Module 1.3-Unit 1: Neurons, Neural Communication, Endocrine System, Substance Use & Psychoactive Drugs

neuron

a nerve cell; the basic building block of the nervous sytem.

cell body

the part of a neuron that contains the nucleus; the cell’s life support center.

dendrites

a neuron’s often bushy, branching extensions that recieve and integrate messages, conducting impulses toward the cell body.

axon

the segmented neuron extension that passes messages through its branches to other neurons or to muscles or glands.

myelin sheath

a fatty tissue layer segmentally encasing the axons of some neurons; it enables vastly greater transmission speed as nueral impulses hop from one node ro the next.

glial cells (glia)

cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning, thinking, and memory.

action potential

a neural impulse; a brief electrical charge that travels down an acon.

threshhold

the level of stimulation required to trigger a neural impilse.

refractory period

in neural processing, a brief resting pause that occurs after a neuron has fired; subsequent action potentials cannot occur until the axon returns to its resting state.

all-or-none response

a neuron’s reaction of either firing (with a full strength response) or not firing.

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the recieving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft.

neurotransmitters

chemical messengers that cross the synaptic gap between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the recieving neuron, thereby influencing whether that neuron will generate a neural impulse.

reuptake

a neurotransmitter’s reabsorption by the sending neuron.

endorphins

“morphine within”; natural, opiod-like neurotransmitters linked to pain control and to pleasure.

agonist

a molecule that increases a neurotransmitter’s action.

antagonist

a molecule that inhibits or blocks a neurotransmitter’s action.

endocrine system

the body’s “slow” chemical communication system; a set of glands and fat tissue that secrete hormones into the bloodstream.

hormones

chemical messengers that are manufactured by the endochrine glands, travel through the bloodstream, and affect other tissues.

psychoactive drug

a chemical substance that alters the brain, causing changes in perceptions and moods.

substance use disorder

a disorder characterized by continued substance use despite resulting life disruption.

depressants

drugs that reduce neural activity and slow body functions.

tolerance

the diminishing effect with regular use of the same dose of a drug, requiring the user to take larger and larger doses before experiencing the drug’s effect.

addiction

an everyday term for compulsive substance use (and sometimes for dysfunctional behavior patterns, such as out-of-control gambling) that continue despite harmful consequences.

withdrawal

the discomfort and distress that follow discontinuing an addictive drug or behavior.

barbiturates

drugs that depress central nervous system activity, reducing anxiety but impairing memory and judgement.

opioids

opium and its derivatives; they depress neural activity, temporarily lessening pain and anxiety.

stimulants

drugs that excite neural activity and speed up body functions.

hallucinogens

psychedelic (“mind-manifesting”) drugs that distort perceptions and evoke sensory images in the absense of sensory input.

near-death experience

an altered state of consciousness reported after a close brish with death (such as cardiac arrest); often similar to drug induced hallucinations.