Neurons, Hormones, and the Brain


So far, researchers have discovered about 15–20 different neurotransmitters, and new ones are still being identified. The nervous system communicates accurately because there are so many neurotransmitters and because neurotransmitters work only at matching receptor sites. Different neurotransmitters do different things.

NeurotransmitterMajor functionsExcess is associated withDeficiency is associated with
AcetylcholineMuscle movement, attention, arousal, memory, emotionAlzheimer’s disease
DopamineVoluntary movement, learning, memory, emotionSchizophreniaParkinsonism
SerotoninSleep, wakefulness, appetite, mood, aggression, impulsivity, sensory perception, temperature regulation, pain suppressionDepression
EndorphinsPain relief, pleasure
NorepinephrineLearning, memory, dreaming, awakening, emotion, stress-related increase in heart rate, stress-related slowing of digestive processesDepression
GABAMain inhibitory neurotransmitter in the brain
GlutamateMain excitatory neurotransmitter in the brainMultiple sclerosis

Agonists and Antagonists

Agonists are chemicals that mimic the action of a particular neurotransmitter. They bind to receptors and generate postsynaptic potentials.

Antagonists are chemicals that block the action of a particular neurotransmitter. They bind to receptors but can’t produce postsynaptic potentials. Because they occupy the receptor site, they prevent neurotransmitters from acting.