NEUROTRANSMITTERS and HORMONES: Biological Approach

neurons

Nerve cells - the basic building block of the nervous system; there are about 86 billion of them in the human brain alone

neurotransmission

The process of transferring information from one neuron to another at a synapse by use of chemical messages and electrical signals

action potential

A neural impulse; a brief electrical charge that travels down an axon (which is the long threadlike part of a neuron along which impulses are conducted from the cell body to other cells)

neurotransmitters

Chemical messengers that (when released from vesicles), cross the synaptic gaps between neurons, transmitting information from one neuron to the next

examples of neurotransmitters

Acetylcholine, Dopamine, Serotonin, Norepinephrine, GABA, Glutamate

synapse

The junction gap between the axon terminal of the presynaptic neuron and the dendrite or cell body of the postsynaptic neuron

presynaptic neuron

Neuron that sends the signal

postsynaptic neuron

Neuron that receives the signal

excitatory neurotransmitters

Chemical messengers that increase the likelihood of a neuron firing an action potential (by binding to receptors on the postsynaptic neuron), promoting communication between nerve cells (key examples include glutamate, acetylcholine, serotonin and dopamine)

inhibitory neurotransmitters

Chemical messengers that reduce the likelihood of a neuron firing an action potential (by linking to ion channels that allow negatively charged ions to enter the cell), thereby decreasing neural activity (key examples include GABA and glycine)

dopamine

An excitatory neurotransmitter associated with movement, attention and learning, and the brain's pleasure and reward system

serotonin

An inhibitory neurotransmitter that affects mood, hunger, sleep and arousal. Undersupply is linked to depression.

agonists

Molecules that bind to a receptor and activate a response (increasing or decreasing the activity of that cell accordingly)

endogenous

Growing or originating from within an organism (Example: Neurotransmitters, Hormones, etc.)

endogenous agonists

Neurotransmitters - because they are biologically already part of the nervous system and they bind to their matching receptor sites (Example: Acetylcholine attaches to ACh receptor sites on the postsynaptic neuron)

antagonists

Molecules that bind to a receptor but do not activate it; instead, they block the binding of agonists and prevent the receptor from being activated (Example: Scopolamine blocks acetylcholine receptor sites)

exogenous

Something that comes from an external source, not from within the body or cell (Example: Medicine or drugs)

reuptake

Process by which neurotransmitters are reabsorbed back into the synaptic vesicles of a neuron

hormones

Chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues (but some of them act as neurotransmitters within the brain)

examples of hormones

Cortisol, Oxytocin, Testosterone, Melatonin

endocrine system

The body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream