Acetylcholine (neurotransmitter): functions and characteristics

The nerve signal is transmitted by bioelectric impulses generated by neurons and transported from one to the other until the message reaches its destination.

This transport depends largely on the action of neurotransmitters, substances which are transmitted from one neuron to another through synapses and cause an excitatory or inhibitory effect on the postsynaptic neuron.

One of these neurotransmitters and in fact the first identified is acetylcholine, Substance that we will talk about in this article.

Acetylcholine: a neurotransmitter

Acetylcholine is a substance classified as an ester, made from compounds of an oxygen acid and an organic radical. It is, as I already mentioned, the first neurotransmitter discovered, in 1914, and the various elements which are responsible for its synthesis and its elimination. they constitute the so-called cholinergic system.

Acetylcholine is primarily considered to be an excitatory-type neurotransmitter, But may also exert an inhibitory action depending on the type of synapse in the act.

On the other hand, acetylcholine is considered to be one of the main neurotransmitters in the nervous system and one of the most common, can be found throughout the brain and in the autonomic nervous system.

synthesis

Synthesis of acetylcholine it occurs inside neurons, especially in their cytoplasm, By the union of acetic acid or acetyl-CoA and hill thanks to the enzyme cholinacetyltransferase.

After that, the acetylcholine is sent along the axon to the terminal button, where it will be stored until its use and release into the synaptic space.

Acetylcholine receptors

The action of acetylcholine is given by its interaction with a series of receptors which react to its presence in the different places where this neurotransmitter acts. Specifically, we can find in the nervous system two main types of cholinergic receptors.

Muscarinic receptor

It is a type of metabotropic receptor, i.e. it requires the use of second messenger chains to which allow the opening of ion channels. This implies that their performance is generally slow and has a longer lasting effect over time.

This type of receptor is usually the one with the highest level of presence in the brain, as well as in the parasympathetic nervous system. They can have a performance both excitatory and inhibitor.

nicotine receptor

This type of receptor, which also has an affinity for nicotine, is ionotropic, which generates a rapid response of the receptor which allows the immediate opening of the channel. Its effect is fundamentally exciting. we usually find them in the connections between neuron and muscle.

Degradation of neurotransmitters

Most neurotransmitters are prescribed by the presynaptic neuron after they are released. In this sense, acetylcholine has the particularity of not being collected but of being degraded by the enzyme acetylcholinesterase present in the synapse itself.

acetylcholine it has a very short lifespan at the synapses because it degrades very quickly.

main duties

Acetylcholine is a neurotransmitter that can be excitatory or inhibitory depending on the receptors and where it is released. It can act in different places and have different functions for the body, some of the main ones being as follows.

1. Engine control

Voluntary movement of muscles it requires the action of acetylcholine to be carried out, by causing the muscular contractions necessary for movement. In this aspect, the function of acetylcholine is of the excitatory type, acting through ionotropic receptors.

2. Activity of the autonomic nervous system

Acetylcholine is one of the main components by which our body can prepare for action against different stimuli or turn off once the threat ceases. This neurotransmitter acts at the preganglionic level, that is to say in the transmission of nerve impulses between the spinal cord and the ganglion, In the sympathetic and parasympathetic systems.

In the parasympathetic system, this action also occurs at the postganglionic level, between the target organ and the lymph node. In the case of the parasympathetic system, we can observe how the action of acetylcholine produces an inhibitory effect. Among other actions helps decrease heart rate, As well as an increase in intestinal action and visceral functioning.

3. REM sleep

REM sleep or paradoxical sleep is affected by the action of acetylcholine, which participates in the structure of sleep and gives it different characteristics.

    4. Production and management of hormones

    Acetylcholine has it too neuroendocrine function of the pituitary gland, As its action causes an increase in the synthesis of vasopressin or a decrease in prolactin.

      5. Awareness, attention and learning

      The human being’s ability to learn through perception is largely mediated by the action of acetylcholine, as well as maintaining attention and even level of consciousness. Causes of acetylcholine that the cerebral cortex remains active and allows learning.

      6. Formation of memories

      Acetylcholine is also a substance of great importance for form memories and shape our memory, Participate in the management of the hippocampus in this area.

      7. Perception of pain

      The activity of acetylcholine is largely involved in the perception of pain.

      Bibliographical references:

      • Gómez, M. (2012). Psychobiology. CEDE PIR preparation manual 12. CEDE: Madrid.
      • Hall, JE and Guyton, AC (2006). Manual of medical physiology. 11th edition. Philadelphia, Pennsylvania: Elsevier.
      • Kandel, ER; Schwartz, JH and Jessell, TM (2001). Principles of neuroscience. Fourth edition. McGraw-Hill Inter-American. Madrid.
      • Katzung, B. (2007). Basic and Clinical Pharmacology, 10th Edition. Mc Graw Hill Medical.
      • Martín, AM and González, FJA (1988). Compendium of psychoneuropharmacology. Diaz de Santos editions.

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