Your body is more amazing and complicated than anything on this Earth; everything is tailored to work perfectly in synchronisation with everything else. From the beautiful complexity of the brain, to the admirably simple structure of the heart (in comparison), we are alive because of their cooperation and constant hard work. Most people pass through life unaware of the prodigious, intricate network of systems which constitute our anatomy.
Every system in the human body is specific to a function. From the skeletal system – providing rigidity, protection and structure to the body – to the circulatory system – keeping cells rich in oxygen and other essential nutrients using blood – we could not survive as we are without all fifteen systems*.
The Nervous System is one of those fifteen other systems, and is concerned with the transmission of electrical impulses and information. It is the nervous system that will make you feel that annoying poke from the person next to you, but also will initiate reflexes, such as when you touch a hot pan. In fact, ANY piece of information that needs to get from one place to another will be transferred thanks to the nervous system.
To understand neurotransmission, the anatomy of the neurones in the body must be understood.
Many of the features of a neurone are irrelevant to this article, but if you’re interested in knowing more, feel free to contact me.
The important parts to note are:
- The cell body – this contains the DNA for the structure and controls what the cell does.
- The dendrites – these receive information from other neurones, where they’re processed at the
- Axon hillock – this decides whether the received information is relevant, and whether an impulse should be sent.
- Axon – this is the pathway which the electrical impulses (hence information) travel.
- Terminal buttons – these are the most important for this post. It is here that neurotransmission takes place. They may also be called synaptic knobs, synaptic endings, axon terminals and many other names.
So what is the purpose of the terminal buttons?
Neurones are in every part of your body, so they need to branch off in all directions; it is not feasible to have one giant neurone that travels everywhere. As thousands of impulses are sent every second, this is another reason that we need so many neurones (just to illustrate, we have 20,000 neurones per mm³ in the brain – meaning approximately 10,000,000,000,000 in the brain alone).
This means, that with so many neurones in the body, they will need to transfer signals between each other so they reach their destination successfully. The terminal buttons are an important aspect of this process, known as neurotransmission.
The following video will provide a basic knowledge of the process, I highly advise you watch it before proceeding (it’s only 1 minute 19!).
As you can see, chemicals play a vital role in the transmission of signals. So what is the process?
- The impulse (action potential) arrives at the terminal button.
- Gated Ca2+ (calcium ion) channels open due to the electrical impulse, causing an influx of the ions.
- This influx causes synaptic vesicles to diffuse to the terminal button membrane and release the neurotransmitters inside.
- Once in the synaptic cleft, the neurotransmitters diffuse over to receptors on the post-synaptic neurone.
- The neurotransmitters then bind with the receptors. Only the correct neurotransmitters can bind to the receptors (much like a lock and key). The action potential is transferred to the post-synaptic neurone.
- The neurotransmitter is then destroyed with enzymes and recycled; it is reabsorbed into the pre-synaptic neurone, which is facilitated with uptake pumps. This allows the neurotransmitters to be used again next time.
Types of neurotransmitters: a brief overview.
So what are the most important neurotransmitters, and what do they do?
Neurotransmitters marked with a * have a large importance within Psychology.
This was one of the first neurotransmitters discovered. It’s main purpose is the stimulation or inhibition of movement in skeletal muscle. This neurotransmitter is usually found in the brain and peripheral nervous system. It has also been found to have impact on memory and learning. Other uses include slowing of the heart, contraction of the gut area and stimulation of mucus and saliva production.
Dopamine is the pleasure neurotransmitter. Drugs such as cocaine, ecstasy and alcohol stimulate the release of Dopamine, causing a feeling of happiness and stimulation (although alcohol is technically a depressant). In the brain, it actually controls movement, and can help with the regulation of information flow. People with Parkinson’s disease have a lack of Dopamine in the brain interior, causing motor problems. This neurotransmitter is important in Clinical Psychology, as Schizophrenics suffer a lack of Dopamine in the frontal lobe. This clouds their thinking and causes their distinct symptoms.
Noradrenaline (aka Norepinephrine)*:
This is involved in the regulation of mood. In Psychology, this is important as low levels of this can be a contributory factor of depression. Very high levels of this can cause stress and aggression; it is released in response to short-term stress and therefore causes the heart rate and blood pressure to increase. High levels of this, mixed with high levels of dopamine and phenylethalimine have actually been found to cause the infatuation emotion. When you’re feeling wildly in love, blame this mixture of neurotransmitters! Biologically, it increases levels of glycogen conversion in the liver, and conversion of fats to fatty acids. It also relaxes bronchial muscles, allowing easier breathing.
This is the prime neurotransmitter regulating mood, sleep, emotion and appetite. A large amount causes inhibition of appetite, small amounts cause cravings for food. Many people mistake Serotonin for Anandamide, which is what causes the food cravings and sleepiness when smoking cannabis. Serotonin in low levels has been linked to depression, and violent/aggressive behaviour.
Those are some of the main neurotransmitters, although there are many many more.
Relevance to Psychology
So why do Psychologists care about neurones and neurotransmission? Well as explained in the neurotransmitter section, lack/excess of some of them can contribute to psychological disorders, such as depression, schizophrenia and insomnia. Psychiatrists often have to prescribe medication to restore the balance between certain levels of neurotransmitters in the brain. Therefore, it is essential that Psychologists have an understanding of the nervous system and the chemical nature of the brain.
Further reading/viewing for the keen.
Favourite links are in bold.
http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php (HIGHLY recommended! ^^^)
Thanks for reading,