Neurotransmitters.2

Wow, there are over 50 known neurotransmitters, and I’ve just written short bios on eight of them. Notice any similarities between their functions? Besides acting in concert with one another, many of these chemicals also serve dual functions as hormones, which get released as the body responds to external stimuli.

Acetylcholine – movement, memory, neuron communication

Dopamine – movement, memory, information flow to higher levels of the brain, “feel good”

Epinephrine aka Adrenaline – “fight or flight”

Norepinephrine – memory, neuron communication, alertness, focus

Melatonin – circadian rhythms

Serotonin – “feel good”, calming, appetite, mood, transmission of nerve impulses

Endorphin – “feel good”, pain killer, stress reliever, positive feelings

Cortisol – memory, learning, “fight or flight”

So what can you do to keep your neurons firing at their peak? Well, it’s no different then what you can do to keep your overall body performing at its peak. Stay tuned for the next post, Food for Thought.

By the way, resources for my posts on neurotransmitters include web pages, which are usually referenced in the particular post, and the books by Sprenger and Jensen listed in the column to the right.

Cortisol

Think about something you remember well. Most likely that something produced an emotional response in you. Be it positive or negative, the more intense your emotional response, the stronger your memory of that particular event. It turns out that memories encoded through emotions are the strongest of all our memories.Cortisol gets released from the adrenal glands (located above the kidneys) in response to strong stimuli, especially if the stimuli causes you some stress, again either positive or negative. Research has shown that cortisol plays a role in memory and learning, although too much of it causes the opposite effect of not thinking or remembering clearly. When the brain perceives strong stress, cortisol partners with adrenaline to deal with fight or flight. A little bit of cortisol is helpful but too much of it can be detrimental.The Human Brain and Stress page at The Franklin Institute Science Museum contains informative explanations of the effects of noise on creating stress within the brain, and the impact of stress on memory and gender. About three-quarters along on the page you will find information about the role of Cortisol.

Endorphin

I teach computer classes to middle schoolers and maintain a bulletin board chock full of computer related humor. In the center is posted the rationale for the humor: science has shown if you smile or laugh wide enough to crinkle the corners of your eyes your body will release chemicals that make you feel good. Laughter IS good for you (Check out the U of E link below for more details.) Ah, endorphin, one of the “feel good” triplets, along with serotonin and dopamine.Not only does endorphin’s release make you feel good, but it also acts as a natural pain killer.Undergrads at the University of Edinburgh have put together an information site that sets to answer the query “Does Exercise promote good health?” Of particular interest is the page How Does Exercise Affect Our Mood?, which contains lots of information on endorphins and their stress relieving, pain killing, positive feeling impact.The Molecular Expressions site, noted for “exploring the world of optics and microscopy”, has some colorful images along with explanatory text in its Endorphin Collection. Just looking at the colorful images of endorphins might cause you to smile, which should remind you of endorphin’s feel good benefits.

Serotonin

Often called the “feel good” neurotransmitter, along with dopamine and endorphin, serotonin functions as a calming agent, and also impacts appetite and mood. Too much serotonin can lead to feeling overly calm or sleepy; too little can lead to increased aggression and feelings of depression.Serotonin is also very useful and important in assisting with the transmitting of nerve impulses in the brain. If you like the thought of your brain functioning smoothly, you can start to understand why it would be beneficial to maintain a “just right” balance of serotonin levels.There are a number of ways to naturally influence serotonin levels, and all of them will sound like “no–brainers” Positive feedback is one of the most effective ways to stimulate serotonin, followed by exercise (remember that “runner’s high” when Dopamine was discussed), smiling, listening to music, and singing. So sing along with serotonin and smile, smile, smile :-)For an interesting look at some of the neurotransmitters and how they both impact our lives and are impacted by our lives, check out Brain Chemicals and Modern Life on Teresa Gallagher’s Born to Explore site. An environmental scientist and mom, Teresa provides a slew of resources on the topic of ADD and ADHD.

