2.3 What is a Neurotransmitter? – Definition, Types, Function & Examples
Neurotransmitters are chemical signals that can affect such feelings as mood, hunger, anxiety and fear. Let’s take a look at what happens inside your nervous system.
Inside your brain, muscles and glands, you have nerve cells called neurons that have the job of passing signals. An easy way to think of these cells is to imagine them as baseball players passing a baseball around the field. The ‘baseballs’ are the chemical signals that are thrown between the players. The neurotransmitters are thrown across the synaptic gap from one neuron’s terminal branch (or pitching hand) to another neuron’s dendrites (or catching hand). The catcher gets excited by the chemical signal, an electrical current travels through the pitching arm, or axon, and the terminal branches at the end of the axon fire off the neurotransmitters.
In the human body, there are billions of little neurons, and they’re not all the same. Some have short pitching arms and some have pitching arms up to three feet long! Some neurons throw neurotransmitters at the speed of one mph, and others throw fastballs up to 268 mph! Different neurons play different positions too. Your sensory neurons fire signals to your brain neurons, and your brain neurons in turn fire signals off to your motor neurons. Your nerves pass information about what you see and hear to your brain, which sends out signals to your muscles, so you can react. So when you see a ball flying through the air towards you, your brain neurons send signals to your arms to reach out and catch the ball.
The type of neurotransmitter that is fired depends on the function of the particular neuron firing it. On the receiving end, only certain types of neurons can receive these chemical signals. Neurons are team players, and each player has a position on the team.
Because the neurons that are receiving the neurotransmitters have different functions, neurotransmitters affect different types of behavior.
Types of Neurotransmitters
For example, your levels of the neurotransmitter serotonin regulate your appetite, sex drive, moods and ability to sleep. Low levels of serotonin may lead to anxiety or depression. Some anti-depressant drugs can help raise serotonin levels.
Other neurotransmitters control memory. Dopamine affects your ability to concentrate and learn. Dopamine levels also affect your ability to react and move. Dopamine deficiencies are found in patients with Parkinson’s disease. Symptoms include shaking and the inability to walk.
When you exercise, neurotransmitters called endorphins are fired from your gland neurons to your brain neurons and your spinal cord neurons to reduce pain and stress.
So, neurons are the cells that pass the information, and neurotransmitters are the chemicals that carry that information. The details of how these function are the continuing work of neuroscientists today.