UNIT 1 PART 1 — Biological Bases of Behavior (Expanded)

Monozygotic Twins

Identical twins who develop from a single fertilized egg; share 100% of their genes.

Dizygotic Twins

Fraternal twins who develop from two separate eggs; genetically similar to regular siblings.

Neurons

Basic nerve cells that transmit information throughout the nervous system.

Dendrites

Branching fibers that receive incoming messages from other neurons.

Axon

Long fiber that sends messages away from the neuron.

Myelin Sheath

Fatty tissue covering axons; increases the speed of neural impulses.

Action Potential

An electrical charge that travels down the axon.

Threshold

Minimum stimulation needed to trigger an action potential.

All-or-None Response

Neurons either fire at full strength or not at all.

Synapse

Gap between neurons where neurotransmitters are released.

Reuptake

Process where neurotransmitters are reabsorbed by the sending neuron.

Neurotransmitters

Chemical messengers that carry signals across the synapse.

Dopamine

Influences movement, learning, attention, reward; too much linked to schizophrenia, too little to Parkinson’s.

Serotonin

Affects mood, sleep, hunger; too little associated with depression.

Norepinephrine

Controls alertness and arousal; undersupply can depress mood.

GABA

Major inhibitory neurotransmitter; deficits linked to seizures and anxiety.

Glutamate

Major excitatory neurotransmitter; excess can cause migraines and seizures.

Endorphins

Natural painkillers linked to pleasure and pain control.

Agonist

Molecule that mimics or enhances a neurotransmitter’s action.

Antagonist

Molecule that blocks a neurotransmitter’s action.

Central Nervous System (CNS)

Brain and spinal cord; body’s main control center.

Peripheral Nervous System (PNS)

Connects the CNS to the body’s muscles and glands.

Somatic Nervous System

Controls voluntary movements of skeletal muscles.

Autonomic Nervous System

Controls involuntary functions (heartbeat, digestion).

Sympathetic Nervous System

Arouses the body for fight or flight.

Parasympathetic Nervous System

Calms the body and conserves energy.

Endocrine System

Slow chemical communication system using hormones.

Hormones

Chemical messengers produced by endocrine glands.

Pituitary Gland

Master gland; controls growth and influences other glands.

Adrenal Glands

Release epinephrine and norepinephrine during stress.

EEG

Measures electrical activity of the brain using electrodes.

MRI

Uses magnetic fields to show brain anatomy.

fMRI

Shows brain function AND structure by tracking blood flow.

Brainstem

Oldest brain region; controls basic survival functions.

Medulla

Controls heartbeat and breathing.

Pons

Coordinates movement; involved in sleep.

Reticular Formation

Controls arousal and alertness.

Thalamus

Sensory control center; directs information to sensory areas (except smell).

Cerebellum

Coordinates balance, movement, and implicit memory.

Limbic System

Emotion and memory center of the brain.

Amygdala

Linked to fear, aggression, and emotion.

Hippocampus

Processes new conscious memories.

Hypothalamus

Regulates hunger, thirst, body temperature, and reward.

Cerebral Cortex

Outer layer of the brain responsible for thinking and processing.

Frontal Lobe

Planning, decision-making, personality, movement.

Motor Cortex

Controls voluntary movement.

Parietal Lobe

Processes touch and body position.

Somatosensory Cortex

Receives touch sensations.

Occipital Lobe

Processes visual information.

Temporal Lobe

Processes auditory information and memory.

Corpus Callosum

Large bundle of fibers connecting the two hemispheres.

Split Brain

Condition where corpus callosum is cut, preventing hemispheres from communicating.

Plasticity

Brain’s ability to reorganize and adapt after damage or experience.

Neurogenesis

Formation of new neurons.

Psychoactive Drugs

Chemicals that alter perceptions and mood.

Depressants

Drugs that slow neural activity (alcohol, barbiturates, opiates).

Stimulants

Drugs that excite neural activity (caffeine, nicotine, cocaine).

Hallucinogens

Drugs that distort perceptions (LSD, marijuana).

Tolerance

Needing more of a drug to achieve the same effect.

Withdrawal

Discomfort/distress following discontinued drug use.

Addiction

Compulsive craving and drug use despite consequences.

Reward Pathway

Dopamine-based brain system involved in pleasure and addiction.