Blood Brain Barrier

What forms the BBB (Blood Brain Barrier)?

Endothelial cells joined by tight junctions, plus pericytes and astrocyte end-feet.

Mnemonic: "TEPA": Tight junctions, Endothelium, Pericytes, Astrocytes.

How does glucose cross the BBB?

Facilitated diffusion via GLUT1 transporters.

How do lipid-soluble substances cross?

Simple diffusion through the cell membrane.

Mnemonic: "fat gets in fast."

What are P-glycoprotein pumps?

Efflux pumps that push drugs/toxins back into the blood, a key reason many drugs fail to treat brain conditions.

Where is the BBB naturally weaker?

Circumventricular organs (e.g., area postrema), which sense blood chemistry directly.

Mnemonic: "circumventricular = circumventing the barrier."

Why is the BBB so important overall?

It keeps the brain's chemical environment stable, blocks toxins/pathogens, and stops peripheral neurotransmitters (like gut glutamate/serotonin) from flooding brain signaling.

What is the NMDA receptor?

A glutamate receptor that needs both glutamate binding AND depolarization to open. Central to learning and memory (long-term potentiation).

Mnemonic: NMDA needs "two keys": glutamate AND voltage.

What blocks NMDA at rest, and what removes the block?

A magnesium ion sits in the pore at rest; depolarization pushes it out, allowing calcium in.

Mnemonic: "Mg guards the gate until the cell says go."

What does calcium influx through NMDA cause?

Strengthens the synapse (long-term potentiation), the cellular basis of learning and memory.

What is the AMPA receptor's role?

Binds glutamate, purely ligand-gated (no voltage need), drives fast everyday excitatory signaling.

NMDA vs AMPA — key difference?

AMPA = fast, fires whenever glutamate is present. NMDA = slow, needs glutamate AND depolarization together.

Mnemonic: "AMPA is the alarm, NMDA is the lock that needs two keys."

What is dopamine's broad receptor role?

D1-type excites, D2-type mostly inhibits. Governs reward, motivation and movement.

Mnemonic: "D1 Drives forward, D2 Damps down."