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Psychoactive Drugs & The Brain

Psychoactive Drugs & The Brain. Psychoactive Substances & The Brain. Psychoactive substances enter the bloodstream via oral administration, inhalation, smoking, or injection

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Psychoactive Drugs & The Brain

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  1. Psychoactive Drugs & The Brain

  2. Psychoactive Substances & The Brain • Psychoactive substances enter the bloodstream via oral administration, inhalation, smoking, or injection • Psychoactive substances must somehow move from the blood to the brain in order for central nervous system effects to occur

  3. Blood & Brain • Not until late 1800s/early 1900’s did scientists discover a partition between blood & brain • When dyes injected into blood, brain unstained • When dyes injected into cerebrospinal fluid, blood & organs unaffected • Pramod Dash, PhD, UT Medical School: free educational resource (fig.11.1a, b) • Separation between the two is called the “blood-brain barrier”

  4. Blood-Brain Barrier • A “filter” mechanism • Prevents many substances crossing between blood & brain (Univ. MN PSYC1001, Section 23 Blog, 2011) • Is protective, to keep foreign materials away Illustration: Carol Donner, Tucson, AZ

  5. Blood-Brain Barrier • Barrier structure protects brain and blood from allowing foreign particles to cross • Very small molecules can get between cells • Fat-soluble substances are more likely to get through cell membranes • Chemical substances can also move across barrier if they have carriers • Some substances cross with help of receptors • Some areas of blood-brain barrier are weaker than others • Image (Nature.com) • Pramod Dash, UT Medical School (fig. 11.2)

  6. The Brain’s Reward Pathway • Parts of brain responsible for certain tasks • Reward pathway is activated when a person receives pleasure • Ventral tegmental area, nucleus accumbens, prefrontal cortex Source: National Institute on Drug Abuse (1996) The Brain & the Actions of Cocaine, Opiates, and Marijuana. Slide Teaching Packet for Scientists.

  7. Nervous System: Neuron • Basic unit = neuron • Dendrites receive electrical information • Soma/cell body processes electrical information • Axon sends electrical information down neuron • End of axon is terminal, which can translate electrical message into chemical message

  8. Communication Between Neurons • Neurons do not physically connect • Communication occurs in space between neurons: the synapse • When electrical impulse travels down axon of one neuron, a chemical is released, a neurotransmitter Image source: Neurevolution.net: Chronicling the Cognitive Revolution in Neuroscience

  9. Communication Between Neurons • Neurotransmitter binds to specific receptors in target neuron, like “lock and key” • The “capture” of neurotransmitter continues electrical communication • Neurotransmitter may excite target neuron • Neurotransmitter may inhibit target neuron Source: NIDA

  10. Communication Between Neurons • After the neurotransmitter connects to receptor, most is removed and returned: reuptake • How Transmission Works (NIDA)

  11. Communication is Complicated • Excitation or inhibition of target (postsynaptic) neuron • Dozens of neurotransmitters • Dopamine • Serotonin • GABA • Many receptors, specific to neurotransmitters • Neighboring neurons can also affect neurotransmission

  12. Effects of Psychoactive Substances on Neural Communication • Psychoactive substances can cause a release or increased release of neurotransmitter from a neuron (agonists) Source: BCSworthpublishers.com

  13. Effects of Psychoactive Substances on Neural Communication • Psychoactive substances can prevent a neuron from releasing, or reduce the release of, neurotransmitter (antagonist) Source: BCSworthpublishers.com

  14. Effects of Psychoactive Substances on Neural Communication • Psychoactive substances can mimic neurotransmitters, binding to their receptors (agonists) • Psychoactive substances can block neurotransmitter receptors, altering normal brain function (antagonist) • Psychoactive substances can block the reuptake of neurotransmitters, making effects of neurotransmitters linger (agonist) • Agonist and antagonist examples (apehrlichman.com)

  15. Effects of Psychoactive Substances on Neural Communication: Blocking Reuptake of Neurotransmitter

  16. Communication Between Neurons • Animationcocaine (Moyers on Addiction) • Animation, opiates (Moyers on Addiction) • Animation, alcohol (Moyers on Addiction) • Animation, amphetamines(The Brain from Top to Bottom) • Animation, How Prozac Works (Selective Serotonin Reuptake Inhibitors)(YouTube)

  17. Mouse Party (University of Utah) • Ecstasy • LSD • Marijuana

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