Melatonin

As with many neurotransmitters, melatonin is also a hormone. And as with many neurotransmitters, melatonin seems to work in synch with other neurotransmitters, in this case serotonin, which will be discussed in my next post.Melatonin is responsible for our body rhythms, known as circadian rhythms, which boils down to our sleep and wakefulness cycles. These cycles are directly influenced by our exposure to light. As darkness sets in, melatonin is released, promoting the urge to go to sleep. Teenagers usually release melatonin at later times in the evening so they tend to fall asleep later and wake up later. There is no “early” in that description and the result is that teenager circadian rhythms are usually out of synch with school start times. The National Sleep Foundation has found that school start times should be altered to accommodate teenagers and thus promote more healthful patterns resulting in more beneficial learning environments.SAD (Seasonal Affective Disorder) results from exposure to too little sunlight in the fall and winter months. The Heschong Mahone Group did extensive research on the impact of daylight on performance, both in schools and in businesses. The results of their research show that natural light has a consistent and predictable positive effect on student performance. “The results of this study of student performance, when combined with the companion study showing the positive effect of skylighting on retail sales, also strongly support the thesis that these performance benefits from daylighting can be translated to other building types and human activities.”Dr John W Kimball, a former Tufts and Harvard professor, maintains an online biology text that has a simple exlanation of Melatonin and the Pineal Gland, including a link to The Circadian Clock in Mammals.

Norepinephrine

Norepinephrine is both a hormone and a neurotransmitter. When released as a hormone in response to excitement, which can include both positive and negative stimuli, norepinephrine also helps in cementing memories caused by the excitement.Norepinephrine’s role in responding to excitement may sound similar to Epinephrine, which I wrote about in my previous post. It turns out that norepinephrine is epinephrine that has reached the brain.When released as a neurotransmitter, norepinephrine helps carry messages across synapses. It also plays a role in retrieving memories, according to this Science Daily 2004 article about research at the University of Pennsylvania Medical Center.Norepinephrine is also useful in telling the brain to shake, rattle, and roll in an attempt to make the brain alert and focused. However, too high levels can be a cause of aggression. Serotonin, dopamine, and endorphin, working as a trio, can help balance high levels of norepinephrine and somewhat control the aggressive behavior.You can tinker with a 3D model of norepinephrine at the 3Dchem site, which focuses on chemistry, structures and 3D molecules and is maintained by Dr Karl Harrison from the Department of Chemistry at the University of Oxford.Folks with Parkinson’s have a decrease in production of norepinephrine. Marilee Sprenger, citing Wurtman & Suffes, 1996, notes that “Norepinephrine and dopamine, sometimes called the alertness chemicals, are produced when tyrosine reaches the brain. Tyrosine is found in protein.” That’s certainly a plug for having proteins in the diet. There will be more on what makes for a “really good brain diet” in a future post.

Epinephrine aka Adrenaline

I’ve always liked the way these two words conjure up mental images. Epinephrine brings to mind the Epi Pen, a potentially lifesaving device for people who deal with certain types of allergies. Adrenaline brings to mind the Road Runner of cartoon fame, cruising along at break neck speed.

Those images help explain epinephrine’s function, both as a hormone and neurotransmitter, to get the body revved up in response to a perceived threat or excitement. This response is known as “fight or flight” because adrenaline is released when the body perceives an event to which it needs to respond by “fight or flight”.

While not all excitement is negative, the body prepares itself just in case. Adrenaline is released in the adrenal glands (located above the kidneys and not in the brain) in reaction to a message begun in the amygdala. The amygdala does not waste time figuring out if something is a threat or not; instead it responds rapidly with the aim of protecting you if necessary. The signal goes from the amygdala to the hypothalamus to the pituitary gland (all of which are located in the brain) and then to the adrenal glands located mid-body. The adrenal glands then release adrenaline.Thus, your hands might get clammy before making a presentation or performing, and you might wish you could be invisible, but hopefully you are simply excited and not overly threatened, and you manage to go on with the show!

