A neurotransmitter is any chemical that diffuses across a neural synapse, binds to receptors on a postsynaptic neuron, and causes changes in the cell's composition and/or behavior.
There are two types of neurotransmitters, excitatory and inhibitory.
an inhibitory neurotransmitter
An inhibitory neurotransmitter makes the postsynaptic neuron less likely to fire and propagate an action potential.
an excitatory neurotransmitter
An excitatory neurotransmitter makes the postsynaptic neuron more likely to fire and propagate an action potential.
How many neurotransmitters have been identified in the human nervous system?
More than 100.
Serotonin is an inhibitory neurotransmitter involved in the regulation of mood, sleep, appetite, and memory.
Serotonin is derived from the amino acid tryptophan.
Dopamine is an inhibitory neurotransmitter involved in mood, reward circuits, sleep, pleasure, and voluntary movement.
Dopamine plays a major role in the pathophysiology of Parkinson's disease and schizophrenia.
Norepinephrine is involved in the body's fight-or-flight response and the activation of the sympathetic nervous system; it acts to increase heart rate and blood pressure, trigger the release of glucose, and increase blood flow to skeletal muscles.
Norepinephrine is both a neurotransmitter and a hormone, and is commonly referred to as noradrenaline.
Epinephrine is involved in the activation of the sympathetic nervous system and assists in the body's fight-or-flight response; it works to regulate heart rate, blood pressure, air passage diameters, and metabolic shifts.
Epinephrine is both a hormone and a neurotransmitter, and is commonly referred to as adrenaline.
Acetylcholine is involved in muscle movements of both the autonomic nervous system, where it has an inhibitory effect on heart rate, and the somatic nervous system, where it has an excitatory effect on skeletal muscle action.
Acetylcholine also plays a role in REM sleep.
Glutamate plays a key role in the growth and development of neurons, and is highly involved in cognitive functions like learning and memory.
Glutamate is the most abundant excitatory neurotransmitter in the vertebrate nervous system.
GABA, short for gamma-Aminobutyric acid, regulates neuronal excitability, relieves anxiety and induces relaxation, and is also directly involved in the regulation of muscle tone.
GABA is the most abundant inhibitory neurotransmitter in the mammalian central nervous system.
Glycine acts as an inhibitory neurotransmitter, most commonly in the spinal cord, brain stem, and retina.
When acting as a co-agonist with glutamate, glycine is an excitatory neurotransmitter.
Beta-endorphin activates opioid receptors, resulting in significant pain relief and relaxation, particularly after physical trauma.
Opioid drugs, such as morphine, bind to the opioid receptors and produce similar effects to beta-endorphin.
Substance P is closely associated with the perception of pain and the body's inflammatory response, in which it serves as a vasodilator.
As a neurotransmitter, vasopressin deals with neurological functions such as social bonding and memory.
Vasopressin more commonly functions as a hormone, in which its major job is to increase water retention in the kidneys.
Histamine has a major role in the regulation of sleep and the process of forgetting.
The cells that fire histamine are most active during wakefulness and slowest during sleep.
Histamine is also involved in the body's inflammatory response, but does not act as a neurotransmitter in this capacity.
As a neurotransmitter, oxytocin encourages social bonding and maternal behavior.
Oxytocin more commonly functions as a hormone, in which it is most notably involved in uterine contractions during labor.