Aim: How do drugs affect the brain?

The blood brain barrier is both a physical barrier and a system of cellular transport mechanisms. It

maintains homeostasis by restricting the entrances of potentially harmful chemicals from

the blood, and by allowing the entrance of essential nutrients.

Blood Brain Barrier

• The BBB is semi-permeable; that is, it allows some materials to cross, but prevents others from crossing.

General Properties of the BBB

• Large molecules do not pass through the BBB easily.

• Low lipid (fat) soluble molecules do not penetrate into the brain. However, lipid soluble molecules, such as barbiturate drugs, rapidly cross through into the brain.

• Molecules that have a high electrical charge to them are slowed.

The BBB can be broken down by:Hypertension (high blood

pressure): high blood pressure opens the BBB

Development: the BBB is not fully formed at birth.

Hyperosmolity: a high concentration of a substance in the blood can open the BBB.

Microwaves: exposure to microwaves can open the BBB.

Radiation: exposure to radiation can open the BBB.

Infection: exposure to infectious agents can open the BBB.

Trauma, Ischemia, Inflammation, Pressure: injury to the brain can open the BBB.

Adolescent brain development takes place in the frontal lobes

• Reasoning,

• Planning,

• Emotions,

• Problem-solving

RESEARCHERS FOUND THAT, OVERALL, GRAY MATTER VOLUME INCREASED AT EARLIER AGES, FOLLOWED BY

SUSTAINED LOSS AND THINNING STARTING AROUND PUBERTY, WHICH CORRELATES WITH ADVANCING

COGNITIVE ABILITIES.

Drugs can get into the brain when…

Hyperosmolity: a high concentration of a substance in the blood can open the BBB.

The drugs cause neurotransmitters (dopamine, serotonin and nor-epinephrine) to increase in the synapse producing an exaggerated effect (euphoria or depression)

Cocaine Addiction• Effects

Cocaine acts on the brain and is a highly addictive drug. Because crack is smoked, and allows high doses to reach the brain rapidly, crack is even more addictive. Both forms of the drug trap a chemical called dopamine in the spaces between the brain's nerve cells in a part of the brain called the reward system. Dopamine stimulates and re-stimulates these nerve cells, making the user feel intense pleasure. The brain responds to the overabundance of dopamine by destroying some of it, making less of it, and shutting down the cells' receptors so they can no longer receive dopamine's messages

Most drugs of abuse directly or indirectly target the brain's reward system by flooding the circuit with dopamine. Dopamine is a neurotransmitter present in regions of the brain that regulate

movement, emotion, cognition, motivation, and feelings of pleasure. The overstimulation of this system, which rewards our

natural behaviors, produces the euphoric effects sought by people who abuse drugs and teaches them to repeat the behavior.