• Nerve cells, called neurons, are one of the
building blocks of behavior.
• Neurotransmitters are the body’s natural
chemical messengers which transmit
information from one neuron to another.
• When an electrical impulse travels down
the body, or axon, of the neuron, it releases
• Neurotransmitters are stored in the
neuron’s terminal buttons.
• Neurotransmitters shows a range of
different effects on human behaviour.
About 50 neurotransmitters have been discovered so far. Out of
these, a few of the most important neurotransmitters and their
functions are discussed below.
This neurotransmitter was discovered in the year 1921, by Otto Loewi. It is mainly responsible
for stimulating muscles. It activates the motor neurons that control the skeletal muscles. It
is also concerned with regulating the activities in certain areas of the brain, which are
associated with attention, arousal, learning, and memory. People with Alzheimer's disease
are usually found to have a substantially low level of acetylcholine.
Dopamine is the neurotransmitter that controls voluntary movements of the body, and is
associated with the reward mechanism of the brain. In other words, dopamine regulates the
pleasurable emotions. Drugs like cocaine, heroin, nicotine, opium, and even alcohol increase
the level of this neurotransmitter. A significantly low level of dopamine is associated with
Parkinson's disease, while the patients of schizophrenia are usually found to have excess
dopamine in the frontal lobes of their brain.
Gamma-aminobutyric Acid (GABA)
GABA is an inhibitory neurotransmitter that slows down the activities of the neurons, in
order to prevent them from getting over excited. GABA is a non-essential amino acid, that is
produced by the body from glutamate. A low level of GABA can have an association with
anxiety disorders. Drugs like Valium work by increasing the level of this neurotransmitter.
Alcohol and barbiturates can also influence GABA receptors.
Glutamate is an excitatory neurotransmitter that was discovered in 1907 by Kikunae Ikeda of
Tokay Imperial University. It is the most commonly found neurotransmitter in the central
nervous system. Glutamate is mainly associated with functions like learning and memory. An
excess of glutamate is however, toxic for the neurons. An excessive production of glutamate
may be related to the disease, known as amyotrophic lateral sclerosis (ALS) or Lou Gehrig's
Epinephrine and Norepinephrine
Epinephrine (also known as adrenaline) is an excitatory neurotransmitter, that controls
attention, arousal, cognition, and mental focus. Norepinephrine is also an excitatory
neurotransmitter, and it regulates mood and physical and mental arousal. An increased
secretion of norepinephrine raises the heart rate and blood pressure.
Endorphins are the neurotransmitters that resemble opioid compounds, like opium,
morphine, and heroin in structure. The effects of endorphins on the body are also quite
similar to the effects produced by the opioid compounds. In fact, the name 'endorphin' is
actually the short form for 'endogenous morphine'.
Like opioids, endorphins can reduce pain, stress, and promote calmness and serenity. The
opioid drugs produce similar effects by attaching themselves to the endorphin receptor
sites. Endorphins enable some animals to hibernate by slowing down their rate of
metabolism, respiration, and heart rate.
It is the hormone produced by the pineal gland that also acts as a neurotransmitter. It
basically controls the sleep-wake cycle. It is also associated with controlling mood and
sexual behavior. The production of melatonin is dependent on light. Light to the retina inhibits
the production of melatonin, while darkness has a stimulating effect on its production.
It is a gas that acts both as a hormone and neurotransmitter, depending on the specific
requirement. It can cause the blood vessels to dilate, besides preventing the formation of
clots. This in turn, can promote the circulation of blood. Nitric oxide can increase the level of
oxygen in the body, and improve memory, learning, alertness, and concentration. It is also
responsible for causing the smooth gastrointestinal muscles to relax.
Serotonin is an important inhibitory neurotransmitter, which can have a profound effect on
emotion, mood, and anxiety. It is involved in regulating sleep, wakefulness, and eating. It plays
a role in perception as well. The hallucinogenic drugs like LSD actually bind to the serotonin
receptor sites, and thereby block the transmission of nerve impulses, in order to alter
sensory experiences. A significantly low level of serotonin is believed to be associated with
conditions like depression, suicidal thoughts, and obsessive compulsive disorder. Many
antidepressants work by affecting the level of this neurotransmitter.