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Dose / Response

Dose / Response. 1) What must happen, physiologically speaking, in order for a drug (medicinal or illegal) to elicit (cause) a response ?. The drug must be absorbed into the user’s bloodstream . 2) What variables will the degree of response to a drug depend on ?.

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Dose / Response

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  1. Dose/ Response

  2. 1) What must happen, physiologically speaking, in order for a drug (medicinal or illegal) to elicit (cause) a response? • The drug must be absorbed into the user’s bloodstream

  3. 2) What variables will the degree of response to a drug depend on? • A physiological response to a drug will depend on the concentration of the drug in the bloodstream. This, in turn, depends on: • The amount of drug taken • The method of administration of the drug (snorting, injection, eating, inhaling)

  4. 3) Describe the type of response you would typically expect at very low drug doses. Explain your answer referring to the concept of neurotransmission. • No effect (or response) can be observed at very low drug doses. • This is because there is not enough of the drug in the brain to bind to the appropriate receptors and activate neurons of the reward system

  5. 4) Define drug threshold. Explain how this is different than drug tolerance • Drug threshold is the point at which there is enough of a drug in the bloodstream to elicit (cause) a response • Drug tolerance is when, after repeated usage of a drug, the body needs an increased dose in order to get the same physiological response.

  6. Drug dose/ response curve At low doses, no response Drug threshold

  7. 5) What happens to the effect (or response) caused by a drug as the amount of drug taken increases? • The response will increase proportionally with respect to the dose of the drug in the bloodstream.

  8. 6) Can a response elicited by a drug continue to increase infinitely? Explain your answer again referring to the principles of neurotransmission • At some point, the response to a given amount of drug will reach a plateau, or a maximum level. • This is due to saturation of receptors with neurotransmitter molecules. If all receptors on the postsynaptic neuron are occupied, increased levels of the drug in the synaptic cleft will not be able to further activate brain cells.

  9. Drug dose/ response curve PLATEAU despite increasing dose, response is steady At low doses, no response Drug threshold

  10. 7) What risks exist at very high drug doses? • When drugs of abuse are taken in extremely high doses they can cause a fatal response by halting respiration.

  11. How do Drugs get in the Body?

  12. 1) Who will experience the greatest effect of the drug? • Individuals whoinject the drug into a vein will experience the greatest effect from the drug as these individuals will have a higher concentration of the drug in the brain.

  13. 2. Who will experience the quickest effect from the drug? • The person who inhales the drug will experience the quickest effect from the drug (assuming the person inhales the whole 100 mg).

  14. 3. Who will experience the least effect from the drug? • The person who ingests, or swallows, the drug will experience the least effect.

  15. 4. Who will experience the slowest effect from the drug? • The person who ingests, or swallows, the drug will also have the slowest effect.

  16. 5. Tobacco smokers can use nicotine patches to help them quit smoking. The nicotine patches help the smoker slowly lower the amount of nicotine that enters the body. How does the nicotine in the patch enter the body? • Nicotine would enter the body by absorption through the skin.

  17. 6. Explain why the different ways of taking drugs cause different responses. a) Inhalation • Drugs that are inhaled (smoked) reach the brain the most quickly. • Inhaled drugs are absorbed into the blood in the lungs and then pumped to all parts of the body including the brain via systemic circulation

  18. b) Injection • Rapid increase in the drug level in the brain but slightly slower than inhalation • Drug goes first to the right side of the heart then to lungs (pulmonary circulation)  back to the left side of the heart finally to the brain and body(systemic circulation)

  19. c) Snorting/ snuffing • Absorption through the skin or mucous membranes. • Slower response because the drug has a an even longer path to travel before being circulated to the brain and body.

  20. d) Ingestion • Slowest onset of response • The drug goes into the digestive tract and then must pass through the walls of the stomach and intestine to enter the blood capillaries.

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