Dopamine

Dopamine functions both as a neurotransmitter and a hormone. It helps control physical movement and also helps regulate information flow to the higher levels of the brain, thus having low levels of dopamine may impact working memory and ability to focus. You might know someone who takes Ritalin. Well, that is a drug which is sometimes prescribed for people who have difficulty focusing because it counters the low levels of dopamine.

When tripled up with serotonin and endorphin, dopamine balances out high levels of norepinephrine, which can cause aggression. These three neurotransmitters also release into the brain when stimulated by exercise (think of a runner’s high, for instance), listening to music you like, smelling smells you enjoy (like freshly baked cookies), and receiving positive feedback, so you can understand why dopamine, serotonin and endorphin are thought of as the “feel good” chemicals.

There is a down side, though, to having naturally produced “feel good” chemicals in the brain. External elements often influence us and how we feel, and some of these elements can have negative effects on the body, such as too much alcohol or indulgence in other types of drugs. This is where addiction comes in to the story, as you can read in this University of Texas at Austin article.

From the Surfari wiki (which I co-authored with a colleague): Did you know that your brain is about 80 percent water? To keep it alert, it is good to drink water throughout the day. Another type of food that feeds your brain is protein. Protein provides amino acids, which help produce dopamine and norepinephrine. Sources of protein include yogurt and cheese (hey, this sounds like dairy products!), animal foods (chicken, meat, fish and eggs), and for those of you who prefer vegetarian foods (beans, lentils, nuts and seeds).

In Parkinson’s’ disease there are decreased quantities of dopamine which result in physical movements that are constant and jerky. An insufficient quantity of dopamine is also associated with Schizophrenia. The pharmaceutical L-dopa can sometimes help neurons to continue producing dopamine.

Acetylcholine

The chemical acetylcholine (ACh) is produced in an area just above the brain stem and is present throughout the brain. It is involved in voluntary and involuntary muscle movement, as well as in the formation of long-term memory. At night, when memory consolidation takes place, there are higher levels of acetylcholine present, and it turns out that many of our dreams are caused by this chemical. Most importantly, acetylcholine assists with communication from neuron to neuron.

So how do you make sure your brain is producing adequate amounts of acetylcholine? Choline is one of the ingredients that goes into producing acetylcholine and is found in eggs, salmon, liver, soy and lean beef. These foods all help raise choline levels because they contain lecithin, which has been connected to having a positive impact on memory recall. Hmm, it looks like not all fats are bad for your health and what you eat actually can make a difference to your brain’s health!

What happens if there are not proper quantities of acetylcholine? Apparently this is what happens to patients with Parkinson’s and Alzheimer’s diseases. Aricept is a drug that is possibly slowing the breakdown of acetylcholine in Alzheimer’s patients and you can see a video of how it is believed to work at the Aricept site.

Neurotransmitters

I imagine neurotransmitters as the grease that keeps the brain functioning much the same way that a well-oiled machine runs smoothly. Without neurotransmitters, communication between neurons does not happen. It is the neurotransmitters that carry nerve impulses across synapses from one neuron to the next.

When a neuron initially fires, it sends an electrical signal down its axon to the pre-synaptic terminal (also known as the end of the neuron and the end of the axon). The neurotransmitter’s task is to convert that electrical signal to a chemical signal and transmit it across the synapse to the dendrites of a nearby neuron. The nearby neuron’s dendrites contain receptors to receive that transmission, which convert the chemical signal into a new electrical signal.

For a visual explanation of how this process works visit the Mind Project’s Flash animation Introduction to Synapses. A consortium of educational institutions, the folks at The Mind Project are creating “curriculum materials that provide students with a challenging yet accessible introduction to the cognitive sciences (the study of the mind and brain).”

Back in 1921, Otto Loewi discovered the first neurotransmitter, Acetylcholine, and there are now some 50 or so known neurotransmitters. Over the next several posts we will explore some of the ones that just roll off the tongue (!): Acetylcholine, Dopamine, Epinephrine, Endorphin, Norepinephrine, Serotonin, Cortisol and Melatonin. Meanwhile you can check out some neurotransmitter tidbits at Neuroscience for Kids – Neurotransmitters.