The main differences between hormone and neurotransmitter

Let's see how to distinguish between these two types of messenger substances present in the human body.

Our body needs hormones and neurotransmitters to function properly.

Neurotransmitters enable communication between neurons and other cells by crossing the synaptic space and by means of nerve impulses. Hormones, on the other hand, are secreted by the endocrine glands, intervening in the regulation of a multitude of basic bodily functions.

Although they share structural and functional characteristics, there are also aspects that differentiate them. In this article we explain what they are, how they act and what are the main characteristics of hormones and neurotransmitters. the main characteristics of hormones and neurotransmitters, as well as the most important differences between them..

Hormones: definition, characteristics and classification

Hormones are chemical substances that act as messengers and activate different processes for our organism to function correctly. They are produced in the endocrine or secretory glands (such as the hypothalamus, pituitary or thyroid glands, for example) and are released into the extracellular space, diffusing through the Blood vessels into the blood.

The main characteristics of these chemical messengers are that they are involved in metabolism and other functions (immune system, sexual reproduction, etc.); they act in tissues of the organism that may be at long distances from the point of origin from where the hormone is released; the effect they cause depends on the amount of hormones present, being directly proportional to their concentration.

Almost all hormones can be classified, chemically, into three large groupsThe following hormones are the most common: peptide hormones, composed of amino acids, polypeptides or oligopeptides, such as insulin or vasopressin; hormones derived from amino acids, which use these to synthesize themselves, such as adrenaline; and lipid hormones, of the eicosanoid or steroid group, such as cortisol and testosterone.

Hormones can produce stimulatory effects, promoting activity in a tissue (e.g. prolactin); inhibitory effects, decreasing activity (e.g. somatostatin, which inhibits the release of growth hormone); antagonistic effects, when two hormones have opposite effects on each other (e.g. insulin and glucagon); and synergistic effects, when two hormones together produce a more potent effect than separately (e.g. growth hormone and thyroid hormones).

Neurotransmitters: definition, classification and characteristics

Neurotransmitters are chemical substances used by our body to send information from one neuron to another through the synaptic space between them.through the synaptic space that mediates between them. These signals travel to and from the central nervous system, with the aim of coordinating our organism, regulating muscle activity, body secretions and the activity of different organs.

The chemical messengers that act as neurotransmitters share some basic characteristics: they are stored in synaptic vesicles, they are released when calcium ions (Ca2+) are introduced into the axon terminal in response to the action potential, and they produce their effect by binding to receptors on the membrane of the postsynaptic cell.

The main function of neurotransmitters is to inhibit or stimulate the activity of postsynaptic cells.depending on the type of receptor on which they exert their effect, triggering changes in the permeability of the neuronal membrane and in its enzymatic activity, mediated by other neuromodulators (such as cAMP and cGMP).

There are different types of neurotransmitters that can be classified as follows:

• AminesAmines: neurotransmitters derived from different amino acids. In this group we can include dopamine or serotonin.
• Amino acidsare the precursor substances of amines (e.g. glutamate or glycine).
• Purinessubstances such as ATP or adenosine can also act as chemical messengers.
• Peptidesdistributed throughout the brain, the best known are the opioid peptides (e.g. enkephalins and endorphins), responsible for modulating pain, among other functions.
• Gasesnitric oxide, the most representative, which produces vasodilatory effects.
• EstersIn this group, the most representative neurotransmitter, acetylcholine, is involved in the regulation of sleep or muscle activity, among many other functions.

Differences between hormones and neurotransmitters

Hormones and neurotransmitters share a basic characteristic in that they both act as chemical messengers involved in the regulation of different bodily functions. However, there are important differences between a hormone and a neurotransmitter, there are, however, important differences between a hormone and a neurotransmitter.. Below, we will see what they are.

One of the differences between hormones and neurotransmitters is that hormones are released by the endocrine glands into the bloodstream; neurotransmitters, on the other hand, are released by the endocrine glands into the bloodstream, neurotransmitters are released into the synaptic space between neurons. that exists between neurons. This leads us to point out another basic difference, and that is that the effect produced by hormones is, in general, much more prolonged than that of neurotransmitters.

Another characteristic that differentiates these two types of chemical messengers is that the neurotransmitter, when released, only communicates with the nearest neuron, only communicates with the nearest neuronHowever, hormones communicate with other cells that may be at a great distance, since they travel through the bloodstream. The difference also lies in the fact that neurotransmitters act specifically in the nervous system, whereas hormones could act anywhere in the body.

Sometimes the distinction between hormone and neurotransmitter is not entirely clear.. Some neurotransmitters also act as hormones, as is the case with the catecholamines (adrenaline, noradrenaline and dopamine). These can be produced by the adrenal glands and released into the bloodstream, exerting a hormonal effect; and at the same time, they are released into the nerve endings, acting as neurotransmitters. In these cases, they are also called neurohormones.

According to the French physician, Roger Guillemin, a neurotransmitter would be nothing other than a paracrine secretion hormone (a type of cellular communication by chemical secretion), although due to their specific characteristics, they are usually considered to be a type of messenger other than a hormone.

At present, however, there are still there are still authors who consider that a hormone is any substance that is released by a cell to act on another cell, either close or distant, either near or far away.whether close or distant, and independently of its origin or location, as well as of the route used for its transport (blood circulation, extracellular fluid or synaptic space). The definitions of hormone and neurotransmitter thus remain open to interpretation.

Bibliographical references:

• Cuenca, E. M. (2006). Fundamentals of physiology. Editorial Paraninfo.
• Gómez, M. (2012). Psychobiology. Manual CEDE de Preparación PIR.12. CEDE: Madrid.
• Guyton-Hall (2001). Treatise on Medical Physiology.10th ed., McGraw-Hill-Interamericana.