psych key terms

nature vs nurture

question of how behavior and mental traits are shaped by genetic inheritance vs environmental experience

evolutionary psychology

approach that uses evolutionary principles to explain certain behavior/mental processes were adapted for survival/reproduction

natural selection

traits that improve survival/reproduction becoming more common in populations

eugenics

movement that tried to control human reproduction to improve the population based on genetic ideas

social darwinism

misuse of evolutionary ideas that claims social inequality reflects “survival of the fittest” rather than complex historical and social factors

twin studies

compares identical and fraternal twins to estimate genes vs environment influence on a trait

family studies

examines how traits appear in relatives to infer genetic and environmental influences

adoption studies

compares adopted children with their biological and adoptive parents to separate genetic from environmental effects

identical twins

twins who develop from single egg and shares 100% of genes

fraternal twins

2 separate eggs and share 50% of genes

nervous system

The body’s communication and control network that coordinates sensation, thought, and action through the brain, spinal cord, and nerves.

central nervous system (CNS)

The brain and spinal cord; processes incoming information and sends commands to the body.

peripheral nervous system (PNS)

All nerves outside the brain and spinal cord that carry sensory messages to the CNS and motor instructions back to the body.

somatic nervous system (SNS)

A division of the PNS that controls voluntary movements of skeletal muscles and carries sensory information from the skin and senses.

autonomic nervous system (ANS)

A division of the PNS that automatically regulates involuntary functions like heart rate, digestion, and pupil size.

sympathetic nervous system (fight or flight)

The ANS branch that prepares the body for stress by increasing heart rate, dilating pupils, and slowing digestion.

parasympathetic nervous system (rest and digest)

The ANS branch that restores calm and conserves energy by slowing heart rate and stimulating digestion.

neurons

Nerve cells that send and receive information using electrical impulses and chemical signals.

glial cells

Support cells that insulate, nourish, and protect neurons and help with cleanup and communication.

myelin sheath

A fatty insulating layer around some axons that speeds up neural impulses.

reflex arc

A fast, automatic pathway through the spinal cord that produces a response without first involving the brain.

sensory neuron

A neuron that detects incoming stimuli and carries information to the spinal cord or brain.

interneuron

A neuron in the spinal cord or brain that processes incoming signals and relays commands.

motor neuron

A neuron that carries instructions from the brain or spinal cord to muscles and glands.

resting potential

The stable, slightly negative charge inside a neuron when it is not firing.

threshold

The minimum level of stimulation needed to trigger a neuron to fire.

action potential

A brief electrical impulse that travels down an axon when a neuron fires.

all or nothing principle

A neuron either fires completely once threshold is reached or not at all — there are no partial firings.

depolarization

The influx of positive ions that reduces the neuron’s negative charge and starts the action potential.

refractory period

The brief reset time after an action potential when a neuron cannot fire again.

reuptake

The process of neurotransmitters being reabsorbed into the sending neuron after signaling.

multiple sclerosis

A disorder where damage to myelin slows or blocks nerve signals, causing movement and sensation problems.

myasthenia gravis

An autoimmune disorder where acetylcholine receptors don’t work properly, leading to muscle weakness.

dopamine

A neurotransmitter involved in reward, motivation, and motor control.

serotonin

A neurotransmitter that helps regulate mood, sleep, and appetite.

norepinephrine

A neurotransmitter that increases alertness and arousal, especially during stress.

GABA

The main inhibitory neurotransmitter that reduces neural activity.

glutamate

The most common excitatory neurotransmitter, important for learning and memory.

acetylcholine (ACh)

A neurotransmitter that enables muscle movement and supports learning and memory.

endorphins

Natural painkillers that also produce feelings of pleasure.

substance P

A neurotransmitter that carries pain signals from the body to the brain.

adrenaline (epinephrine)

A hormone that triggers the fight-or-flight response by boosting heart rate and energy.

leptin

A hormone that signals satiety and helps you feel full.

ghrelin

A hormone that increases hunger.

melatonin

A hormone that helps regulate the sleep–wake cycle.

oxytocin

A hormone linked with bonding, trust, and social connection.

agonists

Drugs that mimic neurotransmitters and activate their receptors.

antagonists

Drugs that block neurotransmitters from binding to receptors.

reuptake inhibitors

Drugs that prevent neurotransmitters from being reabsorbed, leaving more available in the synapse.

stimulants

Drugs that increase central nervous system activity and arousal.

depressants

Drugs that slow brain activity and body functions.

hallucinogens

Drugs that distort perception and can trigger sensory experiences without external input.

opioids

Pain-relieving drugs that produce euphoria by binding to endorphin receptors.

tolerance

Needing more of a drug over time to get the same effect

addiction

Compulsive drug seeking and use despite harmful consequences.

withdrawal

Physical and psychological symptoms that occur when a person stops using a drug.