Classification of Neurohumoral Transmission

In this article, we will learn the different types of neurohumoral transmission. The process by which molecules can send signals from one place to another within a body is called neurotransmissions. In neurotransmissions, signalling molecules are often known as neurotransmitters released by the axon terminal of a neuron or the presynaptic neuron. They later connect and react with receptors on the dendrites of another neuron or the postsynaptic neuron, which is only a short distance away. Later, we will understand the role of acetylcholine in the process of neurohumoral transmission. 

Define Neurohumoral Transmission 

In simple words, neurohumoral transmission helps transmit or send signals from one nerve to another. In this way, every organ receives signals from our brain and is later transmitted via the spinal cord. A chemical neurotransmitter will be sent from a nerve terminal which will, in turn, respond to the particular receptors on the innervated cell in neuro-humoral transmission.

All the effector cells’ physiologic responses will only be triggered when the receptor is activated. Humoral releases a chemical messenger called neurotransmitters by nerves which helps them transfer messages across a synapse and neuroeffector junction.

The sections below are working of the transmission process:  

• The first conduction of axons takes place

• Neurotransmitters will synthesise and release

• There will be receptor activity

• Neurotransmitter catabolism

Classification of Different Neurotransmitters 

Neurotransmitters are called endogenous molecules that help transmit signals across a synapse from a neuron to a target cell. Many neurons only generate and release one type of neurotransmitter, but there might be some that can produce more than one at any given time. If there are more neurotransmitters, they will coexist at the synapse, and the cell will foresee several impacts simultaneously.

Neurotransmitters are classified based on chemical reactions. Also, further divided into numerous groups based on their molecular structure. Acetylcholine, biogenic amines, and amino acids are some of the commonly known neurotransmitters. The function can be classified into excitatory or inhibitory, whereas the activity of neurotransmitters can also be categorised into direct or neuromodulatory.

Acetylcholine

The first known neurotransmitter was acetylcholine. This neurotransmitter works on the neuromuscular junction and is composed of acetic acid and choline. These transmitters are released and attached to postsynaptic receptors before being destroyed by acetylcholinesterase. Acetylcholine works in the central nervous system, which also has acetylcholine-releasing neurons.

Norepinephrine

Norepinephrine is also called a stress hormone along with being a neurotransmitter. This hormone occurs naturally in the human body. It is the type of substance that sends signals between nerve cells. When the brain undergoes stressful situations, the signals are received, and these hormones are released into the bloodstream as stress hormones. These transmitters impact how our brain pays attention and responds to events as part of the body’s stress response. These transmitters, such as perform different functions  

• It can boost the heart rate

• Helps in increasing blood flow to muscles by triggering the release of glucose (sugar) into the circulation

Norepinephrine is also part of the central nervous system and helps improve alertness and arousal while also speeding up reaction time within the human body. Thus, these hormones play a pivotal role in altering different moods of human beings.

Amino acids 

Amino acid neurotransmitters are the most common and abundant neurotransmitters in the brain. These transmitters produce chemical and electrical synapses, which help connect specialised neuron biological structures and carry impulses across them in the nervous system. 

If there is successful transmission, it creates or blocks electrical impulses in a network of neurons. In the brain, glutamate is one of the predominant excitatory neurotransmitters. At the same time, GABA is the primary inhibitory neurotransmitter.

Epinephrine neurotransmitters

Epinephrine is a neurotransmitter and hormone used to treat allergic reactions, restore heart rhythm, and manage mucosal congestion, glaucoma, and asthma. Epinephrine, in layman’s language, is known as adrenaline. 

It is a type of hormone and a neurotransmitter that helps produce hormones in the adrenal glands. This hormone is administered as a medicine to treat issues such as hypersensitivity reactions. Epinephrine hormones have been available in an auto-injector (EpiPen) in the United States since 1987.

These transmitters can shift the blood to the tissues under stress. Epinephrine is needed by the human body in modest amounts to maintain cardiovascular homeostasis. For example, during cardiac arrest, patients must have increased blood flow through the coronary artery. In this case, epinephrine is injected into an intravenous fluid solution to help them raise their coronary artery pressure, allowing more blood to flow to the heart. 

Conclusion

In this article, we talked about the classification of neurohumoral transmission. Although there are 40 different types of neurons present in our nervous system, we are only talking about the essential ones like acetylcholine and dopamine. We also know what happens in neurohumoral transmission and how we receive messages impulsively.