecule they're supposed to bind to, red blood cells (erythrocytes) adopting a sickle-shaped appearance and therefore becoming unable to effectively transport oxygen, enzymes being unable to work etc3

Starch: Starch is a complex carbohydrate, a so-called polysaccharide. As opposed to glucose, which is monosaccharide, starch is basically a long chain of glucose molecules joined together by chemical bonds called 1,4-glycosidic bonds. An enzyme called amylase can cleave these bonds to split starch into its constituent glucose molecules so they can be absorbed into the blood stream and used by our cells to make ATP1. 

Receptor proteins (commonly abbreviated as "receptors"): Just as enzymes, receptors are basically very complex proteins folded in a very specific three-dimensional way so that only very specific molecules can bind to them. There are both extracellular and intracellular receptor molecules. Depending on the type of receptor, the binding of a molecule to its specific receptor can open certain ion channels or kick off a serious of complex biochemical reactions within the cell, which have various impact on the cell's metabolic activities, for instance. One good example for such a process is the binding of neurotransmitter molecules to specific receptors on ion channels in the postsynaptic membrane: once the neurotransmitter has bound to the receptor, the ion channel will open and allow for certain ions (either cations or anions) to diffuse into the postsynaptic neuron and consequently either instigate an action potential or not3.







1. Jones. M, Jones G. (1997): Advanced Biology. Cambridge Verlag

2. Roberts, M., Reiss, M., Monger, G. (2004): Advanced Biology. Nelson Verlag.

3. Campbell, N., Reece, J., Urry, L.A., Cain, M.L., Wasserman, S.A., Minorsky, P.V., Jackson, R.B. (2008): Biology (Eighth Edition). Pearson Benjamin Cummings Verlag.

4. May, A. (2006): Cluster Kopfschmerz und andere trigemino-autonome Kopfschmerzen. Neurologie 1: 2006.

5. Guyton & Hall (2010): Medical Physiology. Saunders.