Module 2

Brain Regions: The Map

This module is a reference. Every drug class that follows targets specific regions — understanding side effects requires understanding what each region normally does.

Every side effect in every module traces back to altering one of these regions' normal jobs. Names aren't as important as recognizing the images and the basic function.

Reward & Addiction Circuit

Ventral Tegmental Area (VTA) — produces dopamine.
Nucleus Accumbens (NAc) — registers reward.

Normal job: assigns motivational value to behaviors that aid survival (food, sex, social bonding).

Disinhibition — a recurring mechanism in this course. When an inhibitory interneuron is itself inhibited, the neurons it normally suppresses become more active. Example: GABA interneurons in the VTA normally keep dopamine neurons quiet. Opioids silence those GABA interneurons — removing the brake — so dopamine neurons fire more. The drug never touched the dopamine neuron directly; it just removed what was holding it back.

VTA and NAc location in brain — Location in the brain.

Reward and addiction circuit — VTA and NAc — VTA and Nucleus Accumbens — the core reward circuit.

Brainstem (Survival & Overdose)

Medulla Oblongata — controls breathing and heart rate.
preBötzinger Complex — generates the inspiratory rhythm. Tells the diaphragm when to contract.
Parabrachial Nucleus — provides excitatory drive to the breathing rhythm.

Normal job: automatic, unconscious regulation of breathing in response to blood CO₂.

Memory aid: kinda looks like an upside-down ballsack.

Brainstem location in brain — Brainstem — location in brain.

Prefrontal Cortex (Impulse Control)

Normal job: logic, decision-making, future-planning. Functional brake against impulsive urges.

Prefrontal cortex location in brain — Location in the brain.

Prefrontal cortex diagram — Prefrontal cortex — the brain's decision-making center.

Extended Amygdala (Stress & Withdrawal)

Normal job: threat detection, anxiety, fear processing.

Extended amygdala location in brain — Location in the brain.

Extended amygdala diagram — Extended amygdala — stress and fear circuitry.

Hippocampus (Memory & Triggers)

Normal job: records spatial and contextual memory.

Hippocampus location in brain — Location in the brain.

Hippocampus diagram — Hippocampus — contextual memory storage.

Cortex Broadly

Normal job: general consciousness, sensation, thought.

Cortex location in brain — Location in the brain.

Cortex diagram — Cortex — the outermost brain layer handling conscious experience.

Cerebellum and Basal Ganglia

Normal job: motor coordination and movement. Also the ability to string actions together — like the sequence of throwing a ball, or providing context for a sentence.