Acetylcholine (neurotransmitter): Functions And Characteristics
Nerve signal transmission is carried out through bioelectric impulses generated by neurons and transported from one to another until the message reaches its destination.
This transport depends largely on the action of neurotransmitters, substances that 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 to be identified is acetylcholine a substance we will talk about in this article.
Acetylcholine is a substance classified as an ester, made from compounds of an oxygenated acid and an organic radical. As I have already mentioned, it is the first neurotransmitter to be discovered, in 1914, and the different elements that are responsible for its synthesis and elimination. They make up the so-called cholinergic system
Acetylcholine is primarily seen as an excitatory neurotransmitter but it can also exert an inhibitory action depending on the type of synapse in which it acts.
On the other hand, acetylcholine is considered to be one of the main neurotransmitters of the nervous system and one of the most common, can be found throughout the entire brain and in the autonomic nervous system.
Synthesis
The synthesis of acetylcholine It occurs inside neurons, specifically in their cytoplasm through the union of acetic acid or acetyl-CoA and choline thanks to the enzyme cholinecetyltransferase.
After this, acetylcholine is sent along the axon to the terminal button, where it will be stored until its use and release in the synaptic space
Acetylcholine receptors
The action of acetylcholine occurs through its interaction with a series of receptors that react to its presence in the different locations in which 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, that is, it requires the use of chains of second messengers to that allow the opening of ion channels This implies that its action is usually slow and has a longer 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 inhibitory
Nicotinic receptor
This type of receptor, which also has an affinity for nicotine, is ionotropic, which generates a rapid response by the receptor that allows the immediate opening of the channel. Its effect is fundamentally excitatory. They are usually found in the connections between neuron and muscle
Neurotransmitter degradation
Most neurotransmitters are received by the presynaptic neuron after being emitted. In this sense, acetylcholine has the peculiarity that it is not reuptaken but is degraded by the enzyme acetylcholinesterase present in the synapse itself.
Acetylcholine has a very short lifespan in the synapses because it degrades very quickly.
Principal functions
Acetylcholine is a neurotransmitter that can be excitatory or inhibitory depending on the receptors and the location in which it is released. It can act in different places and have different functions for the body, some of the main ones being the following.
Voluntary movement of muscles It requires the action of acetylcholine to be carried out, by causing the muscle contractions necessary for movement. In this aspect, the functioning of acetylcholine is excitatory, acting through ionotropic receptors.
2. Activity of the autonomic nervous system
Acetylcholine is one of the main components through which our body can prepare itself for action when faced with different stimuli or deactivate itself once the threat has ceased. This neurotransmitter acts at the preganglionic level, that is, in the transmission of nerve impulses between spinal cord and ganglion both in the sympathetic and parasympathetic systems.
In the parasympathetic system, this action also occurs at the postganglionic level, between the target organ and the ganglion. In the case of the parasympathetic system we can observe how the action of acetylcholine produces an inhibitory effect. Among other actions allows the heart rate to decrease as well as increasing the action of the intestines and visceral functioning.
3. Paradoxical dream
Paradoxical sleep or REM sleep is affected by the action of acetylcholine, which participates in the structure of sleep and gives it different distinctive characteristics.
4. Hormone production and management
Acetylcholine also has neuroendocrine function in the pituitary since 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 the level of consciousness. Acetylcholine causes that the cerebral cortex remains active and allows learning
Acetylcholine is also a substance of great importance when it comes to form memories and configure our memory participating in the management of the hippocampus from this area.
