Chapter 6 Flashcards
Psychoactive Drugs
substances that act to alter mood, thought or behavior, are used to manage neuropsychological illness and may be abused
Route of Administration
way in which a drug enters and passes through the body to reach its target
Oral Administration
Easy and convenient; most complex route. Must be absorbed through the stomach lining or small intestine to enter the blood stream
In order to pass into the blood stream a drug must be….
soluble in water because blood has a high concentration of water
Gas or Aerosol Administration
penetrate the cell linings of the respiratory tract; are easily absorbed across these membranes into the bloodstream
Skin Administration
small molecule drugs penetrate the skin’s barrier (nicotine)
When obstacles are eliminated en route to the brain
the dosage of a drug can be reduced by a factor of 10
Blood-brain barrier
tight junctions between the cells of blood vessels in the brain that prevent the passage of most substances; protects the brain from many circulating hormones, toxic and infectious substances
Brain Capillaries–> Tight Junctions
Capillaries are formed by a single layer of endothelial cells; not fused in most parts of the body but ARE fused in the brain–> causing tight junctions
Where does the blood-brain barrier not exist?
postrema of the lower brainstem allows toxic substances in the blood to trigger a vomiting response; Pineal gland enables hormones to reach it to modulate day-night cycle; Pituitary is triggered in part by other hormones
What does the brain need to work?
oxygen, glucose, amino acids
How do essential molecules cross the BBB?
small molecules (oxygen and carbon dioxide) pass through the endothelial membrane; glucose, amino acids and other food components are carried across by active-transport systems (Ion-pumps-transporter proteins)
Catabolize
breaking down and removal of drugs by the body
What part of the body is especially important in catabolizing drugs?
Liver.
Drug neurotransmission at a synapse
- Synthesis of the neurotransmitter can take place in the cell body, axon or terminal 2. Storage of the neurotransmitter in granules, vesicles or both 3. Release of the transmitter from the terminal’s presynaptic membrane into the synapse 4. Receptor Interaction in the post synaptic membrane, transmitter acts on an embedded receptor 5. Inactivation of excess neutransmitter at the synapse 6. Reuptake into the presynaptic terminal for reuse 7. Degradation of excess neurotransmitter by synaptic mechanisms and removal of unneeded by-products from the synapse
Agonists
Drugs that increase neurotransmission
Antagonists
Drugs that decrease neurotransmission
Acetylcholine
agonists that excite muscles
Acetycholine Antagonists
Botulin Toxin (blocks release) Curare (blocks receptors)
Acetycholine Agonists
Choline-rich diets Black widow spider venom (promotes release) Nicotine (stimulates receptors) Physostigmmine (blocks inactivation) Organophosphates (blocks inactivation)
Tolerance
decrease in response to a drug with the passage of time
Three kinds of tolerance
metabolic, cellular, learned
Metabolic toelrance
number of enzymes needed to break down alcohol in the liver, blood and brain increases. As a result, any alcohol that is consumed is metabolized more quickly, so blood-alcohol levels are reduced
Cellular Tolerance
activities of brain cells adjust to minimize the effects of alcohol present in the blood